Tag: Learning

Learning!

Learning is the process of acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences. 

Evidence that knowledge has occurred may see changes in behavior from simple to complex, from moving a finger to skill in synthesizing information, or a change in attitude.

The ability to know possess by humans, animals, and some machines. There is also evidence of some kind of knowledge in some plants.

Some learn immediately, induced by a single event (e.g. being burn by a hot stove), but much skill and knowledge accumulate from repeat experiences.

The changes induced by knowledge often last a lifetime, and it is hard to distinguish known material that seems to be “lost” from that which cannot retrieve.

Definition of learning for Students
1: the act of a person who gains knowledge or skill Travel is a learning experience.
2: knowledge or skill gained from teaching or study. They’re people of great knowledge.
-@ilearnlot.

  • How to Set Your Organize Priorities?

    How to Set Your Organize Priorities?

    There are specific skills and steps that you can learn to effectively manage multiple priorities and to actually assess which activities you need to work on first then next in order to tame your daily and weekly schedule. I’ve tried to organize the best time management advice I can find into one place and make it “research administrator-friendly.”

    The ability to prioritize is highly important in terms of achieving your goal. It helps you to identify and focus only on the essential tasks. It frees you from falling into procrastination or getting distracted by less important tasks. By harnessing this skill, you will be less stressed and a lot more organized and put-together.

    To become proficient in prioritizing, you can start by applying former U.S. President Dwight D. Eisenhower’s Urgent/Important Principle.

    Eisenhower’s Urgent/Important Principle

    In 1954, he mentioned that there are “two kinds of problems: the urgent and the important. The urgent are not important, and the important are never urgent.” In this sense, these two concepts can be defined as follows:

    Important tasks are those whose results lead to the achievement of our personal or professional goals.

    Urgent tasks require your immediate attention. However, they are typically related to the goal of someone else (such as your boss). Nevertheless, we focus on them more because there are negative consequences to not doing them right away.

    At this point, you may want to reflect on three things.

    First, identify which tasks or activities are most important to you. Are they in line with your goal? How far along are you in terms of accomplishing it?

    Second, look back on how you spend your time each day. Do you focus on what is urgent? Were you able to find time for what is important?

    Finally, consider how you can make time for what is important and still be able to do what is urgent. Alternatively, think about whether you can sacrifice what is urgent for what is important.

    One strategy that can help you focus on the important tasks first is to do them at the start of your day. The reason why this is effective is that you would still make time for what is urgent later on in the day. After all, you will always find a way to do what is urgent to avoid the consequence.

    Make sure to write down all your thoughts until you can flesh out a concrete plan out of them.

    The Pareto Principle

    It is easy to prioritize when you are in control of your time and resources. However, things take a more challenging turn when you are faced with many issues that will force you to make quick decisions.

    If ever you find yourself in this situation, then you can take a page out of Italian economist Wilfredo Pareto. According to him, eighty percent of the effects of most events come from twenty percent of the causes. To make his point clear, he explained two examples.

    The first one is that 80 percent of the properties in his homeland are owned by only 20 percent of the population. The second, on which his principle is initially based, is that 20 percent of the pea-pods in his garden held 80 percent of the peas produce.

    To this day, the Pareto Principle is being used by many professionals to gauge almost anything, such as by stating that 80 percent of a corporation’s sales come from only 20 percent of its products.

    Going back to the concept of Prioritization, you can apply the Pareto Principle by applying the following steps:

    1. Identify the main problems.

    Take note of every issue that is holding you back from achieving your goal or task. If you are working as a team, consult each member to get their own insights. You might also need to consult your progress chart.

    1. Determine the main cause of each problem.

    According to the concept of Root Cause Analysis, there are three common root causes behind any problem. These are Physical Causes, Human Causes, and Organizational Causes.

    When something breaks down or fails to operate due to some tangible or observable aspect, then it is due to a Physical Cause. One example is you being unable to finish a three-page report due tomorrow because your laptop computer crashed.

    If a person failed to do something, or did something wrong, then the problem is from a Human Cause. An example would be your co-worker failing to send you an email of the survey results for your report tomorrow.

    In situations where, despite the effectiveness of tools and the efficient skills of the people involved, the process itself caused the problem, then it is considered to be due to an Organizational Cause. One example is the pyramid scheme, in that the products are effective and the salespeople are passionate and trained. Yet, the system itself fails to be sustainable.

    Based on this perspective, it is easy to identify the root cause of some problems. However, if you find it a challenge to do so, then you should ask yourself these questions to help you deduce the issue until you can identify the root cause.

    What happened?

    How did it happen?

    Why did it happen?

    Will it happen again?

    Why or why not?

    1. Rearrange the problems in order of priority.

    After you have identified the root cause for each problem, you should then create another list of the same problems. Only this time, you will be enumerating them based on how important it is for them to be solved. This way, you will instantly know which one to focus on solving first before you move on to the second, third, and so on.

    1. Come up with the solutions.

    Now that you have analyzed and organized all the problems, the final step is to solve each of them. Start with the most important problem to be solved, and then brainstorm on the best steps to take to address it.

    Now that you know how to apply Eisenhower’s Urgent/Important Principle and Pareto’s Principle, you can choose from a variety of time management tools in organizing all this information. A simple chart on a spreadsheet should do the trick, and it can look something like this:

    Eisenhower’s Urgent/Important Principle

    Today’s List of Tasks

    Important Tasks Urgent Tasks

    Task 1 – 8:00 am to 9:30 am Task 1 – 11:00 am to 12:00 am

    Task 2 – 10:00 am to 10:30 am Task 2 – 1:00 pm to 3:00 pm

    Pareto’s Principle

    Ranking Problem Root Cause Solution:

    1 Problem A Root Cause A Solution A

    2 Problem B Root Cause B Solution B

    3 Problem C Root Cause C Solution C

    By using these tools, you will surely be able to get more tasks done throughout your day. Of course, this does not mean that these tools alone will enable you to focus on getting the job done. There will be times when we fail to focus on a task because of unexpected occurrences and distractions. However, you can overcome these challenges by improving your ability to concentrate. The next chapter can provide you with tips and strategies on how to do just that.

  • What is Means of Time Management?

     

    Time management is the process of planning and exercising conscious control over the amount of time spent on specific activities, especially to increase effectiveness, efficiency or productivity. It is a meta-activity with the goal to maximize the overall benefit of a set of other activities within the boundary condition of a limited amount of time, as time itself cannot be managed because it is fixed. So, what is the question: What is Means of Time Management?

    Explains, What is Means of Time Management? Meaning and Definition.

    Time management may be aided by a range of skills, tools, and techniques used to manage time when accomplishing specific tasks, projects, and goals complying with a due date. Initially, time management referred to just business or work activities, but eventually, the term broadened to include personal activities as well. A time management system is a designed combination of processes, tools, techniques, and methods. Time management is usually a necessity in any project development as it determines the project completion time and scope.

    A highly competitive and fast-paced world, time management is now easily recognized as one of the most essential survival skills. It is the key not just to achieve your biggest goals, but also ensure that you will get the quality of life that you desire. It is in fact so important that everyone from the most competitive sales representative to the multi-tasking single parent needs it.

    Strictly speaking, time management as a concept is defined as the conscious process of planning and controlling the amount of time spent on particular tasks. The better your time management skills are, the more productive, efficient, and effective you tend to be. In the past, it was implemented only in school- and work-related tasks, but now it can be used for any purpose.

    You can think of time management as an umbrella, and under it are a variety of tools, strategies, and methods. You can choose from and apply any of these until you are able to find the one that best suits your needs, preference, and personality.

    Nevertheless, whichever time management tool or strategy you choose, you should be able to comply with each of its five major dimensions:

    1. The priorities should be clearly established.
    2. The tasks carried out should be geared towards these priorities and explicitly explained.
    3. The time, energy, and resources spent on unimportant or non-urgent tasks should be reduced, if not eliminated.
    4. The system (including your surroundings and the tools you use) should be made conducive in order to enhance productivity, effectiveness, and efficiency.
    5. Motivational factors (such as rewards or sheer self-discipline) should be present to guarantee the fulfillment of the time-bound tasks.

    When you take a closer look at these five dimensions, you would notice that none of them would exist if one does not plan ahead of time.

    For instance, the first dimension is about highlighting your goals or priorities, while the second is about enumerating specific tasks related to these priorities. Describing a goal and coming up with a To-Do list related to that goal is the perfect example.

    The third dimension is about reducing or eliminating tasks that are not as important. This process is essential because time is fixed since everyone gets the same twenty-four hours daily. For instance, let us say you did create a list of task in line with your priorities. However, if there are too many tasks for the day, then you will need to pare down the list to the most important ones.

    The fourth dimension stressed the importance of ensuring that you have a well-organized system before you even begin with your tasks. One example of this is to clear out, clean, and organize your desk space if you are to use it to complete a certain task.

    Motivational factors or incentives are the emphases of the final dimension and for a good reason. It is important to return to the main reason as to why you even want to manage your time well for these priorities. It could be that you are motivated to complete the task because there is a monetary reward at the end. On the other hand, you might be doing the task because you want to improve your skills. Regardless of how you become motivated, it is therefore important to be motivated per see.

    Naturally, none of us is a robot who can simply move like clockwork. It is one thing to be highly organized, focused, and efficient at what you do. It is altogether another thing to be completely rigid without room for spontaneity. Therefore, it is best to maintain balance by managing your time well, but not letting the idea of it overwhelm your life.

