Tag: Definition

Definition!

What is a Definition? It is a statement of the meaning of a term (a word, phrase, or other set of symbols). As well as, Descriptions can classify into two large categories, intentional purposes (which try to give the essence of a term) and extensional purposes (which proceed by listing the objects that a term describes).

Another important category of definitions is the class of ostensive illustrations, which convey the meaning of a term by pointing out examples. Also, A term may have many different senses and multiple meanings and thus require multiple reports.

  • A statement of the meaning of a word or word group or a sign or symbol dictionary definitions. The statement expresses the essential nature of something, a product of defining.
  • The action or process of stating the meaning of a word or word group.

  • DNA (Deoxyribonucleic Acid)

    DNA (Deoxyribonucleic Acid)

    Deoxyribonucleic Acid (DNA) is a molecule that carries the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. DNA and RNA are nucleic acids; alongside proteins, lipids and complex carbohydrates (polysaccharides), they are one of the four major types of macromolecules that are essential for all known forms of life. Most DNA molecules consist of two biopolymer strands coiled around each other to form a double helix. DNA Structure, History of DNA Research.

    What is DNA?

    We all know that elephants only give birth to little elephants, giraffes to giraffes, dogs to dogs and so on for every type of living creature. But why is this so? The answer lies in a molecule called deoxyribonucleic acid (DNA), which contains the biological instructions that make each species unique. DNA, along with the instructions it contains, is passed from adult organisms to their offspring during reproduction. History of DNA Research.

    What is meaning of DNA?

    DNA stands for deoxyribonucleic acid, sometimes called “the molecule of life,” as almost all organisms have their genetic material codified as DNA. Since each person’s DNA is unique, “DNA typing” is a valuable tool in connecting suspects to crime scenes. You can also use the word less scientifically, as in “it’s just not in my DNA to sit through six hours of meetings.”

    You got your DNA from your parents, we call it ‘hereditary material’ (information that is passed on to the next generation). Nobody else in the world will have DNA the same as you, unless you have an identical twin. Deoxyribonucleic acid is a large molecule in the shape of a double helix. That’s a bit like a ladder that’s been twisted many times.

    The two DNA strands are termed polynucleotides since they are composed of simpler monomer units called nucleotides. Each nucleotide is composed of one of four nitrogen-containing nucleobases either cytosine (C), guanine (G), adenine (A), or thymine (T) and a sugar called deoxyribose and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. The nitrogenous bases of the two separate polynucleotide strands are bound together (according to base pairing rules (A with T, and C with G) with hydrogen bonds to make double-stranded DNA. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 trillion tons of carbon (TTC).

    DNA stores biological information. The DNA backbone is resistant to cleavage, and both strands of the double-stranded structure store the same biological information. This information is replicated as and when the two strands separate. A large part of DNA (more than 98% for humans) is non-coding, meaning that these sections do not serve as patterns for protein sequences.

    The two strands of DNA run in opposite directions to each other and are thus anti-parallel. Attached to each sugar is one of four types of nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes biological information. RNA strands are created using DNA strands as a template in a process called transcription. Under the genetic code, these RNA strands are translated to specify the sequence of amino acids within proteins in a process called translation.

    Within eukaryotic cells, DNA is organized into long structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the eukaryotic chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.

    DNA was first isolated by Friedrich Miescher in 1869. Its molecular structure was identified by James Watson and Francis Crick in 1953, whose model-building efforts were guided by X-ray diffraction data acquired by Raymond Gosling who was a post-graduate student of Rosalind Franklin. DNA is used by researchers as a molecular tool to explore physical laws and theories, such as the ergodic theorem and the theory of elasticity. The unique material properties of DNA have made it an attractive molecule for material scientists and engineers interested in micro- and nano-fabrication. Among notable advances in this field are DNA origami and DNA-based hybrid materials. And also read it DNA Structure, History of DNA Research.

  • What is Master the Art of Scheduling?

    What is Master the Art of Scheduling?

    “Where are you on the schedule?” Develop the ability to predict the amount of time as a sequence of key tasks that a project should take. And yet we all work with software developers who hate the pressure of committing to a schedule because to complete work usually takes “as long as it takes.” But you can’t effectively run a business without the confidence to work toward a schedule.

