Tag: Process

What is the Process of Manpower Planning?
Manpower planning is the process of estimating. The optimum number of people required for completing a project, task, or goal within time. Manpower planning includes parameters like the number of personnel, different types of skills, time period, etc. It is a never-ending continuous process to make sure that the business has the optimized resources available. When required taking into consideration the upcoming future projects and also the replacement of the outgoing employees. It is also called Human Resource Planning. Also learn, The Steps of Manpower Planning with Features!

Explain is, What is the Process of Manpower Planning?

What is the process of Manpower Planning? The HR department of every company has to constantly keep an eye on the human resources that the company has. With every possible event like change industry dynamics, increase in business requirements, skills required for a particular technology, etc. The need for having better resources increases.

The process of manpower planning involves the following steps.

First of all the objectives and strategies regarding the diversification, expansion innovation, production, marketing, and finance of the organization are analyzed. So that a fair idea could make regarding the future HR needs of the organization. Because the organizational plans are based on labor, economic, sales, and expansion forecasts. It serves as a good foundation for manpower planning.

The next step is forecasting the demand for human resources. There are many techniques available for forecasting the HR demand like managerial judgment, ratio-trend analysis, and mathematical models. The supply of manpower is also taken into consideration from internal and external sources. The difficulties faced during the process of manpower planning are uncertainties that can be caused by absenteeism; seasonal employment and labor turnover.

As well as, The other uncertainties that make the manpower planning process less reliable are technology changes and market conditions. Sometimes the employees and their unions also resist the manpower planning process because they erroneously feel that manpower planning could increase the workload of the employees. Another limitation faced by the process of manpower planning is that the information system regarding the human resources of an organization is not fully developed in some countries.

The Main Process and Steps for having manpower planning.

The Main Process and Steps for having manpower planning are as below:

Understanding the existing workforce:

The HR department has to thoroughly understand the manpower available to the company. They should examine the background, skill set, qualification, location, etc of the entire workforce so that they have a good idea regarding the pool of talent which the company has.

Forecasting for the future:

With constant changes in business requirements, companies must understand the future trend and which type of employees would best suit their organization. Hence, companies must examine, evaluate and forecast the type of employee workforce they want in the future years

Recruitment and selection:

Depending on the business requirements, manpower planning leads to a much better thought-out recruitment and selection pattern. This totally depends upon the forecasts made and the business requirements. Hence, candidates with better qualifications, skill set, experience, etc are shortlisted as employees to best suit future needs.

Training the employees:

Employees who are a part of the organization are training to have the best skills, knowledge, and understanding about the current job as well as the future requirements.

All these above-mentioned manpower planning steps help organizations become better prepared to adapt to new technology, future industry developments and even to face off with competitors.

Multi-Steps Process of Manpower Planning:

The planning process is one of the most crucial, complex, and continuing managerial functions which, according to the Tata Electrical Locomotive Company, “embraces organization development, managerial development, career planning, and succession planning”. The process has gained importance in India with the increase in the size of business enterprises, complex production technology, and the adoption of professional management techniques. Also learn, Case Study on Debt Collection Management!

It may rightly regard as a multi-step process, including various issues, such as:
- Deciding goals or objectives.
- Auditing of the internal resources.
- Formulation of the recruitment plan.
- Estimating future organizational structure and manpower requirements, and.
- Developing a human resource plan.
A. Deciding Goals or Objectives:

The business objectives have been determining; planning of manpower resources has to fully integrate into the financial planning. It becomes necessary to determine how the human resources can organize to achieve these objectives.

For this purpose, a detailed organization chart is drawn and the management of the company tries to determine. “How many people, at what level, at what positions and with what kind of experience and training would require meeting the business objectives during the planning period”. The management of this company considers a time 5 pan of five years as an optimum period for this purpose.

It stresses the specific and standard occupational nomenclature that must use without. “Which it would not be possible to build a firm-cum-industry-wise manpower resources planning”. It suggests the adoption for this purpose of the international coding of occupations. For sound manpower planning, it considers as a prerequisite the preparation of a manual of job classification and job description with specific reference to individual jobs to perform.