    Now that you are familiar with the general concept of time management, you might be eager to explore some of its most effective tools and strategies. You can start with the next chapter, which will help you set goals efficiently.

  • All Cavemen Must Carry a Big Stick

    Understanding the Story of All Cavemen Must Carry a Big Stick. Booker T. Washington is credited with the statement, “Success is measured not so much by the position that one has reached in life as by the obstacles which he had to overcome while trying to succeed.”

    All Cavemen Must Carry a Big Stick

    Once, I was a guest on a talk radio show along with Michael McDonald, one of my students who had pulled himself out of the ghetto to become an attorney and a respected politician. Michael had done this despite seemingly overwhelming odds that were stacked against him. Mike was asked by the host why others also do not likewise pull themselves up by their own bootstraps. He replied that it was really tough to pull yourself up by your bootstraps when you had no boots. What a great answer. No matter what the Preamble to our Constitution states, all men (and women) are not created equal.

    We each are born into different environments, with different talents, financial means, intelligence levels and other distinct advantages… or disadvantages. Why do some, like Mike, despite the odds, manage to succeed? Why do some have different drives, ambition, attitudes and determination? When is all this determined? Is it in the womb or the first few years of life? The great speaker, Zig Ziglar says, “Great people are just ordinary people with extraordinary determination.” Man Cave Store, Over the years, I have found this to be true.

    I taught high school for sixteen and one-half years. As I reflect back on the kids that I taught, the ones that accomplished the most in life were the ones that I would never have selected to do so. They were the ones that were average kids with little opportunity and lots of drive, grit and determination. When our caveman friend went out to go hunting, he soon learned that to bring the game home, he had to carry a big stick and learn how to use it. They too had to learn to carry a big stick and lots of arrows in their quiver. Here are Cavemen’s stories.

    Cavemen Story One: 

    Bob graduated from high school with less than average grades. Never did he, or anyone else, expect him to go to college. He met their expectations by starting to work immediately after high school. Although he did not like school, he was really good working with his hands. He liked the immediate gratification of seeing his projects come to fruition. He enjoyed construction work and began his first job as a carpenter’s helper.

    In a few years, he borrowed money from a local bank and built his first house. Then, he built another…then another. Fifteen years after graduation, he built his first condominium and found that he could quadruple his return by building and reselling multiple units. Bob is now a millionaire but continues to build condominiums and commercial properties.

    Cavemen Story Two: 

    Eric, like Bob in the first Cavemen story, barely graduated from high school. If a vote was taken, he would have been selected as the most likely not to succeed. Also, like Bob, he enjoyed working with his hands. His first few jobs were working as a helper for an auto mechanic. He started working part time in construction and learned fast. He enjoyed the challenge and satisfaction of seeing a project completed. Before long, Eric quit his job as a mechanic’s helper and built his first house.

    Eric moved into the house an immediately began his second house. … then a third. … then a fourth. Before long, he was developing subdivisions in his hometown. He negotiated and signed a contract to build grocery stores all across the country for a regional food store chain. The rest is history. Eric is now a multi-millionaire and travels the world expanding his investments and counting his money.

    Cavemen Story Three: 

    Tom graduated from high school in the middle of his class. He was average at best and never attempted to go to college. Instead, he started to work selling televisions at a retail store in a strip mall not far from home. Tom enjoyed sales and got very good at it. While others were in college classes, Tom was learning from the school of hard knocks. He eventually left his job selling televisions and started to work as a salesman for an electronic company that supplied components to the company that manufactured the television sets.

    By the time that Tom’s classmates graduated from college and began to join the workforce, Tom had managed to buy the troubled electronics company. Before long, through Tom’s diligence, determination and perseverance, the company had recovered, and Tom sold it to his biggest competitor. He immediately reinvested his profits into other ventures, which included several radio stations, a restaurant chain and a regional health club chain. Tom now lives in one of the biggest houses in town and spends most of his time playing with his diversified portfolio.

    Story Four:

    John graduated from high school as the class favorite. He was always well-liked and popular. Most were surprised when John did not go to college. He, instead, started to work with his brother-in-law building commercial properties. They soon discovered that they could build high-rise apartments for government housing at hefty profits.

    One thing followed another and soon their company had grabbed the attention of others who wanted to purchase the company. Not long after, John and his brother-in-law sold the business and both retired. Since he was forty-years-old, John has done exactly what he wants to do each day. He has not worked in many years.

    Story Five: 

    Our fifth Cavemen story is the story of Mike McDonald, the young man mentioned earlier in this chapter. I take special pride in Mike’s story since I did play a small part in opening a door to get Mike started. Mike was a great kid in high school. Mike lived in the government housing projects and had witnessed many of the personal tragedies of others growing up there. He stood exposed at an early age to gangs, drugs, violence and crime.

    Mike was smart enough to remove himself from those who were bad influences on him. Mike was active in his church, played on the high school football team and made good grades. Upon graduation, he knew that the likelihood of a college education was not good. This is where I enter the picture.

    Mike had a job working at one of the Taco Bells in Huntsville. As fate would have it, one day I got a craving for a spicy bean burrito. When I entered the Taco Bell I saw Mike sweeping the floors. I asked him why he was not in college. After a short conversation and three burritos, I promised Mike that I would see if I could help him get into college. A few phone calls to Middle Tennessee State University and to State Farm Insurance in Murfreesboro, Tennessee, things were beginning to fall into place. I had worked my way through school at MTSU by working in the mail room at State Farm Insurance’s South Central Office.

    It was mere luck (Remember what I said about luck.) that the personnel manager remembered me (Although it had been nearly ten years.) and agreed to give Mike a job. A few weeks later, Mike was enrolled in MTSU and had a steady job at State Farm Insurance. He caught a greyhound bus to Murfreesboro with only ten dollars in his pocket. Four years later, he graduated with honors from MTSU and entered law school. While at MTSU, Mike earned a position as a split receiver on the football team and was the first black President of the student body.

    Since graduating, Mike has stood named the Most Outstanding Alumni and earned many post-graduate honors. One of his first jobs was as the legal counsel to the Governor of the state of Tennessee. He was later Registrar of Davidson County (Nashville), Tennessee where he served for many years. At this writing, Mike is an attorney in Nashville and a law professor at two universities, MTSU and Tennessee State University. Mike’s success truly touches my heart since he had the least opportunity of any student that I encountered yet, he accomplished the most.

    All of the above stories are true. Of those mentioned, only Mike McDonald had a college education. What did all the people in the stories above have in common? They all had determination, an overwhelming desire to achieve and great work ethic. They each overcame the odds to attain the things that each accomplished. As stated earlier in this book, work ethic is more important than a stack of college degrees. In the Cavemen stories above, each learned to carry a big stick, to fill their quiver, and they each had a passion for what they did.

    Here is a short story about determination:

    Cavemen stories, A young guard stood placed on guard duty for the first time. He stood instructed that no vehicle was allowed to enter the compound unless it had a certain identification number on it. As luck would have it, the first unmarked vehicle to approach the gate was that of a general. The General had total disregard for the young guard and instructed his driver to drive on through the gate. The young guard leaned inside the vehicle and politely stated, “I’m new at this, sir, and I really don’t know what to do. Who do I shoot first, you or the driver?”

  • Practice Does Not Make Perfect

    Practice Does Not Make Perfect

    Several years ago at the National Spelling Bee, one of the young ladies really excelled among the others in the competition. With a bright smile, she confidently spelled each word without hesitation. After she had won the contest, she was being interviewed by the television network and was asked how she became just an outstanding speller. She looked directly into the camera and stated, “My success is due to two things, God and Practice!”

    I spent the first sixteen and one-half years of my working life as an educator. Two particular coaches really stand out in my mind. One fellow would practice his football team hour upon hour, day upon day, week upon week. He would practice his team on weekends and holidays. His practice time ran for hours with disgruntled parents waiting in the parking lot to pick up their kids. He was known far and near as being a tough and demanding coach, a reputation which he treasured. His players seemed to always suffer from burnout and bad attitudes. This coach was known throughout the state as being a tough coach. The problem was he could never produce a championship team. In fact, he often struggled just to have a winning season! Then there was coach number two.

    Coach number two had a whole different philosophy. His practice times were short but compact. The attitudes among his players were great. Every drill had a purpose. His practice time was filled with fun things that developed skills and motivated his athletes. The parents of his athletes loved him; the school board loved him; the Booster Club loved him; and his players loved him. He was always in demand as a public speaker at civic clubs and coaching clinics. Guess what? He also always produced the best teams, winning seasons, and led the conference in athletic scholarships for his players.

    What was the difference in these two coaches? Coach number two had learned the secret of success. Contrary to Ben Franklin or whoever gets credit for the old saying… practice does not make perfect. Only “good” practice makes perfect! If a person does the same thing over and ever and over, but does it the wrong way, it is still wrong. That person is wasting his time, spinning his wheels and reinforcing the negative. A person has to determine the things that work and concentrate on strengthening and improving the little things that will enhance their success ratio. Doing the same thing over and over will produce the same results. If something is not working, then evaluate it (Remember the principals of management?), and make adjustments so that the results will be different. In the world in which we live, the winners have learned to do this whether it is in one’s personal life, business life, hobbies or in coaching!