    When you recognize the value of time management skills, you become the overseer of your life, with your schedule as your command center. Many people think that creating a schedule is as easy as jotting down the time and activity on a piece of paper. However, scheduling is so much more than that.

    A well-planned schedule of everyday tasks is more than just a reminder of what needs to be done. It also allows you to make time for important tasks that are in line with your goals. It makes you become aware of how you spend your time each day. It helps you to recognize areas that need adjustments so that you can achieve balance between your personal life and your profession. So how should you schedule your time each day? What are the tools you need to become a “master scheduler?” Here are the strategies to learn:

    Gather Your Scheduling Tools

    In general, you would need three essential scheduling tools, and these are:

    A daily planner,

    A weekly planner, and

    A monthly planner

    The daily planner helps to keep you on the right track each day. It enables you to concentrate on exactly what tasks need to be done and how much time you have for each.

    The weekly planner serves as your overview of the events planned out for that week as well as the tasks that you need to accomplish. It helps you get to see what is ahead of you, because focusing only on the everyday tasks might cause you to forget about what is in store for tomorrow, or the day after that.

    Now, you might think that you do not need a monthly planner if you have a weekly one. However, it always helps to have all the dates of the month laid out on a single page. This will enable you to see the important dates of that month and plan your week and days around them.

    However, it is possible to keep a monthly planner without the weekly planner. Just make sure that there is enough space for you to jot down your weekly tasks on the monthly planner.

    There are plenty of planners whether digital or printed out there, so choose your layout carefully. Most of the time, you will find that many planners already have daily, weekly, and monthly sections. This is helpful, especially if you want to carry your planner around. Take care not to purchase more than one type of planner, because you would only end up feeling confused as to which one you should write your next set of tasks.

    One suggestion on how to organize your different planners is that you should have a portable daily planner, and a desktop or wall-mounted weekly and/or monthly planner. This is because you will likely need to check your daily planner constantly throughout the day, while you only need to jot things down and review your weekly/monthly planner once a week. A large monthly planner is helpful as well, because you will want to see everything at a single glance.

    Once you have your scheduling tools, the next step is to create a scheduling routine.

    Create a Scheduling Routine

    Do you take time at the end of each day to plan for the following day? If you do not, then now is the best time to build this habit. A master scheduler should set aside a time each day to plan for tomorrow, each week for the week ahead, and each month to review everything and plan for the next month.

    In most cases, it will only take ten to twenty minutes to plan for the following day and thirty minutes to plan for the week and month ahead. However, the time you would invest in planning will save you from many problems in the future.

    After you have set a fixed “scheduling” time, you should then establish a routine on how to schedule your time. Here are the recommended steps:

    1. Time-block non-negotiable appointments

    Certain parts of the day may be out of your control; such as board meetings or dentist appointments. You should secure them all first, otherwise you might end up with overlapping appointments.

    It must be emphasized that you should also time-block the hours when you will be sleeping. Have to establish a fixed sleeping schedule to stay healthy and sharp the following day. Do not rob yourself of sleeping hours by cramming on certain tasks. Instead, focus on planning your day carefully so that you will have time to accomplish them all.

    1. Schedule your Important Tasks

    At this point, you would be able to see the times lots during the day when you do not have anything scheduled yet. If so, then you can refer to your list of priorities to allocate the different tasks into your day, week, or month.

    For example, if your most important task for the day is to write a thousand words for your personal book project, and if you do not have anything scheduled between seven and ten a.m., then you can block this task within this time.

    1. Schedule your Urgent Tasks

    After you have secured the times lots for your important tasks, you should then move on to blocking in the urgent ones. It helps to use a different colored-pen or highlighter to separate the important from the urgent.

    Do not forget to factor in breaks and an allowance in time for emergencies. In other words, you should never time-block one task after another without at least ten minutes of contingency time. This way, you will not be behind schedule in the next task when there was an unexpected extension in the task before it.