B. Audit of the Internal Resources:

The next step consists of an audit of the internal resources. A systematic review of the internal resources would indicate persons. Within the organizations that possess different or higher levels of responsibilities. Thus it becomes necessary to integrate into the manpower planning process a sound system of performance appraisal as well as an appraisal of the potential of existing employees.

C. Formulation of the Recruitment Plan:

A detailed survey of the internal manpower resources can ultimately lead to an assessment of the deficit or surplus of personnel for the different levels during the planned period. Whilst arriving at the final figures, it is necessary to take them into account. “The actual retirements and estimate loss due to death, ill-health and turnover, base on experience and future outlook about company’s expansion and future growth patterns”.

D. Estimating Future Organisational Structure and Manpower Requirements:

The management must estimate the structure of the organization at a given point in time. For this estimate, the number and type of employees needed have to determine. Many environmental factors affect this determination. They include business forecast, expansion and growth, design and structural changes, management philosophy, government policy, product, and human skills mix, and competition.

E. Developing of Human Resource Plan:

This step refers to the development and implementation of the human resource plan. Which consists in finding out the sources of labor supply with a view to making an effective use of these sources. As well as, The first thing, therefore, is to decide on the policy— should the person hire from within through promotional channels or should it obtain from an outside source.

Also, The best policy which is following by most organizations is to fill up higher vacancies by promotion and lower-level positions by recruitment from the labor market. The market is a geographical area from which employers recruit their workforce and labor seeks employment.

What is the Process of Manpower Planning? Thanks, Also, Credit Photo pixabay.com/
March 17, 2018
Processes of Scientiﬁc Management
Explaining The Processes of Scientiﬁc Management!

Management is an art and science and it is a continuous activity. It is a factor of production and it is an organized activity. Management aims at maximizing proﬁt with ethical behavior. It is a profession by itself and involves decision making. It is needed in all levels and develops leadership qualities in people. Planning, organizing, stafﬁng, directing, coordinating, motivating and controlling are the functions of management. How to Explain Techniques of Scientific Management?

Seven types of Processes of Scientiﬁc Management
- Planning.
- Organizing.
- Stafﬁng.
- Directing.
- Coordinating.
- Motivating, and.
- Controlling.
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Explanation of following Processes of Scientiﬁc Management

Planning

The process of making plans for something.

The control of urban development by a local government authority, from which a license must be obtained to build a new property or change an existing one.

Organizing

Arrange systematically; order. coordinate the activities of (a person or group) efficiently. form (a number of people) into a trade union or other political group.

Make arrangements or preparations for (an event or activity). take responsibility for providing or arranging.

Stafﬁng

Staffing is the process of hiring, positioning and overseeing employees in an organization.

Definition of staffing: The selection and training of individuals for specific job functions, and charging them with the associated responsibilities.

Directing

Control the operations of; manage or govern. supervise and control (a film, play, or other production, or the actors in it).

Aim (something) in a particular direction or at a particular person. focus (one’s thoughts) on or address (one’s efforts) towards something.

Give (someone) an official order or authoritative instruction.

Coordinating

Bring the different elements of (a complex activity or organization) into a harmonious or efficient relationship. negotiate with others in order to work together effectively. match or harmonize attractively.

Motivating

Provide (someone) with a reason for doing something. cause (someone) to have an interest in or enthusiasm for something. request (something) and present facts and arguments in support of one’s request.

Controlling

Determine the behavior or supervise the running of. maintain influence or authority over. limit the level, intensity, or numbers of. remain calm and reasonable despite provocation.

Take into account (an extraneous factor that might affect the results of an experiment).

What is Scientific Management; Also called Taylorism is a theory of management that analyzes and synthesizes workflows. Its main objective is improving economic efficiency, especially labor productivity. It was one of the earliest attempts to apply science to the engineering of processes and to management. How Do You Know Your Company Wants Help From The Outside?

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Notes: You will come to know the deﬁnitions of all the seven Processes of Scientiﬁc Management; Planning, Organizing, Stafﬁng, Directing, Coordinating, Motivating, Controlling.
January 14, 2018
What is Phases of the Data Mining Process?