    A person can find true peace and self-actualization through accomplishment. On the other hand, continuous failure leads to a very sad and unfulfilling life. There are so many people who continue to live their lives in a rut that leads to nowhere. They work in jobs that they do not like, with people that they cannot tolerate and in positions that are unrewarding. This is so sad since life is full of opportunity, excitement and adventure. Why would anyone stay in a situation in which they merely exist instead of flourish? Life has too much to offer for one to waste away his precious years and trade each day of his life for a paycheck! That is why entrepreneurs are different from other people. There is something in their inner being that will not allow them to merely survive.

    Zig Ziglar has inspired thousands upon thousands with his books and public appearances. I had the opportunity to meet Mr. Ziglar several years ago and found him to be even more dynamic in person as he is in his books and on his tapes. Zig believes, as I do, that a good attitude is the most important personal asset that a person possesses. One’s outlook on life determines how far he will go. One’s attitude determines how one reacts to the inevitable failures that even the most successful people have to overcome. As Zig states, “It’s not what happens to you that is important, but rather how you react to what happens to you.” How true this statement is! When things don’t go right, do you fall apart? Do you lash out and blame others? Do you wallow in your failure or do you pick yourself up, dust yourself off and continue to plunge forward? We have all heard the stories of Thomas Edison and the number of times that he suffered defeat and setbacks in his endeavor to invent the light bulb and some of his other inventions. We have all heard the stories of Col. Harland Sanders and how he only found success with his Kentucky Fried Chicken idea after he retired from what he really did for a living. We have heard the story of Garth Brooks who was rejected time and time again by the major record labels in Nashville before a chance appearance at the Bluebird Café turned his life around. Garth went on to be the biggest single country act in history! These type stories go on and on. Zig states that, “One’s attitude, not his aptitude, will determine his altitude.” How true this statement is for the aspiring entrepreneur?

    Over the years, I have discovered that entrepreneurs have a different outlook on life. There is the story about the young clerk in the department store who was approached by a customer who asked him if he was the manager. The young man looked up at the customer and quickly replied, “No sir! Not yet!” What a great answer! Just imagine if the young man had hanged his head and replied, “Oh no sir. Not me. I’m just a clerk.” What a different image that would have projected. There is another story about the two men who were both working side by side digging a ditch that was to be the foundation for a huge new palace. A passerby stopped and asked the first man what he was doing. Belligerently, he replied, “Can’t you see that I’m digging a ditch?” The passerby continued over to the second man and stated, “Well, I see that you are digging a ditch also.” “No sir”, replied the second man. “I’m building a palace!” Attitude! Attitude! Attitude!

    Once, several years ago, I was watching one of the local television stations in my home town of Huntsville, Alabama. The local news had had a contest among the regional junior high school students and had selected one of the students to co-host the weather forecast. The young man that won the contest gave his weather report along with the station’s meteorologist. After the report, the meteorologist conducted a quick interview with the young man. He asked him about his education and future ambitions. The meteorologist concluded his interview by asking him if one day he wanted to be the weatherman at the station. The young man paused, and with a perplexed look on his face replied, “No sir! One day I want to own this station!” I could not help but get a lump in my throat when I heard his answer. That is the attitude that this country desperately needs! Why work at the station when you can own the station? That is the mindset of the entrepreneur.

  • Are You Want to be a Caveman?

    Are You Want to be a Caveman?

    The caveman was the world’s first real entrepreneur. He had no choice. Either he got up, got his club, wandered into the woods, set his traps, killed something and drug it home each day, or he starved. He had to be able to out-run the fastest saber tooth tiger or he perished. There were no guaranteed salaries, pension plans, 401K’s, trade unions to protect him, deferred compensation programs, life and health benefit programs or Christmas turkeys or bonuses. The caveman had to perform each day, every day by the sweat of his brow and with his two hands and wit or he would not survive. Were there some cavemen who survived better and longer than others?

    A caveman is a stock character based upon widespread but anachronistic and conflated concepts of the way in which Neanderthals, early modern humans, or archaic humans may have looked and behaved. The term originates out of assumptions about the association between early humans and caves, most clearly demonstrated in cave painting. The term is not used in academic research.

    Sure there were! Some hunted longer, ran faster, got up earlier, learned to set better traps, learned to preserve their foods and prospered better than the others. These cavemen had the prettiest women, wore warmer furs, had better caves, bigger clubs and were envied and copied by the other cave people. Since mankind first came upon the earth, there were those who learned to excel over others. There always have been those who, through their willingness to take calculated risks, work harder, work smarter, work longer, develop their skills and improve themselves, achieve when others fail. This is true in the animal world. The biggest and strongest buck gets the doe. The fastest gazelle is never eaten by the lion. The smartest mouse is never caught in the trap no matter how large the cheese appears to be!

    Nothing has changed today except that the mentality of the caveman has been absolved by today’s modern world. Most people today would starve to death if they had to survive by killing something and dragging it home every day. Most would starve if they had to really work to make a living. Many todays had rather live with tremendous debt, work in jobs that they hate and with people that they despise and live in houses that they cannot afford than to roll up their sleeves and change their condition in life.

    Today, it is hard to listen to the radio without occasionally stumbling into one of those financial gurus on the talk radio stations out there. On every show, someone will call in to ask advice on the matter of personal bankruptcy. This person is always in debt because he has established habits of making one poor choice after another. He always has lived in houses that he could not afford, attended college on borrowed money, bought automobiles when he should have been walking and built up credit card and personal debt that was larger than his annual income. All of these callers want to declare bankruptcy. They are seeking advice as to how to get the process started. Almost none of them are willing to do the things necessary to eliminate the debt. What? Work two jobs! Nonsense! Work out a payment plan to systematically eliminate the debt. Not me! They just want to know how to wipe out the debt that they, under legal contract, legitimately owe. By doing so, they cross the magic threshold that converts them from a consumer to a thief!

    They are technically robbing a bank! They are absolutely no different than the person who straightens his mask, sticks a gun in a teller’s face then runs to a get-away car. They are doing exactly the same thing except that the bank robber deserves more respect since he is more honest in his intentions. A thief is someone who knowingly and willingly steals from others. If we would today again implement debtor’s prisons, there is no doubt that personal debt would drop to near zero. Mankind has become accustomed to the cushions afforded by this society. Today, there are few consequences for a person’s actions. Because of this, the caveman mentality of eat or be eaten has been lost. As our bankruptcy courts have proven, many have become lazy and had rather steal than to actually work to change their condition. What is as disappointing is that society has accepted this and places little or no shame on the actions of these people!

    This post is addressed to those who, like the cavemen of long ago, want to enter the world of entrepreneurship. This is a great country with opportunity hanging before each of us like a ripe, red apple ready for picking. There is no better place to be in the universe for those who want to enter the world of entrepreneurship. That world is not for the lazy, fainthearted, weak or unstable. It is for those who are willing to run ahead of the racers, to work longer, harder, faster and smarter. It is for those who are willing to break tradition, to color outside of the lines, to stand straight, to square their shoulders, swallow hard and kill something for the pot each and every day. It is for those who are not willing to live like everyone else. It is for those who do not want to be normal. It is for those who want to lift themselves above the crowd and, by their own two hands, shape and direct their future. If you fit this mold, then get on your feet, pick up your club, follow us as we welcome you to the brotherhood of the caveman and the greatest adventure of your life!

  • Meiosis and Gamete Formation

    Do you Know about Meiosis and Gamete Formation?

    Meiosis is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them. This process occurs in all sexually reproducing single-celled and multicellular eukaryotes, including animals, plants, and fungi. Errors in meiosis resulting in aneuploidy are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities.

    In meiosis, DNA replication is followed by two rounds of cell division to produce four potential daughter cells, each with half the number of chromosomes as the original parent cell. The two meiotic divisions are known as Meiosis I and Meiosis II. Before meiosis begins, during S phase of the cell cycle, the DNA of each chromosome is replicated so that it consists of two identical sister chromatids, which remain held together through sister chromatid cohesion. This S-phase can be referred to as “premeiotic S-phase” or “meiotic S-phase.” Immediately following DNA replication, meiotic cells enter a prolonged G2-like stage known as meiotic prophase. During this time, homologous chromosomes pair with each other and undergo genetic recombination, a programmed process in which DNA is cut and then repaired, which allows them to exchange some of their genetic information. A subset of recombination events results in crossovers, which create physical links known as chiasmata (singular: chiasma, for the Greek letter Chi (X)) between the homologous chromosomes. In most organisms, these links are essential to direct each pair of homologous chromosomes to segregate away from each other during Meiosis I, resulting in two haploid cells that have half the number of chromosomes as the parent cell. During Meiosis II, the cohesion between sister chromatids is released and they segregate from one another, as during mitosis. In some cases all four of the meiotic products form gametes such as sperm, spores, or pollen. In female animals, three of the four meiotic products are typically eliminated by extrusion into polar bodies, and only one cell develops to produce an ovum.

    Because the number of chromosomes is halved during meiosis, gametes can fuse (i.e. fertilization) to form a diploid zygote that contains two copies of each chromosome, one from each parent. Thus, alternating cycles of meiosis and fertilization enable sexual reproduction, with successive generations maintaining the same number of chromosomes. For example, diploid human cells contain 23 pairs of chromosomes including 1 pair of sex chromosomes (46 total), half of maternal origin and half of paternal origin. Meiosis produces haploid gametes (ova or sperm) that contain one set of 23 chromosomes. When two gametes (an egg and a sperm) fuse, the resulting zygote is once again diploid, with the mother and father each contributing 23 chromosomes. This same pattern, but not the same number of chromosomes, occurs in all organisms that utilize meiosis.