    Here is an example:

    •             Important Task —- 7:00 am to 9:00 am
    •             Contingency Time —- 9:00 am to 9:15 am
    •             Urgent Task —- 9:15 am to 11:30 am
    1. Review your schedule and make adjustments if necessary

    Once you have your entire day planned out, you can go back and assess your schedule as a whole. If you notice that you have spread yourself too thin, consider delegating certain tasks to others, rescheduling them, or canceling them altogether. Once you are satisfied with your schedule, the only thing left to do is to take action.

    As with any other skill, it takes constant practice to become better at scheduling and managing your time well. Nevertheless, it takes more than just scheduling and planning to do a great job every day without feeling burned out. That is because you also need to develop an efficient system. Read the post How to Make Establish an Efficient System? to learn more about that.

  • How to Learn of Hone Your Ability to Concentrate?

    How to Learn of Hone Your Ability to Concentrate?

    The ability to concentrate is a skill that becomes stronger over time. Through constant practice, you will be able to concentrate more effectively for an extended period of time. However, if you constantly find it difficult to focus on tasks, or if you find yourself wasting your time on unimportant activities, then you need to address this problem as soon as possible.

    Ability: Human Resource Management; An acquired or natural capacity or talent that enables an individual to perform a particular job or task successfully. See also aptitude. Law; The power to carry out a legal act or satisfy a legal obligation.

    Concentrate: A concentrate is a form of substance which has had the majority of its base component (in the case of a liquid: the solvent) removed. Typically, this will be the removal of water from a solution or suspension, such as the removal of water from fruit juice. One benefit of producing a concentrate is that of a reduction in weight and volume for transportation, as the concentrate can be reconstituted at the time of usage by the addition of the solvent. Completely different to clustered.

    The good news is that there are tested-and-proven tips on how you can concentrate better. Apply the following tips and notice how you will then be able to finish your important tasks on time.

    Eliminate distractions

    Distractions come in all shapes and sizes. It could be the uncomfortable chair you are sitting on, the messy desk you have to work on, or the loud noises from outside. Whatever your case may be, it is important to get rid of them before you begin your task. That way, you can no longer use them as an excuse to procrastinate.

    Here are some suggestions:

    I. Hang up a “do not disturb” sign.

    II. Play instrumental “concentration enhancing” music to drown out the background noise.

    III. Set your phone on silent mode and store it away.

    IV. Block certain websites that keep you from focusing.

    Focus on one task at a time

    Multi-tasking keeps you from being able to provide quality output. It also stresses your mind out, whether you are aware of it or not. This is because you are not really “accomplishing” multiple things at once, but rather you are rapidly switching from one task to another.

    Instead, set aside a time block for a particular task and do absolutely nothing else except that task within that time frame. You could even set a timer so that you will not have to glance at the clock every now and then to check how much time you have left.

    Take short breaks between tasks

    Most people – even the most productive ones out there – can concentrate on an important task for no more than two hours at a time. Likewise, it takes approximately fifteen minutes of rest to replenish this concentration “energy.” Therefore, you can use this as a rule of thumb to schedule breaks.

    For instance, after working non-stop on a task for two hours straight, set a timer to signal you to take a fifteen-minute break. Then, do something relaxing, such as taking a walk or having a snack. After fifteen minutes, you will be ready to take on another two-hour long task, give or take.

    Focus on challenging tasks during your peak hours

    Identify which part of the day you feel most confident and energized, and use this time to work on the tasks that require the most concentration. For most people, mornings are the times when they feel as if they can handle anything. For others, this happens during the evenings when everyone else is exhausted from work.

    Reward yourself after accomplishing a challenging task

    Our minds are programmed to repeat a certain behavior if we are rewarded for it. Therefore, to condition yourself to practice improving your concentration each day, do not forget to reward yourself after a job well done. It could be something as simple as playing a video game for an hour, watching an episode of your favorite television show, or enjoying a delicious, albeit sinful, snack. That way, you can be more driven to finish the task so that you can get your reward.

    Aside from these tips, it always helps to remind yourself to take good care of your body. Always make it a priority to get enough hours of sleep, eat nutritious meals, and hydrate throughout the day. When your body is healthy and full of energy, it is only natural for your mind to be sharp and focused.

    At this point, you must be excited to start working on your tasks. However, you might want to learn how to manage your schedule first, especially if you have multiple tasks to handle each day. Find out how you can acquire this skill in the post What is Master the Art of Scheduling?