What is Phases of the Data Mining Process?

The Cross-Industry Standard Process for Data Mining (CRISP-DM) is the dominant data-mining process framework. It’s an open standard; anyone may use it. The following list describes the various phases of the process.

The Cross-Industry Standard Process for Data Mining

Business understanding

In the business understanding phase:

First, it is required to understand business objectives clearly and find out what are the business’s needs.

Next, we have to assess the current situation by finding of the resources, assumptions, constraints and other important factors which should be considered.

Then, from the business objectives and current situations, we need to create data mining goals to achieve the business objectives within the current situation.

Finally, a good data mining plan has to be established to achieve both business and data mining goals. The plan should be as detailed as possible.

Data understanding

First, the data understanding phase starts with initial data collection, which we collect from available data sources, to help us get familiar with the data. Some important activities must be performed including data load and data integration in order to make the data collection successfully.

Next, the “gross” or “surface” properties of acquired data need to be examined carefully and reported.

Then, the data needs to be explored by tackling the data mining questions, which can be addressed using querying, reporting, and visualization.

Finally, the data quality must be examined by answering some important questions such as “Is the acquired data complete?”, “Is there any missing values in the acquired data?”

Data preparation

The data preparation typically consumes about 90% of the time of the project. The outcome of the data preparation phase is the final data set. Once available data sources are identified, they need to be selected, cleaned, constructed and formatted into the desired form. The data exploration task at a greater depth may be carried during this phase to notice the patterns based on business understanding.

Modeling

First, modeling techniques have to be selected to be used for the prepared dataset.

Next, the test scenario must be generated to validate the quality and validity of the model.

Then, one or more models are created by running the modeling tool on the prepared dataset.

Finally, models need to be assessed carefully involving stakeholders to make sure that created models are met business initiatives.

Evaluation

In the evaluation phase, the model results must be evaluated in the context of business objectives in the first phase. In this phase, new business requirements may be raised due to the new patterns that have been discovered in the model results or from other factors. Gaining business understanding is an iterative process in data mining. The go or no-go decision must be made in this step to move to the deployment phase.

Deployment

The knowledge or information, which we gain through data mining process, needs to be presented in such a way that stakeholders can use it when they want it. Based on the business requirements, the deployment phase could be as simple as creating a report or as complex as a repeatable data mining process across the organization. In the deployment phase, the plans for deployment, maintenance, and monitoring have to be created for implementation and also future supports. From the project point of view, the final report of the project needs to summary the project experiences and review the project to see what need to improved created learned lessons.

The CRISP-DM offers a uniform framework for experience documentation and guidelines. In addition, the CRISP-DM can apply in various industries with different types of data.

In this article, you have learned about the data mining processes and examined the cross-industry standard process for data mining.

Something is not Forgetting What? Data mining is a promising and relatively new technology. Data mining is defined as a process of discovering hidden valuable knowledge by analyzing large amounts of data, which is stored in databases or data warehouse, using various data mining techniques such as machine learning, artificial intelligence(AI) and statistical.

Many organizations in various industries are taking advantages of data mining including manufacturing, marketing, chemical, aerospace… etc, to increase their business efficiency. Therefore, the needs for a standard data mining process increased dramatically. A data mining process must be reliable and it must be repeatable by business people with little or no knowledge of data mining background. As the result, in 1990, a cross-industry standard process for data mining (CRISP-DM) first published after going through a lot of workshops, and contributions from over 300 organizations.

August 19, 2017
Process of The Data Mining

Process of The Data Mining

Data mining is a promising and relatively new technology. Data mining is defined as a process of discovering hidden valuable knowledge by analyzing large amounts of data, which is stored in databases or data warehouse, using various data mining techniques such as machine learning, artificial intelligence(AI) and statistical.