    Meiosis

    Most plant and animal cells are diploid. The term diploid is derived from the Greek diplos, meaning “double” or “two”; the term implies that the cells of plants and animals have pairs of chromosomes. In human cells, for example, 46 chromosomes are organized in 23 pairs. Hence, human cells are diploid in that they have a pair of 23 individual chromosomes.

    During sexual reproduction, the sex cells of parent organisms unite with one another and form a fertilized egg cell (zygote). In this situation, each sex cell is a gamete. The gametes of human cells are haploid, from the Greek haplos, meaning “single.” This term implies that each gamete contains half of the 46 chromosomes—23 chromosomes in humans. When the human gametes unite with one another, the original diploid condition of 46 chromosomes is reestablished. Mitosis then brings about the development of the diploid cell into a multicellular organism.

    The process by which the chromosome number is halved during gamete formation is meiosis. In meiosis, a cell containing the diploid number of chromosomes is converted into four cells, each having the haploid number of chromosomes. In human cells undergoing meiosis, for instance, a cell containing 46 chromosomes yields four cells, each with 23 chromosomes.

    Meiosis occurs by a series of steps that resemble the steps of mitosis. Two major phases of meiosis occur: meiosis I and meiosis II. During meiosis I, a single cell divides into two. During meiosis II, those two cells each divide again. The same demarcating phases of mitosis take place in meiosis I and meiosis II—prophase, metaphase, anaphase, and telophase—but with some variations contained therein.

    As shown in Figure 1, first, the chromosomes of a cell are divided into two cells. The chromosomes of the two cells then separate and pass into four daughter cells. The parent cell is diploid, while each of the daughter cells has a single set of chromosomes and is haploid. Synapsis and crossing over occur in the prophase I stage.

    Meiosis and Gamete Formation Stages

    Figure 1  The process of meiosis, in which four haploid cells are formed.

    The members of each chromosome pair within a cell are called homologous chromosomes. Homologous chromosomes are similar but not identical. They may carry different versions of the same genetic information. For instance, one homologous chromosome may carry the information for blond hair while the other homologous chromosome may carry the information for black hair.

    Meiosis Phases

    As a cell prepares to enter meiosis, each of its chromosomes has duplicated in the synthesis stage (S) of the cell cycle, as in mitosis. Each chromosome thus consists of two sister chromatids.

    Meiosis I: At the beginning of meiosis, I, a human cell contains 46 chromosomes, or 92 chromatids (the same number as during mitosis). Meiosis I proceeds through the following phases:

    Prophase I: Prophase I is similar in some ways to prophase in mitosis. The chromatids shorten and thicken and become visible under a microscope. An important difference, however, is that a process called synapsis occurs. Synapsis is when the homologous chromosomes migrate toward one another and join to form a tetrad (the combination of four chromatids, two from each homologous chromosome). A second process called crossing over also takes place during prophase I. In this process, segments of DNA from one chromatid in the tetrad pass to another chromatid in the tetrad. These exchanges of chromosomal segments occur in a complex and poorly understood manner. They result in a genetically new chromatid. Crossing over is an important driving force of evolution. After crossing over has taken place, the homologous pair of chromosomes is genetically different.

    Metaphase I: In metaphase I of meiosis, the tetrads align on the equatorial plate (as in mitosis). The centromeres attach to spindle fibers, which extend from the poles of the cell. One centromere attaches per spindle fiber.

    Anaphase I: In anaphase I, the homologous chromosomes or tetrads separate. One homologous chromosome (consisting of two chromatids) moves to one side of the cell, while the other homologous chromosome (consisting of two chromatids) moves to the other side of the cell. The result is that 23 chromosomes (each consisting of two chromatids) move to one pole, and 23 chromosomes (each consisting of two chromatids) move to the other pole. Essentially, the chromosome number of the cell is halved once meiosis I is completed. For this reason, the process is a reduction-division.

    Telophase I: In telophase I of meiosis, the nucleus reorganizes, the chromosomes become chromatin, and the cell membrane begins to pinch inward. Cytokinesis occurs immediately following telophase I. This process occurs differently in plant and animal cells, just as in mitosis.

    Meiosis II: Meiosis II is the second major subdivision of meiosis. It occurs in essentially the same way as mitosis. In meiosis II, a cell contains a single set of chromosomes. Each chromosome, however, still has its duplicated sister chromatid attached. Meiosis II segregates the sister chromatids into separate cells. Meiosis II proceeds through the following phases:

    Prophase II: Prophase II is similar to the prophase of mitosis. The chromatin material condenses, and each chromosome contains two chromatids attached by the centromere. The 23 chromatid pairs, a total of 46 chromatids, then move to the equatorial plate.

    Metaphase II: In metaphase II of meiosis, the 23 chromatid pairs gather at the center of the cell prior to separation. This process is identical to metaphase in mitosis, except that this is occurring in a haploid versus a diploid cell.

    Anaphase II: During anaphase II of meiosis, the centromeres divide and sister chromatids separate, at which time they are referred to as non-replicated chromosomes. Spindle fibers move chromosomes to each pole. In all, 23 chromosomes move to each pole. The forces and attachments that operate in mitosis also operate in anaphase II.

    Telophase II: During telophase II, the chromosomes gather at the poles of the cells and become indistinct. Again, they form a mass of chromatin. The nuclear envelope develops, the nucleoli reappear, and the cells undergo cytokinesis.

    During meiosis II, each cell containing 46 chromatids yields two cells, each with 23 chromosomes. Originally, there were two cells that underwent meiosis II; therefore, the result of meiosis II is four cells, each with 23 chromosomes. Each of the four cells is haploid; that is, each cell contains a single set of chromosomes.

    The 23 chromosomes in the four cells from meiosis are not identical because crossing over has taken place in prophase I. The crossing over yields genetic variation so that each of the four resulting cells from meiosis differs from the other three. Thus, meiosis provides a mechanism for producing variations in the chromosomes. Also, it accounts for the formation of four haploid cells from a single diploid cell.

    Meiosis in Humans

    In humans, meiosis is the process by which sperm cells and egg cells are produced. In the male, meiosis takes place after puberty. Diploid cells within the testes undergo meiosis to produce haploid sperm cells with 23 chromosomes. A single diploid cell yields four haploid sperm cells through meiosis.

    In females, meiosis begins during the fetal stage when a series of diploid cells enter meiosis I. At the conclusion of meiosis, I, the process comes to a halt, and the cells gather in the ovaries. At puberty, meiosis resumes. One cell at the end of meiosis I enters meiosis II each month. The result of meiosis II is a single egg cell per cycle (the other meiotic cells disintegrate). Each egg cell contains 23 chromosomes and is haploid.

    The union of the egg cell and the sperm cell leads to the formation of a fertilized egg cell with 46 chromosomes, or 23 pairs. Fertilization restores the diploid number of chromosomes. The fertilized egg cell, a diploid, is a zygote. Further divisions of the zygote by mitosis eventually yield a complete human being.

    Gamete

    Gametes are the cells that fuse together during sexual reproduction to form a new organism. This lesson covers what these cells are, what they do, and the end result of when they meet.

    Definition of Gamete

    Gametes are the reproductive cells used during sexual reproduction to produce a new organism called a zygote. The gametes in males and females are different. The male gamete is called sperm. It is much smaller than the female gamete and very mobile. It has a long tail, flagellum, that allows it to move towards the female gamete. The female gamete is called an egg or ova. It is much larger than the sperm and is not made to move.

    Formation of Gametes

    Both the male and female gametes are formed during a process of cellular reproduction called meiosis. During meiosis, the DNA is only replicated or copied one time. However, the cells are divided into four separate cells. This means that the new gamete cells have only half of the number of chromosomes as the other cells. So, during meiosis DNA or chromosomes are copied, then split into two cells (with one full set of chromosomes each), then again split into two more cells, leaving only half of the pairs of chromosomes in each new cell.

    These new cells with only half of the chromosomes will mature into the gametes. The gametes are haploid cells because they have only one set of chromosomes. When they unite they will join their single sets of chromosomes to make a complete set, and then they will be considered diploid cells. In the female, the eggs or ova mature in the female’s ovaries. The sperm will mature in the male’s testes.

  • Mitosis and Cell Reproduction

    What do you understand of Mitosis and Cell Reproduction?

    Cell Cycle

    The cell cycle or cell division cycle is the series of events that take place in a cell leading to its division and duplication of its DNA (DNA replication) to produce two daughter cells. In bacteria, which lack a cell nucleus, the cell cycle is divided into the B, C, and D periods. The B period extends from the end of cell division to the beginning of DNA replication. DNA replication occurs during the C period. The D period refers to the stage between the end of DNA replication and the splitting of the bacterial cell into two daughter cells. In cells with a nucleus, as in eukaryotes, the cell cycle is also divided into three periods: interphase, the mitotic (M) phase, and cytokinesis. During interphase, the cell grows, accumulating nutrients needed for mitosis, preparing it for cell division and duplicating its DNA. During the mitotic phase, the chromosomes separate. During the final stage, cytokinesis, the chromosomes and cytoplasm separate into two new daughter cells. To ensure the proper division of the cell, there are control mechanisms known as cell cycle checkpoints.