  • How to Make Establish an Efficient System?

    How to Make Establish an Efficient System?

    Efficient (of a system or machine) achieving maximum productivity with minimum wasted effort or expense, preventing the wasteful use of a particular resource. Working in a well-organized and competent way. Performing or functioning in the best possible manner with the least waste of time and effort; having and using requisite knowledge, skill, and industry.

    Abraham Lincoln once gave a sound piece of advice regarding productivity. He said, “Give me six hours to chop down a tree and I will spend the first four sharpening the Axe.”

    It is apparent that he means that he can do a much more efficient job with the right tool. On the other hand, chopping away on the tree with a dull Axe might cut it down as well, but less efficiently and probably for a longer period of time. In other words, the best way to make the most of your time is by establishing an efficient system. To be more specific, you should first create the most conducive environment, and choosing the best tools, for the task.

    To help you establish an efficient system, there are two main things to do. The first one is to choose the right tools you need to accomplish the task in the best possible way. The second is to organize the space in which you will be doing the task.

    Choose the Best Tools for the Task

    Can you tell off the bat which tools you need the most to accomplish certain tasks? If you cannot, try remembering the following guidelines:

    1. The tool should be the most user-friendly.

    While this does not apply to all cases, it helps to remember to go back to the basics. Often, the tool that is easiest to use is also the more efficient. It does not require much time to learn how to use it and to manipulate it.

    An example of a simple, user-friendly time management tool is the to Do list. It is simple as jotting down tasks on a piece of paper and crossing them out once you are done.

    1. The tool should help you focus.

    Some people who want to enhance their time management skills often tend to buy a number of “organizational tools,” such as planners, calendars, and so on, but then end up not using most of them at all. Worse, some would attempt to use them all at once and end up confused. Therefore, the best solution is to pick no more than one tool you will truly use for a particular project, goal, or task, and then stick to it.

    1. The tool should be the most efficient and effective.

    If a tool requires too much time to set up before you can use it, then it had better be four times more efficient than the other models. Otherwise, you would only end up accumulating wasted time from using it. The bottom-line is to choose a tool that will strike a balance between efficiency and effectiveness by looking at how well it can help you with the task and how quickly it can be used.

    Aside from these, other factors you can consider are accessibility, cost, visibility, and so on, depending on the specific tools you need. After all, some tools are to be used for personal goals and tasks, while others are for professional use or team projects. Nevertheless, it helps to keep these three core guidelines in mind before you decide to choose a certain tool for your project.

    Organize and Develop an Efficient Work Space

    A space that is clean and organized does not just mean it is neat and tidy. Rather, it expands to keeping only the things you need in sight. Everything else that does not serve any purpose to your goal is merely a distraction. This rule applies not just to your physical surroundings, but your digital space as well.

    You can achieve this by taking these simple steps:

    1. Clear all the items off the area first. This will make it easier for you to separate the items and tools you want to use from the ones that only serve as distraction.

    For instance, if your computer desktop is cluttered with all sorts of icons and folders, then create a folder and label it “Mess.” After that, move everything into it in one full sweep.

    1. Re-build or re-organize the area by choosing the tools that you need. Everything else must be removed or stored away more efficiently.

    If we go back to the same example, when you are left with a clear desktop, you can then choose from the “Mess” folder the ones you need for a particular project or goal. Everything else can be deleted or sorted out until you can safely delete the “Mess” folder.

    1. Develop an efficient system for your project or goal.

    Now that only the tools you need remain in the area, your final step is to use them to create an efficient system. It is important to ensure that the system is simple, easy to use, and effective, because you may be using it so often it becomes a habit.

    Let us say you make a living as a medical transcriptionist. Since your desktop is now uncluttered, you now only have your transcribing tool, a spreadsheet icon of a file that helps you track your progress, and folder of projects on it. Your final step is to systematize how you work so that you can maximize your time and efficiency. It can be simple, such as:

    Step 1: Click the spreadsheet icon to monitor and review project.

    Step 2: Open transcribing tool.

    Step 3: Open project to be transcribed.

    Step 4: Put on headset, adjust volume, and start transcribing.