Many organizations in various industries are taking advantages of data mining including manufacturing, marketing, chemical, aerospace… etc, to increase their business efficiency. Therefore, the needs for a standard data mining process increased dramatically. A data mining process must be reliable and it must be repeatable by business people with little or no knowledge of data mining background. As the result, in 1990, a cross-industry standard process for data mining (CRISP-DM) first published after going through a lot of workshops, and contributions from over 300 organizations.

The data mining process involves much hard work, including perhaps building data warehouse if the enterprise does not have one. A typical data mining process is likely to include the following steps:

Requirements analysis: The enterprise decision makers need to formulate goals that the data mining process is expected to achieve. The business problem must be clearly defined. One cannot use data mining without a good idea of what kind of outcomes the enterprise is looking for, since the technique to be used and the data that is required are likely to be different for different goals. Furthermore, if the objectives have been clearly defined, it is easier to evaluate the results of the project. Once the goals have been agreed upon, the following further steps are needed.

Data selection and collection: This step may include finding the best source databases for the data that is required. If the enterprise has implemented a data warehouse, then most of the data could be available there. If the data is not available in the warehouse or the enterprise does not have a warehouse, the source OLTP (On-line Transaction Processing) systems need to be identified and the required information extracted and stored in some temporary system. In some cases, only a sample of the data available may be required.

Cleaning and preparing data: This may not be an onerous task if a data warehouse containing the required . data exists, since most of this must have already been done when data was loaded in the warehouse. Otherwise this task can be very resource intensive and sometimes more than 50% of effort in a data mining project is spent on this step. Essentially a data store that integrates data from a number of databases may need to be created. When integrating data, one often encounters problems like identifying data, dealing with missing data, data conflicts and ambiguity. An ETL (extraction, transformation and loading) tool may be used to overcome these problems.

Data mining exploration and validation: Once appropriate data has been collected and cleaned, it is possible to start data mining exploration. Assuming that the user has access to one or more data mining tools, a data mining model may be constructed based on the enterprise’s needs. It may be possible to take a sample of data and apply a number of relevant techniques. For each technique the results should be evaluated and their significance interpreted. This is likely to be an iterative process which should lead to selection of one or more techniques that are suitable for further exploration, testing, and validation.

Implementing, evaluating, and monitoring: Once a model has been selected and validated, the model can be implemented for use by the decision makers. This may involve software development for generating reports, or for results visualization and explanation for managers. It may be that more than one technique is available for the given data mining task. It is then important to evaluate the results and choose the best technique. Evaluation may involve checking the accuracy and effectiveness of the technique. Furthermore, there is a need for regular monitoring of the performance of the techniques that have been implemented. It is essential that use of the tools by the managers be monitored and results evaluated regularly. Every enterprise evolves with time and so must the data mining system. Therefore, monitoring is likely to lead from time to time to refinement of tools and techniques that have been implemented.

Results visualization: Explaining the results of data mining to the decision makers is an important step of the data mining process. Most commercial data mining tools include data visualization modules. These tools are often vital in communicating the data mining results to the managers, although a problem dealing with a number of dimensions must be visualized using a two dimensional computer screen or printout. Clever data visualization tools are being developed to display results that deal with more than two dimensions. The visualization tools available should be tried and used if found effective for the given problem.

August 19, 2017
The Creative Process

The Creative Process

Creativity is a phenomenon whereby something new and somehow valuable is formed. The created item may be intangible (such as an idea, a scientific theory, a musical composition, or a joke) or a physical object (such as an invention, a literary work, or a painting).

Scholarly interest in creativity involves many definitions and concepts pertaining to a number of disciplines: engineering, psychology, cognitive science, education, philosophy (particularly philosophy of science), technology, theology, sociology, linguistics, business studies, songwriting, and economics, covering the relations between creativity and general intelligence, mental and neurological processes, personality type and creative ability, creativity and mental health; the potential for fostering creativity through education and training, especially as augmented by technology; the maximization of creativity for national economic benefit, and the application of creative resources to improve the effectiveness of teaching and learning.

The Creative process can be broken into stages:

Preparation

This is the first phase, which most people call “work.” A writer, for example, prepares by writing, by reading, or by revising earlier work. A musician plays scales, chords, or songs; a painter messes with paints or visits an art gallery; an entrepreneur researches problems to solve; a programmer plays with code. In each example, the creative is going through relatively mundane processes.