    Animal cell cycle
    Animal cell cycle

    The cell cycle involves many repetitions of cellular growth and reproduction. With few exceptions (for example, red blood cells), all the cells of living things undergo a cell cycle.

    The cell cycle is generally divided into two phases: interphase and mitosis. During interphase, the cell spends most of its time performing the functions that make it unique. Mitosis is the phase of the cell cycle during which the cell divides into two daughter cells.

    Interphase

    The interphase stage of the cell cycle includes three distinctive parts: The G1 phase, the S phase, and the G2 phase. The G1 phase follows mitosis and is the period in which the cell is synthesizing its structural proteins and enzymes to perform its functions. For example, a pancreas cell in the G1 phase will produce and secrete insulin, a muscle cell will undergo the contractions that permit movement, and a salivary gland cell will secrete salivary enzymes to assist digestion. During the G1 phase, each chromosome consists of a single molecule of DNA and its associated histone protein. In normal human cells, there are 46 chromosomes per cell (except in sex cells with 23 chromosomes and red blood cells with no nucleus and, hence, no chromosomes).

    During the S phase of the cell cycle, the DNA within the nucleus replicates. During this process, each chromosome is faithfully copied, so by the end of the S phase, two DNA molecules exist for each one formerly present in the G1 phase. Human cells contain 92 chromosomes per cell in the S phase.

    In the G2 phase, the cell prepares for mitosis. Proteins organize themselves to form a series of fibers called the spindle, which is involved in chromosome movement during mitosis. The spindle is constructed from amino acids for each mitosis, and then taken apart at the conclusion of the process. Spindle fibers are composed of microtubules.

    Mitosis

    The term mitosis is derived from the Latin stem mito, meaning “threads.” When mitosis was first described a century ago, scientists had seen “threads” within cells, so they gave the name “mitosis” to the process of “thread movement.” During mitosis, the nuclear material becomes visible as threadlike chromosomes. The chromosomes organize in the center of the cell, and then they separate, and 46 chromosomes move into each new cell that forms.

    In cell biology, mitosis is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. In general, mitosis ( the division of the nucleus) is preceded by the S stage of interphase (during which the DNA is replicated) and is often accompanied or followed by cytokinesis, which divides the cytoplasm, organelles and cell membrane into two new cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic (M) phase of an animal cell cycle the division of the mother cell into two daughter cells genetically identical to each other.

    Mitosis is a continuous process, but for convenience in denoting which portion of the process is taking place, scientists divide mitosis into a series of phases: prophase, metaphase, anaphase, and telophase (see Figure 1):

    Mitosis and Cell Reproduction Process

    Figure 1. The process of mitosis, in which the chromosomes of a cell duplicate and pass into two daughter cells.

    Types of Mitosis

    Types of Mitosis

    The primary result of mitosis and cytokinesis is the transfer of a parent cell’s genome into two daughter cells. The genome is composed of a number of chromosomes complexes of tightly coiled DNA that contain genetic information vital for proper cell function. Because each resultant daughter cell should be genetically identical to the parent cell, the parent cell must make a copy of each chromosome before mitosis. This occurs during the S phase of interphase. Chromosome duplication results in two identical sister chromatids bound together by cohesin proteins at the centromere.

    When mitosis begins, the chromosomes condense and become visible. In some eukaryotes, for example, animals, the nuclear envelope, which segregates the DNA from the cytoplasm, disintegrates into small vesicles. The nucleolus, which makes ribosomes in the cell, also disappears. Microtubules project from opposite ends of the cell, attach to the centromeres and align the chromosomes centrally within the cell. The microtubules then contract to pull the sister chromatids of each chromosome apart. Sister chromatids at this point are called daughter chromosomes. As the cell elongates, corresponding daughter chromosomes are pulled toward opposite ends of the cell and condense maximally in late anaphase. A new nuclear envelope forms around the separated daughter chromosomes, which decondense to form interphase nuclei.

    During mitotic progression, typically after the anaphase onset, the cell may undergo cytokinesis. In animal cells, a cell membrane pinches inward between the two developing nuclei to produce two new cells. In plant cells, a cell plate forms between the two nuclei. Cytokinesis does not always occur; coenocytic (a type of multinucleate condition) cells undergo mitosis without cytokinesis.

    Prophase: Mitosis begins with the condensing of the chromatin to form chromosomes in the phase called prophase. Two copies of each chromosome exist; each one is a chromatid. Two chromatids are joined to one another at a region called the centromere. As prophase unfolds, the chromatids become visible in pairs (called sister chromatids), the spindle fibers form, the nucleoli disappear, and the nuclear envelope dissolves.

    In animal cells during prophase, microscopic bodies called centrioles begin to migrate to opposite sides of the cell. When the centrioles reach the poles of the cell, they produce and are then surrounded by a series of radiating microtubules called an aster. Centrioles and asters are not present in most plant or fungal cells.

    As prophase continues, the chromatids attach to spindle fibers that extend out from opposite poles of the cell. The spindle fibers attach at the region of the centromere at a structure called the kinetochore, an area of protein in the centromere region. Eventually, all pairs of chromatids reach the center of the cell, a region called the equatorial plate.

    Metaphase: Metaphase is the stage of mitosis in which the pairs of chromatids line up on the equatorial plate. This region is also called the metaphase plate. In a human cell, 92 chromosomes in 46 pairs align at the equatorial plate. Each pair is connected at the centromere, where the spindle fiber is attached (more specifically at the kinetochore).

    Anaphase: At the beginning of anaphase, the sister chromatids move apart from one another. The chromatids are called chromosomes after the separation. Each chromosome is attached to a spindle fiber, and the members of each chromosome pair are drawn to opposite poles of the cell by the spindle fibers. During anaphase, the chromosomes can be seen moving. They take on a rough V shape because of their midregion attachment to the spindle fibers. The movement toward the poles is accomplished by several mechanisms, such as an elongation of the spindle fibers, which results in pushing the poles apart.

    The result of anaphase is an equal separation and distribution of the chromosomes. In human cells, a total of 46 chromosomes move to each pole as the process of mitosis continues.

    Telophase: In telophase, the chromosomes finally arrive at the opposite poles of the cell. The distinct chromosomes begin to fade from sight as masses of chromatin are formed again. The events of telophase are essentially the reverse of those in prophase. The spindle is dismantled and its amino acids are recycled, the nucleoli reappear, and the nuclear envelope is reformed.

    Cytokinesis: Cytokinesis is the process in which the cytoplasm divides and two separate cells form. Note that cytokinesis is separate from the four stages of mitosis. In animal cells, cytokinesis begins with the formation of a cleavage furrow in the center of the cell. With the formation of the furrow, the cell membrane begins to pinch into the cytoplasm, and the formation of two cells begins. This process is often referred to as cell cleavage. Microfilaments contract during cleavage and assist the division of the cell into two daughter cells.

    In plant cells, cytokinesis occurs by a different process because a rigid cell wall is involved. Cleavage does not take place in plant cells. Rather, a new cell wall is assembled at the center of the cell, beginning with vesicles formed from the Golgi apparatus (see Bilogy of Cells). As the vesicles join, they form a double membrane called the cell plate. The cell plate forms in the middle of the cytoplasm and grows outward to fuse with the cell membrane. The cell plate separates the two daughter cells. As cell wall material is laid down, the two cells move apart from one another to yield two new daughter cells.

    Mitosis serves several functions in living cells. In many simple organisms, it is the method for asexual reproduction (for example, in the cells of a fungus). In multicellular organisms, mitosis allows the entire organism to grow by forming new cells and replacing older cells. In certain species, mitosis is used to heal wounds or regenerate body parts. It is the universal process for cell division in eukaryotic cells.

    Cell Nucleus

    A distinguishing feature of a living thing is that it reproduces independent of other living things. This reproduction occurs at the cellular level. In certain parts of the body, such as along the gastrointestinal tract, the cells reproduce often. In other parts of the body, such as in the nervous system, the cells reproduce less frequently. With the exception of only a few kinds of cells, such as red blood cells (which lack nuclei when fully mature), all cells of the human body reproduce.

    In eukaryotic cells (see Bilogy of Cells), the structure and contents of the nucleus are of fundamental importance to an understanding of cell reproduction. The nucleus contains the hereditary material (DNA) of the cell assembled into chromosomes. In addition, the nucleus usually contains one or more prominent nucleoli (dense bodies that are the site of ribosome synthesis).

    Anatomy of the Nucleus

    Figure 2: Anatomy of the Nucleus

    The nucleus is surrounded by a nuclear envelope consisting of a double membrane that is continuous with the endoplasmic reticulum. Transport of molecules between the nucleus and cytoplasm is accomplished through a series of nuclear pores lined with proteins that facilitate the passage of molecules out of the nucleus. The proteins provide a certain measure of selectivity in the passage of molecules across the nuclear membrane.

    The nuclear material consists of deoxyribonucleic acid (DNA) organized into long strands. The strands of DNA are composed of nucleotides bonded to one another by covalent bonds. DNA molecules are extremely long relative to the cell; there are approximately 6 feet of DNA in a single human cell. However, in the chromosome, the DNA is condensed and packaged with protein into manageable bodies. The mass of DNA material and its associated protein is chromatin.

    To form chromatin, the DNA molecule is wound around globules of a protein called histone. The units formed in this way are nucleosomes. Millions of nucleosomes are connected by short stretches of histone protein, much like beads on a string. The configuration of the nucleosomes in a coil causes additional coiling of the DNA and the eventual formation of the chromosome.