    Once your tools and system are polished and organized, it is guaranteed that all the tasks you need to accomplish will become easier to do. All you need to do at this point is to take action.

  • How to Set the Right Goals?

    How to Set the Right Goals?

    A goal is a desired result or possible outcome that a person or a system envisions, plans and commits to achieve: a personal or organizational desired end-point in some sort of assumed development. Many people endeavor to reach goals within a finite time by setting deadlines.

    It is roughly similar to purpose or aim, the anticipated result which guides reaction, or an end, which is an object, either a physical object or an abstract object, that has intrinsic value.

    Setting the Goals

    Goal setting may involve establishing specific, measurable, achievable, relevant, and time-bounded (SMART) objectives, but not all researchers agree that these SMART criteria are necessary.

    Research on goal setting by Edwin A. Locke and his colleagues suggests that goal setting can serve as an effective tool for making progress when it ensures that group members have a clear awareness of what each person must do to achieve a shared objective. On a personal level, the process of setting goals allows individuals to specify and then work toward their own objectives (such as financial or career-based goals). Goal-setting comprises a major component of personal development and management.

    Goals can be long-term, intermediate, or short-term. The primary difference is the time required to achieve them.

    Short-term goals

    Short-term goals expect accomplishment in a short period of time, such as trying to get a bill paid in the next few days. The definition of a short-term goal need not relate to any specific length of time. In other words, one may achieve (or fail to achieve) a short-term goal in a day, week, month, year, etc. The time-frame for a short-term goal relates to its context in the overall time line that it is being applied to. For instance, one could measure a short-term goal for a month-long project in days; whereas one might measure a short-term goal for someone’s lifetime in months or in years. Planners usually define short-term goals in relation to long-term goals.

    In any endeavor, the first step is to establish a clear goal. The more detailed and clear it is, the easier it will be for you to make choices and establish steps that you need to take towards accomplishing it.

    However, before getting into the subject of setting goals, let us first talk about the Goal-Setting Theory of Locke and Latham. Learning this will help you visualize the results that you truly want and need.

    Dr. Edwin Locke, the author of the article “Toward a Theory of Task Motivation and Incentives”, published in 1968, explained that people become motivated towards doing their job when they are given clear goals as well as proper feedback. He also pointed that having a specific and challenging goal motivates people to boost their performance.

    Twelve years later, Locke and Dr. Gary Latham published “A Theory of Goal Setting and Task Performance,” their seminal work. It not only highlighted the significance of setting definite and challenging goals, but also provided five key components that will guide you to set them successfully. These are Clarity, Challenge, Commitment, Feedback, and Task Complexity. Here are the steps on how you can use them:

    Establish clear goals.

    It is important to be detailed with what you want to accomplish. By doing so, you can track your progress and determine which areas you need to improve on and which ones are helping you to get closer to your goal.

    Perhaps the most efficient way to establish goals is by applying the SMART criteria. This was first explained by George T. Doran in the November 1981 issue of Management Review. It has since become the primary tool used in setting goals.

    “SMART” stands for Specific, Measurable, Achievable (or Assignable), Relevant, and Time-bound. Here is how you can apply each criterion:

    1. Specific – the goal has to be so clear it leaves no room for doubt. Detail what is important to you, what you expect from it, how you will know when it happens, and so on.
    2. Measurable – this puts emphasis on the need for measurable factors to help determine whether you are improving or not. Without measurable factors, you would find it impossible to stay motivated.
    3. Assignable or Achievable – a goal may be specific and measurable, but it can be unachievable if it is unrealistic. It is important to ensure that you can either achieve the goal-related tasks yourself, or assign some of the tasks to someone who can.
    4. Relevant – it is important to work towards a goal that is in line with your principles and purpose in life. For instance, you can consider whether the goal is worth the time, energy, and resources and if it is of true value to you.
    5. Time-bound – a time frame is an essential part of goal setting, because it helps you commit and increases your focus. A goal that is not time-bound is usually shipped off to “someday” land and never seen again. Therefore, you must set a target date.

    Here is an example of a SMART goal: “I will finish writing the first draft of my twenty-thousand-word romance fiction novel entitled “Oceans Away from Sarah” before December 25, 2016.”