The reason I say most people call this phase “work” is that these processes may or may not be inherently enjoyable. They’re also fairly mundane and tedious, but the creative has learned that this process is necessary to plant the seeds that lead to…Preparation is the background, experience, and knowledge that an entrepreneur brings to the opportunity recognition process. Just as an athlete must practice to excel, an entrepreneur needs the experience to spot opportunities. Over time, the results of research suggest that as much as 50 to 90 percent of start-up ideas emerge from a person’s prior work experience.

Incubation

Incubation is the stage during which a person considers an idea or thinks about a problem; it is the “mulling things over” phase. Sometimes incubation is a conscious activity, and sometimes it is unconscious and occurs while a person is engaged in another activity. One writer characterized this phenomenon by saying that “ideas churn around below the threshold of consciousness.”

This would be the mystical process if there were one, because you often don’t know that you’re incubating an idea, or if you do know you’re working on one, you don’t know when it’s going to come out. It’s during this phase that your conscious and subconscious minds are working on the idea, making new connections, separating out unnecessary ideas, and grabbing for other ideas.

This is the phase that most people mess up the most with distractions and the hustle and bustle of daily lives. Modern life, with its many beeps, buzzes, and distractions, has the strong tendency to grab the attention of both our subconscious and our unconscious mind, and as result, the creative process stops and is instead replaced by more immediate concerns.

Insight

Insight is the flash of recognition when the solution to a problem is seen or an idea is born. It is sometimes called the “eureka” experience. In a business context, this is the moment an entrepreneur recognizes an opportunity. Sometimes this experience pushes the process forward, and sometimes it prompts an individual to return to the preparation stage. For example, an entrepreneur may recognize the potential for an opportunity but may feel that more knowledge and thought is required before pursuing it.

Evaluation

Evaluation is the stage of the creative process during which an idea is subjected to scrutiny and analyzed for its viability. Many entrepreneurs mistakenly skip this step and try to implement an idea before they’ve made sure it is viable. Evaluation is a particularly challenging stage of the creative process because it requires an entrepreneur to take a candid look at the viability of an idea.

Elaboration

Elaboration is the stage during which the creative idea is put into a final form: The details are worked out and the idea is transformed into something of value, such as a new product, service, or business concept. In the case of a new business, this is the point at which a business plan is written.

Illumination

This is the “Eureka” moment that many of us spend our days questing after. When it hits, the creative urge is so incredibly strong that we lose track of what else is happening. The driving impulse is to get whatever is going on in our heads down into whatever medium it’s intended for.

The most frustrating thing for me is that the “illumination” moments happen at the most inopportune times. They invariably happen when I’m in the shower when I’m driving by myself, when I’m working out, or when I’m sitting in mind-numbing meetings that I can’t get out of. Of course, the bad part is as I said above: the impulse is to get the idea out as soon as possible, so it’s not at all uncommon for me to stop showering, driving, or working out and run to the nearest notepad – and, in meetings, I start purging immediately anyway. I’ve yet to gain enough clout to excuse myself from the meetings, but I’m working on it.

I was speaking to a friend a few weeks ago, and I told her I was frustrated because I was pregnant with ideas and didn’t have time to get them out. Keeping with the analogy, when a Eureka! moment hits, it’s much like labor – you’re done with incubating, and it’s time for…

Implementation

This phase is the one in which the idea you’ve been preparing and incubating sees the light of day. It’s when that written piece comes out, when that song flows when that canvas reveals its painting, and so on. It’s also when a good creative starts to evaluate the idea and determine whether it’s good or not – but only after they have enough to see where it’s going.

Most of the creative I know or work with get really frustrated with others during this phase. Other people only see the creation at the end, and they don’t recognize or care much about the process that generated that idea. This is especially true with some supervisors and bosses who expect the end product on a certain schedule, even though the creative process does not work that way. Creative know that for every good idea, there are at least a few that don’t work out, but they can’t know ahead of time what’s going to work out and what won’t.