  • Cellular Respiration

    What is Cellular Respiration?

    Some organisms, such as plants, can trap the energy in sunlight through photosynthesis (see Photosynthesis) and store it in the chemical bonds of carbohydrate molecules. The principal carbohydrate formed through photosynthesis is glucose. Other types of organisms, such as animals, fungi, many protozoa, and a large portion of bacteria, are unable to perform this process. Therefore, these organisms must rely on the carbohydrates formed in plants to obtain the energy necessary for their metabolic processes.

    Animals and other organisms obtain the energy available in carbohydrates through the process of cellular respiration. Cells take the carbohydrates into their cytoplasm, and through a complex series of metabolic processes, they break down the carbohydrates and release the energy. The energy is generally not needed immediately; rather, it is used to combine adenosine diphosphate (ADP) with phosphate ions to form adenosine triphosphate (ATP) molecules. The ATP can then be used for processes in the cells that require energy, much as a battery powers a mechanical device.

    During the process of cellular respiration, carbon dioxide is given off. This carbon dioxide can be used by plant cells during photosynthesis to form new carbohydrates. Also in the process of cellular respiration, oxygen gas is required to serve as an acceptor of electrons. This oxygen is identical to the oxygen gas given off during photosynthesis. Thus, there is an interrelationship between the processes of photosynthesis and cellular respiration, namely the entrapment of energy available in sunlight and the provision of the energy for cellular processes in the form of ATP.

    The overall mechanism of cellular respiration involves four processes: glycolysis, in which glucose molecules are broken down to form pyruvic acid molecules; the Krebs cycle, in which pyruvic acid is further broken down and the energy in its molecule is used to form high-energy compounds, such as nicotinamide adenine dinucleotide (NADH); the electron transport system, in which electrons are transported along a series of coenzymes and cytochromes and the energy in the electrons is released; and chemiosmosis, in which the energy given off by electrons pumps protons across a membrane and provides the energy for ATP synthesis. The general chemical equation for cellular respiration is:

    C6H12O6 + 6 O2 → 6 H2O + 6CO2 + energy

    Figure 1. provides an overview of cellular respiration. Glucose is converted to pyruvic acid in the cytoplasm, which is then used to produce acetyl CoA in the mitochondrion. Finally, the Krebs cycle proceeds in the mitochondrion. Electron transport and chemiosmosis result in energy release; ATP synthesis also occurs in the mitochondrion.

    Glycolysis

    Glycolysis is the process in which one glucose molecule is broken down to form two molecules of pyruvic acid (also called pyruvate). The glycolysis process is a multi-step metabolic pathway that occurs in the cytoplasm of animal cells, plant cells, and the cells of microorganisms. At least six enzymes operate in the metabolic pathway.

    In the first and third steps of the pathway, ATP energizes the molecules. Thus, two ATP molecules must be expended in the process. Further along in the process, the six-carbon glucose molecule converts into intermediary compounds and is then split into two three-carbon compounds. The latter undergo additional conversions and eventually form pyruvic acid at the conclusion of the process.

    During the latter stages of glycolysis, four ATP molecules are synthesized using the energy given off during the chemical reactions. Thus, four ATP molecules are synthesized and two ATP molecules are used during glycolysis, for a net gain of two ATP molecules.

    An overview of cellular respiration

    Figure 1. An overview of cellular respiration.

    Another reaction during glycolysis yields enough energy to convert NAD to NADH (plus a hydrogen ion). The reduced coenzyme (NADH) will later be used in the electron transport system, and its energy will be released. During glycolysis, two NADH molecules are produced.

    Because glycolysis does not require oxygen, the process is considered to be anaerobic. For certain anaerobic organisms, such as some bacteria and fermentation yeasts, glycolysis is the sole source of energy.

    Glycolysis is a somewhat inefficient process because much of the cellular energy remains in the two molecules of pyruvic acid that are created. Interestingly, this process is somewhat similar to a reversal of photosynthesis (see Photosynthesis).

    Krebs Cycle

    Following glycolysis, the mechanism of cellular respiration involves another multi-step process—the Krebs cycle, which is also called the citric acid cycle or the tricarboxylic acid cycle. The Krebs cycle uses the two molecules of pyruvic acid formed in glycolysis and yields high-energy molecules of NADH and Flavin adenine dinucleotide (FADH2), as well as some ATP.

    Krebs Cycle
    Krebs Cycle

    The Krebs cycle occurs in the mitochondrion of a cell (see Figure 6). This sausage-shaped organelle possesses inner and outer membranes and, therefore, inner and outer compartments. The inner membrane is folded over itself many times; the folds are called cristae. They are somewhat similar to the thylakoid membranes in chloroplasts (see Photosynthesis). Located along the cristae are the important enzymes necessary for the proton pump and for ATP production.

    Prior to entering the Krebs cycle, the pyruvic acid molecules are altered. Each three-carbon pyruvic acid molecule undergoes conversion to a substance called acetyl-coenzyme A, or Acetyl-CoA. During the process, the pyruvic acid molecule is broken down by an enzyme, one carbon atom is released in the form of carbon dioxide, and the remaining two carbon atoms are combined with a coenzyme called coenzyme A. This combination forms Acetyl-CoA. In the process, electrons and a hydrogen ion are transferred to NAD to form high-energy NADH.

    Acetyl-CoA enters the Krebs cycle by combining with a four-carbon acid called oxaloacetic acid. The combination forms the six-carbon acid called citric acid. Citric acid undergoes a series of enzyme-catalyzed conversions. The conversions, which involve up to ten chemical reactions, are all brought about by enzymes. In many of the steps, high-energy electrons are released to NAD. The NAD molecule also acquires a hydrogen ion and becomes NADH. In one of the steps, FAD serves as the electron acceptor, and it acquires two hydrogen ions to become FADH2. Also, in one of the reactions, enough energy is released to synthesize a molecule of ATP. Because for each glucose molecule there are two pyruvic acid molecules entering the system, two ATP molecules are formed.

    Also during the Krebs cycle, the two carbon atoms of Acetyl-CoA are released, and each forms a carbon dioxide molecule. Thus, for each Acetyl-CoA entering the cycle, two carbon dioxide molecules are formed. Two Acetyl-CoA molecules enter the cycle, and each has two carbon atoms, so four carbon dioxide molecules will form. Add these four molecules to the two carbon dioxide molecules formed in the conversion of pyruvic acid to Acetyl-CoA, and it adds up to six carbon dioxide molecules. These six CO2 molecules are given off as waste gas in the Krebs cycle. They represent the six carbons of glucose that originally entered the process of glycolysis.

    At the end of the Krebs cycle, the final product is oxaloacetic acid. This is identical to the oxaloacetic acid that begins the cycle. Now the molecule is ready to accept another Acetyl-CoA molecule to begin another turn of the cycle. All told, the Krebs cycle forms (per two molecules of pyruvic acid) two ATP molecules, ten NADH molecules, and two FADH2 molecules. The NADH and the FADH2 will be used in the electron transport system.

    Electron Transport System

    The electron transport system occurs in the cristae of the mitochondria, where a series of cytochromes (enzymes) and coenzymes exist. These cytochromes and coenzymes act as carrier molecules and transfer molecules. They accept high-energy electrons and pass the electrons to the next molecule in the system. At key proton-pumping sites, the energy of the electrons transports protons across the membrane into the outer compartment of the mitochondrion.

    Each NADH molecule is highly energetic, which accounts for the transfer of six protons into the outer compartment of the mitochondrion. Each FADH2 molecule accounts for the transfer of four protons. The flow of electrons is similar to that taking place in photosynthesis. Electrons pass from NAD to FAD, to other cytochromes and coenzymes, and eventually they lose much of their energy. In cellular respiration, the final electron acceptor is an oxygen atom. In their energy-depleted condition, the electrons unite with an oxygen atom. The electron-oxygen combination then reacts with two hydrogen ions (protons) to form a water molecule (H2O).

    The role of oxygen in cellular respiration is substantial. As a final electron acceptor, it is responsible for removing electrons from the electron transport system. If oxygen were not available, electrons could not be passed among the coenzymes, the energy in electrons could not be released, the proton pump could not be established, and ATP could not be produced. In humans, breathing is the essential process that brings oxygen into the body for delivery to the cells to participate in cellular respiration.

    Chemiosmosis

    The actual production of ATP in cellular respiration takes place through the process of chemiosmosis (see Cells and Energy). Chemiosmosis involves the pumping of protons through special channels in the membranes of mitochondria from the inner to the outer compartment. The pumping establishes a proton (H+) gradient. After the gradient is established, protons diffuse down the gradient through a transport protein called ATP synthase. The flow of hydrogens catalyzes the pairing of a phosphate with ADP, forming ATP.

    The energy production of cellular respiration is substantial. Most biochemists agree that 36 molecules of ATP can be produced for each glucose molecule during cellular respiration as a result of the Krebs cycle reactions, the electron transport system, and chemiosmosis. Also, two ATP molecules are produced through glycolysis, so the net yield is 38 molecules of ATP. These ATP molecules may then be used in the cell for its needs. However, the ATP molecules cannot be stored for long periods of time, so cellular respiration must constantly continue in order to regenerate the ATP molecules as they are used. Each ATP molecule is capable of releasing 7.3 kilocalories of energy per mole.

    Fermentation

    Fermentation is an anaerobic process in which energy can be released from glucose even though oxygen is not available. Fermentation occurs in yeast cells, and a form of fermentation takes place in bacteria and in the muscle cells of animals.