    Set the Right Goals

    Ensure that the goals are challenging

    The more challenging yet realistic a goal is, the more motivated you will be to accomplish it. First, consider whether the goal you want makes you feel excited. Why does the thought of accomplishing it makes you feel good? Visualize the goal and determine the steps you need to take to turn it into a reality.

    Commit yourself to the goal

    Committing to your goal means that you are going to devote your time, energy, and resources to accomplish it. It also means you recognize its importance in your life and that you will not give up. It also helps to remember that plans can change, but the goal should remain the same.

    Track your Progress to Get Feedback

    As you work towards your goal, you must continuously enhance your skills, plans, and tools. That way, you can become even more efficient and effective. The only way to know how and what to improve on is by receiving feedback.

    Feedback is easily given by a team leader and one’s peers in major projects, but if you are on your own, then you need to track your own progress to receive it. Therefore, you must create a way to measure your progress as soon as you start working towards your goal. Through these standards, you can determine how far along you are.

    Calibrate the complexity of the task

    If a certain task towards your goal is too challenging it becomes unrealistic, you can take a step back and make the necessary adjustments. In other words, do not charge head-on if you are unprepared for it, because you will only end up feeling too pressured. This is dangerous, because it can cause you to give up altogether.

    Instead, consider the factors that are causing the task to be too complex. Reflect on whether you need more time, additional skills, or better tools for it. Maybe you need to break it down into smaller, more manageable parts. It is also possible that you need to delegate it to an expert. All these adjustments may even help you achieve your goal more efficiently.

    Once you have established a clear goal, the next step is to generate tasks that are in line with it. By doing so, you would then be able to determine the time you need to accomplish it. How to Set Your Organize Priorities? posts will help you to identify which tasks are important each day, and which ones to set aside.

  • 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.

  • 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.

  • What is The Chemical Basis of Life?

    What is The Chemical Basis of Life?

    Understanding of Chemical; A chemical substance is a form of matter that has the constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be chemical elements, chemical compounds, ions or alloys.

    Chemical substances are often called ‘pure’ to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are the diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.

    Chemical substances exist as solids, liquids, gases, or plasma, and may change between these phases of matter with changes in temperature or pressure. Chemical substances may be combined or converted to others by means of chemical reactions. Now you will understanding of The Chemical Basis of Life.

    Acids and Bases

    Acids are chemical compounds that release hydrogen ions (H+) when placed in water. For example, when hydrogen chloride is placed in water, it releases its hydrogen ions and the solution becomes hydrochloric acid.

    Bases are chemical compounds that attract hydrogen atoms when they are placed in water. An example of a base is sodium hydroxide (NaOH). When this substance is placed in water, it attracts hydrogen ions, and a basic (or alkaline) solution results as hydroxyl (–OH) ions accumulate.

    Molecule

    Most of the compounds of interest to biologists are composed of units called molecules. A molecule is a precise arrangement of atoms held together by chemical bonds, and a compound is a molecule that contains atoms of more than one element. A molecule may be composed of two or more atoms of the same element, as in oxygen gas (O2), or it may be composed of atoms from different elements. The arrangements of the atoms in a molecule account for the properties of a compound. The molecular weight is equal to the atomic weights of the atoms in the molecule.

    The atoms in molecules may be joined to one another by various linkages called bonds. One example of a bond is an ionic bond, which is formed when the electrons of one atom transfer to a second atom. This creates electrically charged atoms called ions. The electrical charges cause the ions to be attracted to one another, and the attraction forms the ionic bond.

    A second type of linkage is a covalent bond. A covalent bond forms when two atoms share one or more electrons with one another. For example, as shown in Figure 1, oxygen shares its electrons with two hydrogen atoms, and the resulting molecule is water (H2O). Nitrogen shares its electrons with three hydrogen atoms, and the resulting molecule is ammonia (NH3). If one pair of electrons is shared, the bond is a single bond; if two pairs are shared, it is a double bond.

    Formation of a covalent bond in water and ammonia molecules

    Figure 1. Formation of a covalent bond in water and ammonia molecules. In each molecule, the second shell fills with eight electrons.