The creative process begins with work and ends with work. The takeaway point here is that creativity is not just percolating and Eureka: it’s percolating and Eureka sandwiched between work phases.

April 10, 2017
Attribution and Motivation Among Ethnicity

Understanding of Attribution and Motivation Among Ethnicity?

What is Ethnicity? Meaning of Ethnicity “The fact or state of belonging to a social group that has a common national or cultural tradition.” Some about of Ethnic; Relating to a population subgroup (within a larger or dominant national or cultural group) with a common national or cultural tradition. Relating to national and cultural origins. Denoting origin by birth or descent rather than by present nationality. Characteristic of or belonging to a non-Western cultural tradition.

An ethnic group or ethnicity is a category of people who identify with each other based on similarities, such as common ancestral, language, social, cultural or national experiences. Unlike other social groups (wealth, age, hobbies), ethnicity is often an inherited status based on the society in which one lives. In some cases, it can be adopted if a person moves into another society. Membership of an ethnic group tends to be defined by a shared cultural heritage, ancestry, origin myth, history, homeland, language or dialect, symbolic systems such as religion, mythology and ritual, cuisine, dressing style, art, and physical appearance.

Ethnic groups, derived from the same historical founder population, often continue to speak related languages and share a similar gene pool. By way of language shift, acculturation, adoption and religious conversion, it is sometimes possible for individuals or groups to leave one ethnic group and become part of another (except for ethnic groups emphasizing racial purity as a key membership criterion).

Ethnicity is often used synonymously with ambiguous terms such as nation or people. In English, it can also have the connotation of something exotic (cf. “White ethnic”, “ethnic restaurant”, etc.), generally related to cultures of more recent immigrants, who arrived after the founding population of an area was established.

Now reading – Attribution and Motivation Among Ethnicity; Do attributional explanations for success and failure act as an important motivational force in different ethnic groups? According to Graham (1989,1994), because attributional theory considers the role of thought in determining behavior, it is particularly fruitful in examining motivation in different cultures and ethnic groups.

Beliefs About Effort and Ability

Are attributional belief patterns similar among different ethnic groups? A comparison of poor African-American, Hispanic, Indo-Chinese, and White fifth- and sixth-grade students found similar attribution patterns for all groups (Bempechat, Nakkula, Wu, & Ginsberg, 1996). All groups rated ability as the most important factor for success in math. In a subsequent study comparing African-American, Hispanic, Indo-Chinese, and White fifthand sixth-graders, Bempechat, Graham, and Jimenez (1999) found cultural similarities as well as cultural specifics. For all ethnic groups, failure was attributed to lack of ability and success to external factors. In contrast, Indo-Chinese students had stronger beliefs that failure was due to lack of effort. Attribution for failure due to lack of ability is a problem for all students because it is believed to be uncontrollable.

Graham (1984) compared middle- and low-SES African-American and White students on attributions for failure following a problem-solving task. The middle-class children in both ethnic groups were more likely to attribute failure to lack of effort and maintained consistently higher expectancies for success after experiencing failure. For both groups, this is indicative of an adaptive attributional pattern following failure, similar to that found in research by Diener and Dweck (1978). The findings of this research are important because they demonstrate the positive motivation pattern of African-American students—a pattern that has received little attention.

Stevenson and Lee (1990) compared beliefs of American and Asian students concerning the role of effort and ability for success in mathematics. They asked mothers in Minnesota, Japan, and Taiwan to assign 10 points among ability, effort, task difficulty, and luck to rank their importance in academic success and school performance. All the mothers assigned the points in the same rank order: (1) effort, (2) ability, (3) task, and (4) luck. American mothers scored ability and effort as about equal. In contrast, Taiwanese and Japanese mothers assigned effort a higher value than ability. Peak (1993) noted that, in Japanese elementary schools, ability is rarely mentioned, whereas effort is consistently portrayed as key to success. In contrast, in the United States, students who try very hard are often labeled nerd or grind.