    In yeast cells (the yeast used for baking bread and producing alcoholic beverages), glucose can be metabolized through cellular respiration as in other cells. When oxygen is lacking, however, glucose is still metabolized to pyruvic acid via glycolysis. The pyruvic acid is converted first to acetaldehyde and then to ethyl alcohol. The net gain of ATP to the yeast cell is two molecules—the two molecules of ATP normally produced in glycolysis.

    Yeasts are able to participate in fermentation because they have the necessary enzyme to convert pyruvic acid to ethyl alcohol. This process is essential because it removes electrons and hydrogen ions from NADH during glycolysis. The effect is to free the NAD so it can participate in future reactions of glycolysis. The net gain to the yeast cell of two ATP molecules permits it to remain alive for some time. However, when the percentage of ethyl alcohol reaches approximately 15 percent, the alcohol kills the yeast cells.

    Yeast is used in both bread and alcohol production. Alcohol fermentation is the process that yields beer, wine, and other spirits. The carbon dioxide given off during fermentation supplements the carbon dioxide given off during the Krebs cycle and causes bread to rise.

    In muscle cells, another form of fermentation takes place. When muscle cells contract too frequently (as in strenuous exercise), they rapidly use up their oxygen supply. As a result, the electron transport system and Krebs cycle slow considerably, and ATP production is slowed. However, muscle cells have the ability to produce a small amount of ATP through glycolysis in the absence of oxygen. The muscle cells convert glucose to pyruvic acid. An enzyme in the muscle cells then converts the pyruvic acid to lactic acid. As in the yeast, this reaction frees up the NAD while providing the cells with two ATP molecules from glycolysis. Eventually, however, the lactic acid buildup causes intense fatigue, and the muscle stops contracting.

  • Photosynthesis

    What is Photosynthesis?

    A great variety of living things on Earth, including all green plants, synthesize their foods from simple molecules, such as carbon dioxide and water. For this process, the organisms require energy, and that energy is derived from sunlight.

    Figure 1. shows the energy relationships in living cells. Light energy is captured in the chloroplast of plant cells and used to synthesize glucose molecules, shown as C6H12O6. In the process, oxygen (O2) is released as a waste product. The glucose and oxygen are then used in the mitochondrion of the plant cell, and the energy is released and used to fuel the synthesis of ATP from ADP and P. In the reaction, CO2 and water are released in the mitochondrion to be reused in photosynthesis in the chloroplast.

    Energy relationships in living cells Cycles
    Energy relationships in living cells Cycles

    Energy relationships in living cells

    Figure 1. Energy relationships in living cells.

    The process of utilizing energy to synthesize carbohydrate molecules is called photosynthesis. Photosynthesis is actually two separate processes. in the first process, energy-rich electrons flow through a series of coenzymes and other molecules. This electron energy is trapped. During the trapping process, adenosine triphosphate (ATP) molecules and molecules of nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) are formed. Both ATP and NADPH are rich in energy. These molecules are used in the second process, where carbon dioxide molecules are bound into carbohydrates too form organic substances such as glucose.

    Chloroplast

    The organelle in which photosynthesis occurs (in the leaves and green stems of plants, for example) is called the chloroplast. Chloroplasts are relatively large organelles, containing a watery, protein-rich fluid called stroma. The stroma contains many small structures composed of membranes that resemble stacks of coins. Each stack is a granum (the plural form is grana). Each membrane in the stack is a thylakoid. Within the thylakoid membranes of the granum, many of the reactions of photosynthesis take place. The thylakoids are somewhat similar to the cristae of mitochondria (see Cellular Respiration).

    Photosystems

    Pigment molecules organized into photosystems capture sunlight in the chloroplast. Photosystems are clusters of light-absorbing pigments with some associated molecules—proton (hydrogen ion) pumps, enzymes, coenzymes, and cytochromes (see Cells and Energy). Each photosystem contains about 200 molecules of a green pigment called chlorophyll and about 50 molecules of another family of pigments called carotenoids. In the reaction center of the photosystem, the energy of sunlight is converted to chemical energy. The center is sometimes called a light-harvesting antenna.

    There are two photosystems within the thylakoid membranes, designated photosystem I and photosystem II. The reaction centers of these photosystems are P700 and P680, respectively. The energy captured in these reaction centers drives chemiosmosis, and the energy of chemiosmosis stimulates ATP production in the chloroplasts.

    Process of Photosynthesis

    The process of photosynthesis is conveniently divided into two parts: the energy-fixing reaction (also called the light reaction) and the carbon-fixing reaction (also called the light-independent reaction or the dark reaction).

    Energy-fixing reaction

    The energy-fixing reaction of photosynthesis begins when light is absorbed in photosystem II in the thylakoid membranes. The energy of the sunlight, captured in the P680 reaction center, causes the electrons from P680’s chlorophyll to move to a higher, unstable energy level. These electrons pass through a series of cytochromes in the nearby electron-transport system.

    After passing through the electron transport system, the energy-rich electrons eventually enter Photosystem-I. Some of the energy of the electron is used to pump protons across the thylakoid membrane, and this pumping sets up the potential for chemiosmosis.

    The spent electrons from P680 enter the P700 reaction center in photosystem I. Sunlight activates the electrons, which receive a second boost out of the chlorophyll molecules. There they reach a high energy level. The electrons progress through a second electron transport system, but this time there is no proton pumping. Rather, the energy reduces NADP. This reduction occurs as two electrons join NADP and energize the molecule. Because NADP acquires two negatively charged electrons, it attracts two positively charged protons to balance the charges. Consequently, the NADP molecule is reduced to NADPH, a molecule that contains much energy.

    Because electrons have flowed out of the P680 reaction center, the chlorophyll molecules are left without a certain number of electrons. Electrons secured from water molecules replace these electrons. Each split water molecule releases two electrons that enter the chlorophyll molecules to replace those lost. The split water molecules also release two protons that enter the cytoplasm near the thylakoid and are available to increase the chemiosmotic gradient.

    The third product of the split water molecules is oxygen. Two oxygen atoms combine with one another to form molecular oxygen (O2), which is given off as the by-product of photosynthesis; it fills the atmosphere and is used by all oxygen-requiring organisms, including plant and animal cells.

    Described above are the noncyclic energy-fixing reactions (see Figure 2). Certain plants and autotrophic prokaryotes are also known to participate in cyclic energy-fixing reactions. These reactions involve only photosystem I and the P700 reaction center. Excited electrons leave the reaction center, pass through coenzymes of the electron transport system, and follow a special pathway back to P700. Each electron powers the proton pump and encourages the transport of a proton across the thylakoid membrane. This process enriches the proton gradient and eventually leads to the generation of ATP.

    The energy-fixing reactions of photosynthesis

    Figure 2. The energy-fixing reactions of photosynthesis.

    ATP production in the energy-fixing reactions of photosynthesis occurs by the process of chemiosmosis (explained in Cells and Energy). Essentially, this process consists of a rush of protons across a membrane (the thylakoid membrane, in this case), accompanied by the synthesis of ATP molecules. Biochemists have calculated that the proton concentration on one side of the thylakoid is 10,000 times that of the opposite side of the membrane.

    In photosynthesis, the protons pass back across the membranes through channels lying alongside sites where enzymes are located. As the protons pass through the channels, the energy of the protons is released to form high-energy ATP bonds. ATP is formed in the energy-fixing reactions along with the NADPH formed in the main reactions. Both ATP and NADPH provide the energy necessary for the synthesis of carbohydrates that occurs in the second major set of events in photosynthesis.

    Carbon-fixing reaction

    Glucose and other carbohydrates are synthesized in the carbon-fixing reaction of photosynthesis, often called the Calvin cycle after Melvin Calvin, who performed much of the biochemical research (see Figure 3). This phase of photosynthesis occurs in the stroma of the plant cell.

    A carbon-fixing reaction or the Calvin cycle
    A carbon-fixing reaction or the Calvin cycle

    Figure 3. A carbon-fixing reaction, also called the Calvin cycle.

    In the carbon-fixing reaction, an essential material is carbon dioxide, which is obtained from the atmosphere. The carbon dioxide is attached to a five-carbon compound called ribulose bisphosphate. Ribulose bisphosphate carboxylase catalyzes this reaction.

    After carbon dioxide has been joined to ribulose bisphosphate, a six-carbon product forms, which immediately breaks into two three-carbon molecules called phosphoglycerate. Each phosphoglycerate molecule converts to another organic compound, but only in the presence of ATP. The ATP used is the ATP synthesized in the energy-fixing reaction. The organic compound formed converts to still another organic compound using the energy present in NADPH. Again, the energy-fixing reaction provides the essential energy. Each of the organic compounds that results consists of three carbon atoms. Eventually, the compounds interact with one another and join to form a single molecule of six-carbon glucose. This process also generates additional molecules of ribulose bisphosphate to participate in further carbon-fixing reactions.

    Glucose can be stored in plants in several ways. In some plants, the glucose molecules are joined to one another to form starch molecules. Potato plants, for example, store starch in tubers (underground stems). In some plants, glucose converts to fructose (fruit sugar), and the energy is stored in this form. In still other plants, fructose combines with glucose to form sucrose, commonly known as table sugar. The energy is stored in carbohydrates in this form. Plant cells obtain energy for their activities from these molecules. Animals use the same forms of glucose by consuming plants and delivering the molecules to their cells.