    Organic Compound: The chemical compounds of living things are known as organic compounds because of their association with organisms and because they are carbon-containing compounds. Organic compounds, which are the compounds associated with life processes, are the subject matter of organic chemistry. Among the numerous types of organic compounds, four major categories are found in all living things: carbohydrates, lipids, proteins, and nucleic acids.

    Carbohydrates

    Almost all organisms use carbohydrates as sources of energy. In addition, some carbohydrates serve as structural materials. Carbohydrates are molecules composed of carbon, hydrogen, and oxygen; the ratio of hydrogen atoms to oxygen and carbon atoms is 2:1.

    Simple carbohydrates, commonly referred to as sugars, can be monosaccharides if they are composed of single molecules, or disaccharides if they are composed of two molecules. The most important monosaccharide is glucose, a carbohydrate with the molecular formula C6H12O6. Glucose is the basic form of fuel in living things. In multicellular organisms, it is soluble and is transported by body fluids to all cells, where it is metabolized to release its energy. Glucose is the starting material for cellular respiration, and it is the main product of photosynthesis

    Three important disaccharides are also found in living things: maltose, sucrose, and lactose. Maltose is a combination of two glucose units covalently linked. The table sugar sucrose is formed by linking glucose to another monosaccharide called fructose. (Figure 2 shows that in the synthesis of sucrose, a water molecule is produced. The process is therefore called a dehydration reaction. The reversal of the process is hydrolysis, a process in which the molecule is split and water is added.) Lactose is composed of glucose and galactose units.

    Glucose and fructose molecules combine to form the disaccharide sucrose

    Figure 2. Glucose and fructose molecules combine to form the disaccharide sucrose.

    Complex carbohydrates are known as polysaccharides. Polysaccharides are formed by linking innumerable monosaccharides. Among the most important polysaccharides is starch, which is composed of hundreds or thousands of glucose units linked to one another. Starch serves as a storage form for carbohydrates. Much of the world’s human population satisfies its energy needs with starch in the form of rice, wheat, corn, and potatoes.

    Two other important polysaccharides are glycogen and cellulose. Glycogen is also composed of thousands of glucose units, but the units are bonded in a different pattern than in starch. Glycogen is the form in which glucose is stored in the human liver. Cellulose is used primarily as a structural carbohydrate. It is also composed of glucose units, but the units cannot be released from one another except by a few species of organisms. Wood is composed chiefly of cellulose, as are plant cell walls. Cotton fabric and paper are commercial cellulose products.

    Lipids

    Lipids are organic molecules composed of carbon, hydrogen, and oxygen atoms. The ratio of hydrogen atoms to oxygen atoms is much higher in lipids than in carbohydrates. Lipids include steroids (the material of which many hormones are composed), waxes, and fats.

    Fat molecules are composed of a glycerol molecule and one, two, or three molecules of fatty acids (see Figure 3). A glycerol molecule contains three hydroxyl (–OH) groups. A fatty acid is a long chain of carbon atoms (from 4 to 24) with a carboxyl (–COOH) group at one end. The fatty acids in a fat may all be alike or they may all be different. They are bound to the glycerol molecule by a process that involves the removal of water.

    Certain fatty acids have one or more double bonds in their molecules. Fats that include these molecules are unsaturated fats. Other fatty acids have no double bonds. Fats that include these fatty acids are saturated fats. In most human health situations, the consumption of unsaturated fats is preferred to the consumption of saturated fats.

    Fats stored in cells usually form clear oil droplets called globules because fats do not dissolve in water. Plants often store fats in their seeds, and animals store fats in large, clear globules in the cells of adipose tissue. The fats in adipose tissue contain much concentrated energy. Hence, they serve as a reserve energy supply to the organism. The enzyme lipase breaks down fats into fatty acids and glycerol in the human digestive system.

    A fat molecule is constructed by combining a glycerol molecule with three fatty acid molecules

    Figure 3. A fat molecule is constructed by combining a glycerol molecule with three fatty acid molecules. (Two saturated fatty acids and one unsaturated fatty acid are shown for comparison.) The constructed molecule is at the bottom.