These perceptions of effort and ability take on increased importance when homework is considered in the context of effort. Japanese and Chinese students spend at least twice the amount of time and effort on homework than do American students (Stevenson & Lee, 1990). American teachers assign less and consider it less valuable. Peak (1993) pointed out that homework reflects teachers’ beliefs on whether extra practice makes a difference and whether students are willing to engage in extra effort on behalf of their studies. American parents do not appear to consider good study habits as critical to academic success as do Asian parents.

Implications for Teachers

What can teachers draw from the attributional beliefs among different ethnic groups in terms of classroom practice? The important issue is to understand the motivational processes, such as attribution, operating within a particular ethnic group (Bempechat et al., 1996; Graham, 1994). When similarities are found across ethnic groups, educational interventions do not necessarily have to be targeted to children differentially based on their ethnic group membership.

Graham (1989) emphasized the importance of teacher feedback in influencing concepts of ability and expectations of minority, low-SES students. Recall the previous discussion of indirect attributional cues. It is important to be aware of feedback that may indirectly convey to students that they have low ability. Graham (1994) suggested that in view of the number of African- American children in negative educational situations, it is especially important to be sensitive to how minorities feel, think, and act in response to non-attainment of goals.

March 30, 2017
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.

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.

March 21, 2017
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

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):

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

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).

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.

March 21, 2017
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

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.

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

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.

March 20, 2017
What is the authority? Introduction, Meaning, and Definition

Authority is a legal power which is possessed by a person from his superior officers and with the help of which he succeeds in getting the things done by his sub-ordinates. Authority is the key to managerial functions. If the managers do not possess the required authorization, they will not be able to perform their duties properly.

Here are explain; What is the authority? Introduction, Meaning, and Definition.

A manager is in a position to influence his subordinates only by the use of his authority. It is the authorization which enables him to discharge the important functions of planning, coordination, motivation and controlling, etc. in an enterprise.

If proper authorization is not vesting in him, he cannot perform. These functions in the required manner and he cannot hold responsible for all these functions in the absence of proper authorities. It is only the authorities by virtue of which he dominates his subordinates and gets work done by them.

The word authority (derived from the Latin word Auctoritas) can use to mean the right to exercise power given by the State (in the form of government, judges, police officers, etc.), or by academic knowledge of an area (someone that can be an authority on a subject).

What is authority? Introduction, Meaning, and Definition #Pixabay.

The power or right to give orders, make decisions and enforce obedience. The right to act in a specified way delegated from one person or organization to another. A person or organization having political or administrative power and control. The power to influence others, especially because of one’s commanding manner or one’s recognized knowledge about something. A person with extensive or specialized knowledge about a subject; an expert.

Meaning of authority:

Authority is the power to make decisions, which guide the action of others. A delegation of authorization contributes to the creation of an organization. No single person is in a position to discharge all the duties in an organization. In order to ﬁnish the work in time, there is a need to delegate authorization and follow the principles of division of labor. Delegation permits a person to extend his inﬂuence beyond the limits of his own personal time, energy, and knowledge. It is the “right of decision and command.” Theories Sources with Characteristics of Authority.

Deﬁnition of authority:

The Following definitions below are from different authors;

According to Henry Fayol,

“Authority is the right to give orders and the power to exact obedience.”

According to Koontz and O’Donnell,

“Authority is the power to command others to act or not to act, in a manner deemed by the possessor of the authority to further enterprises or departmental purposes.”

According to Terry,

“Authority is the power to exact others to take actions considered appropriate for the achievement of a predetermined objective.”

According to Barnard,

“Authority is the character of a communication (order) in a formal organization by virtue of which it is accepted by a contributor to or member of the organization as governing the action he contributes. That is, as governing or determining what he does or is not to do so far as the organization is concerned.”

While concluding the meaning of authority it can say that authorities in the ordinary sense of the term are nothing more than a legal right. It empowers an individual to make decisions. He is giving a right to command and to exercise control over. Those who are responsible for the execution of policies and programs of the enterprise. For decisions take the authorizing person is holding responsible and is made answerable to his superiors and the organization as a whole.

January 19, 2017