    All living things on Earth depend in some way on photosynthesis. It is the main mechanism for bringing the energy of sunlight into living systems and making that energy available for the chemical reactions taking place in cells.

  • Cells and Energy

    What are Cells and Energy?

    The Laws of Thermodynamics; Life can exist only where molecules and cells remain organized. All cells need energys to maintain organization. Physicists define energy as the ability to do work; in this case, the work is the continuation of life itself.

    Energy has been expressed in terms of reliable observations known as the laws of thermodynamics. There are two such laws. The first law of thermodynamics states that energy can neither be created nor destroyed. This law implies that the total amount of energy in a closed system (for example, the universe) remains constant. Energys neither enters nor leaves a closed system.

    Cells and Energy 1

    Within a closed system, energy can change, however. For instance, the chemical energy in gasoline is released when the fuel combines with oxygen and a spark ignites the mixture within a car’s engine. The gasoline’s chemical energy is changed into heat energy, sound energy, and the energy of motion.

    The second law of thermodynamics states that the amount of available energy in a closed system is decreasing constantly. Energy becomes unavailable for use by living things because of entropy, which is the degree of disorder or randomness of a system. The entropy of any closed system is constantly increasing. In essence, any closed system tends toward disorganization.

    Unfortunately, the transfers of energy in living systems are never completely efficient. Every body movement, every thought, and every chemical reaction in the cells involves a shift of energy and a measurable decrease of energy available to do work in the process. For this reason, considerably more energy must be taken into the system than is necessary to carry out the actions of life.

    Chemical Reactions

    Most chemical compounds do not combine with one another automatically, nor do chemical compounds break apart automatically. The great majority of the chemical reactions that occur within living things must be energized. This means that the atoms of a molecule must be separated by energy put into the system. The energy forces apart the atoms in the molecules and allows the reaction to take place.

    To initiate a chemical reaction, a type of “spark,” referred to as the energy of activation, is needed. For example, hydrogen and oxygen can combine to form water at room temperature, but the reaction requires activation energy.

    Any chemical reaction in which energy is released is called an exergonic reaction. In an exergonic chemical reaction, the products end up with less energy than the reactants. Other chemical reactions are endergonic reactions. In endergonic reactions, energy is obtained and trapped from the environment. The products of endergonic reactions have more energy than the reactants taking part in the chemical reaction. For example, plants carry out the process of photosynthesis, in which they trap energy from the sun to form carbohydrates (see Photosynthesis).

    The activation energy needed to spark an exergonic or endergonic reaction can be heat energy or chemical energy. Reactions that require activation energy can also proceed in the presence of biological catalysts. Catalysts are substances that speed up chemical reactions but remain unchanged themselves. Catalysts work by lowering the required amount of activation energy for the chemical reaction. For example, hydrogen and oxygen combine with one another in the presence of platinum. In this case, platinum is the catalyst. In biological systems, the most common catalysts are protein molecules called enzymes. Enzymes are absolutely essential if chemical reactions are to occur in cells.

    Enzymes

    The chemical reactions in all cells of living things operate in the presence of biological catalysts called enzymes. Because a particular enzyme catalyzes only one reaction, there are thousands of different enzymes in a cell catalyzing thousands of different chemical reactions. The substance changed or acted on by an enzyme is its substrate. The products of a chemical reaction catalyzed by an enzyme are end products.

    All enzymes are composed of proteins. (Proteins are chains of amino acids; see The Chemical Basis of Life.) When an enzyme functions, a key portion of the enzyme, called the active site, interacts with the substrate. The active site closely matches the molecular configuration of the substrate. After this interaction has taken place, a change in shape in the active site places a physical stress on the substrate. This physical stress aids the alteration of the substrate and produces the end products. During the time the active site is associated with the substrate, the combination is referred to as the enzyme-substrate complex. After the enzyme has performed its work, the product or products are released from the enzyme’s active site. The enzyme is then free to function in another chemical reaction.

    Enzyme-catalyzed reactions occur extremely fast. They happen about a million times faster than uncatalyzed reactions. With some exceptions, the names of enzymes end in “–ase.” For example, the enzyme that breaks down hydrogen peroxide to water and hydrogen is catalase. Other enzymes include amylase, hydrolase, peptidase, and kinase.

    The rate of an enzyme-catalyzed reaction depends on a number of factors, such as the concentration of the substrate, the acidity and temperature of the environment, and the presence of other chemicals. At higher temperatures, enzyme reactions occur more rapidly, but only up to a point. Because enzymes are proteins, excessive amounts of heat can change their structures, rendering them inactive. An enzyme altered by heat is said to be denatured.

    Enzymes work together in metabolic pathways. A metabolic pathway is a sequence of chemical reactions occurring in a cell. A single enzyme-catalyzed reaction may be one of multiple reactions in a metabolic pathway. Metabolic pathways may be of two general types: catabolic and anabolic. Catabolic pathways involve the breakdown or digestion of large, complex molecules. The general term for this process is catabolism. Anabolic pathways involve the synthesis of large molecules, generally by joining smaller molecules together. The general term for this process is anabolism.

    Many enzymes are assisted by chemical substances called cofactors. Cofactors may be ions or molecules associated with an enzyme and are required in order for a chemical reaction to take place. Ions that might operate as cofactors include those of iron, manganese, and zinc. Organic molecules acting as cofactors are referred to as coenzymes.

    Adenosine Triphosphate (ATP)

    Adenosine Triphosphate (ATP)

    The chemical substance that serves as the currency of energy in a cell is adenosine triphosphate (ATP). ATP is referred to as currency because it can be “spent” in order to make chemical reactions occur. The more energy required for a chemical reaction, the more ATP molecules must be spent.

    Virtually all forms of life use ATP, a nearly universal molecule of energy transfer. The energy released during catabolic reactions is stored in ATP molecules. In addition, the energy trapped in anabolic reactions (such as photosynthesis) is trapped in ATP molecules.

    An ATP molecule consists of three parts. One part is a double ring of carbon and nitrogen atoms called adenine. Attached to the adenine molecule is a small five-carbon carbohydrate called ribose. Attached to the ribose molecule are three phosphate units linked together by covalent bonds.

    Adenosine Triphosphate Structure
    Adenosine Triphosphate Structure

    The covalent bonds that unite the phosphate units in ATP are high-energy bonds. When an ATP molecule is broken down by an enzyme, the third (terminal) phosphate unit is released as a phosphate group, which is an ion. When this happens, approximately 7.3 kilocalories of energy are released. (A kilocalorie equals 1,000 calories.) This energy is made available to do the work of the cell.

    The adenosine triphosphatase enzyme accomplishes the breakdown of an ATP molecule. The products of ATP breakdown are adenosine diphosphate (ADP) and a phosphate ion. Adenosine diphosphate and the phosphate ion can be reconstituted to form ATP, much like a battery can be recharged. To accomplish this, synthesis energy must be available. This energy can be made available in the cell through two extremely important processes: photosynthesis.

    ATP Production

    ATP is generated from ADP and phosphate ions by a complex set of processes occurring in the cell. These processes depend on the activities of a special group of coenzymes. Three important coenzymes are nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide phosphate (NADP), and Flavin adenine dinucleotide (FAD).

    NAD and NADP are structurally similar to ATP. Both molecules have a nitrogen-containing ring called nicotinic acid, which is the chemically active part of the coenzymes. In FAD, the chemically active portion is the Flavin group. The vitamin riboflavin is used in the body to produce this Flavin group.

    All coenzymes perform essentially the same work. During the chemical reactions of metabolism, coenzymes accept electrons and pass them on to other coenzymes or other molecules. The removal of electrons or protons from a coenzyme is oxidation. The addition of electrons to a molecule is reduction. Therefore, the chemical reactions performed by coenzymes are called oxidation-reduction reactions.

    The oxidation-reduction reactions performed by the coenzymes and other molecules are essential to the energy metabolism of the cell. Other molecules participating in this energy reaction are called cytochromes. Together with the coenzymes, cytochromes accept and release electrons in a system called the electron transport system. The passage of energy-rich electrons among cytochromes and coenzymes drains the energy from the electrons to form ATP from ADP and phosphate ions.

    The actual formation of ATP molecules requires a complex process called chemiosmosis. Chemiosmosis involves the creation of a steep proton (hydrogen ion) gradient. This gradient occurs between the membrane-bound compartments of the mitochondria of all cells and the chloroplasts of plant cells. A gradient is formed when large numbers of protons (hydrogen ions) are pumped into the membrane-bound compartments of the mitochondria. The protons build up dramatically within the compartment, finally reaching an enormous number. The energy released from the electrons during the electron transport system pumps the protons.

    After large numbers of protons have gathered within the compartments of mitochondria and chloroplasts, they suddenly reverse their directions and escape back across the membranes and out of the compartments. The escaping protons release their energy in this motion. This energy is used by enzymes to unite ADP with phosphate ions to form ATP. The energy is trapped in the high-energy bond of ATP by this process, and the ATP molecules are made available to perform cell work. The movement of protons is chemiosmosis because it is a movement of chemicals (in this case, protons) across a semipermeable membrane. Because chemiosmosis occurs in mitochondria and chloroplasts, these organelles play an essential role in the cell’s energy metabolism. Photosynthesis explains how energy is trapped in the chloroplasts in plants, while Cellular Respiration explains how energy is released in the mitochondria of plant and animal cells.