    Protein

    Proteins, among the most complex of all organic compounds, are composed of amino acids (see Figure 4), which contain carbon, hydrogen, oxygen, and nitrogen atoms. Certain amino acids also have sulfur atoms, phosphorus, or other trace elements such as iron or copper.

    The structure and chemistry of amino acids

    Figure 4. The structure and chemistry of amino acids. When two amino acids are joined in a dipeptide, the –OH of one amino acid is removed, and the –H of the second is removed. So, water is removed. A dipeptide bond (right) forms to join the amino acids together

    Many proteins are immense and extremely complex. However, all proteins are composed of long chains of relatively simple amino acids. There are 20 kinds of amino acids. Each amino acid (see the left illustration in Figure 4) has an amino (–NH2) group, a carboxyl (–COOH) group, and a group of atoms called an –R group (where R stands for radical). The amino acids differ depending on the nature of the –R group, as shown in the middle illustration of Figure 4. Examples of amino acids are alanine, valine, glutamic acid, tryptophan, tyrosine, and histidine.

    The removal of water molecules links amino acids to form a protein. The process is called dehydration synthesis, and a by-product of the synthesis is water. The links forged between the amino acids are peptide bonds, and small proteins are often called peptides.

    All living things depend on proteins for their existence. Proteins are the major molecules from which living things are constructed. Certain proteins are dissolved or suspended in the watery substance of the cells, while others are incorporated into various structures of the cells. Proteins are also found as supporting and strengthening materials in tissues outside of cells. Bone, cartilage, tendons, and ligaments are all composed of proteins.

    One essential function of proteins is as an enzyme. Enzymes catalyze the chemical reactions that take place within cells. They are not used up in a reaction; rather, they remain available to catalyze succeeding reactions.

    Every species manufactures proteins unique to that species. The information for synthesizing the unique proteins is located in the nucleus of the cell. The so-called genetic code specifies the amino acid sequence in proteins. Hence, the genetic code regulates the chemistry taking place within a cell. Proteins also can serve as a reserve source of energy for the cell. When the amino group is removed from an amino acid, the resulting compound is energy-rich.

    Nucleic acids: Like proteins, nucleic acids are very large molecules. The nucleic acids are composed of smaller units called nucleotides. Each nucleotide contains a carbohydrate molecule (sugar), a phosphate group, and a nitrogen-containing molecule that, because of its properties, is a nitrogenous base.

    Living organisms have two important nucleic acids. One type is deoxyribonucleic acid, or DNA. The other is ribonucleic acid, or RNA. DNA is found primarily in the nucleus of the cell, while RNA is found in both the nucleus and the cytoplasm, a semiliquid substance that composes the volume of the cell.

    DNA and RNA differ from one another in their components. DNA contains the carbohydrate deoxyribose, while RNA has ribose. In addition, DNA contains the base thymine, while RNA has uracil.

    Elements and Atoms

    For many centuries, biology was the study of the natural world. Biologists searched for unidentified plants and animals, classified them, and studied their anatomy and how they acted in nature. Then in the 1700s, scientists discovered the chemical and physical bases of living things. They soon realized that the chemical organization of all living things is remarkably similar.

    Elements: All living things on Earth are composed of fundamental building blocks of matter called elements. More than 100 elements are known to exist, including those that are man-made. An element is a substance that cannot be chemically decomposed. Oxygen, iron, calcium, sodium, hydrogen, carbon, and nitrogen are examples of elements.

    Atoms: Each element is composed of one particular kind of atom. An atom is the smallest part of an element that can enter into combinations with atoms of other elements.

    Atoms consist of positively charged particles called protons surrounded by negatively charged particles called electrons. A third type of particle, a neutron, has no electrical charge; it has the same weight as a proton. Protons and neutrons adhere tightly to form the dense, positively charged nucleus of the atom. Electrons spin around the nucleus.

    The electron arrangement in an atom plays an essential role in the chemistry of the atom. Atoms are most stable when their outer shell of electrons has a full quota. The first electron shell has a maximum of two electrons. The second and all other outer shells have a maximum of eight electrons. Atoms tend to gain or lose electrons until their outer shells have a stable arrangement. The gaining or losing of electrons, or the sharing of electrons, contributes to the chemical reactions in which an atom participates.