Role of the Cells in the Human Body

3795 words (15 pages) Essay in Physiology

23/09/19 Physiology Reference this

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Understanding the Human Body and the Cells.

 

Abstract

The cells are the very structure of all known living organisms. While they are the smallest unit of life, they are essentially the foundation off all life. They contain a microscopic structure consisting of a nuclear and cytoplasmic material contained within a semi-permeable membrane. Some organisms are unicellular, which means it is only a single cell, however, some organisms like humans are multicellular. Within this report there will be a written commentary on a number of topics to show an overall understanding of cells within the body. This will be presented via tables and pictures, which can be found in the appendices.

Table of content

Title page 1

Abstract 2

Title page 3

Introduction 4

Discussion 7

Conclusion 8

References 9

Appendices  10

Introduction

Cells are the building blocks of life, consisting of a self contained and maintained environments, it consumes nutrients and then converts these nutrients into energy which carries out specialized functions throughout the body. Each cell within the body holds a set of instructions that differs from every other cell. Yet all living things are made of cells and all cells share certain functions and characteristics.

These characteristics of cells are; Growth & Development, Homeostasis, Movement, Reproduction, Energy use.  Growth refers to the cells growing to their sizes and then ceasing due to intrinsic and extrinsic factors. Homeostasis refers to the need of a stable environment for the survival of the cells. Cell membranes allow the cells to regulate the environment inside the cells. They control for instance, the amount of water that enters the cells and then leaves, to preserve the equilibrium of the water.  All cells move in some way or the other. Many cells move independently of one another and move as a result of external structures that propel the cells through the liquids of the body. Most cells reproduce through mitosis. Cells duplicate themselves and results in two daughter cells that have the exact same genetic material than the original cells. Lastly, all cells need energy to function. Energy typically takes the form of adenosine troposphere or ATP. In most cells, glucose reacts with oxygen to product ATP. Thus, all forms of energy ultimately come from plant cells either in the form of photosynthesis if consuming plants or plant-eating organisms. (National center for General Medical Sciences, 2017).

Cells can be split into two categories, prokaryotic (see Figure 1) and eukaryotic (see Figure 2)

Prokaryotic cells lake the internal membrane-bound structure and are unicellur organisms. Whereas, Eukaryotic cells are multicellular organisms that have membrane-bound organelles. Prokaryotic cells are tiny compared to eukaryotic cells.

Under examination of Eukaryotic cells, they consists of organelles all of which have specific functions for the survival of the cell. The structure of the cells and the functions they is a complex structure which depends on each part to function.

Whereas, a virus is a sub-microscopic infectious agent unable to grow or reproduce outside of another living cell.  They are of a cellular nature meaning they have no cells. Its makeup consists of a nucleic acid, which is enclosed with a capsid. It uses the host cell metabolic facilities and ribosome’s to create components to assemble visions.

Table1. Comparison of Prokaryotic and Eukaryotic cells.

Similarities

Prokaryotic cells

Eukaryotic  cells

Nucleus

DNA is found within the nucleus of the cell.

 Division happens via mitosis.

Nucleus is known as a nucleoid which is not a true nucleus. (Wiley & Sons, 2014).

DNA is more complex.

It is found within the middle of the cell and holds the DNA together.

Division happens via meiosis.

Ribosome

Responsible for making protein within the cytoplasm. Smaller than Eukaryotic

Bigger than in Prokaryotic cells.

Cytoplasm

Liquid material that contains DNA and other parts of the cell to function.

DNA contained within the nucleus is in the cytoplasm outside the nucleus.

Differences

Chloroplasts

Only found within plant or algae cells which are eukaryotic

Only found in eukaryotic cells and are responsible for extracting food from the sun and CO2.

Golgi apparatus

This is not found as the cell is not as complex as a eukaryotic cell.

Materials are transported through the cytoplasm

Mitochondria

Respiration takes place within the mesosome. ATP is not required within prokaryotic cells. As they can use passive transport.

Respiration takes place and ATP is produces creating energy for cell reactions.

Rough and smooth endoplasmic reticulum

Does not produce lipids.

Smooth endoplasmic adds carbohydrates and proteins and produces lipids. Rough is responsible for synthesizing proteins needed for the cells and environment around the cells.

The differences between viruses, prokaryotic cells and eukaryotic cells can be defined by the eukaryotic cell being much more complex. Below is a simple table in which the structure is detailed.

An organelle is a membrane bound structure found within the cell. Just like other cells, these mini-organs are bound in a double layer of phospholipids to insulate within the larger cell. A simpler way of thinking of organelles is to think of them as parts of a factory in which, they help specific tasks

Organelle

Function

Factory part

Nucleus

DNA Storage

Room where the instructions are kept

Mitochondrion

Energy production

Power plant

Smooth Endoplasmic Reticulum (SER)

Lipid production;

Detoxification

Accessory production

Rough Endoplasmic Reticulum (RER)

Protein production

Primary production line

Golgi apparatus

Protein modification

Shipping department

Peroxisome

Lipid destruction

Waste removal

Lysosome

Protein destruction

Recycling

Stems cells have the potential to develop into various types of cells during their early growth. They also serve as internal repair system, holding the ability to divide to replenish other cells. When division occurs, the new cells have the ability to remain as a cell stem or to become a different cell with a more specialized function. They are distinguished from other cells by two characterized. Firstly, as mentioned beforehand they are cabale of renewing themselves through cell division and secondly, they can become tissue or organ. (SC Primer, 2009).  Stem cells differ from all other types of cells within the body. All stem cell have three general properties: 1) they are capable of dividing and renewing themselves; 2) they are unspecialized; and 3) they can give rise to specialized cell types.

Nutrients are necessary for all living cells and organism in order to live. However, it causes toxic and unwanted produce and therefore, it is important that cells are able to regulate the substances within and outside the cell. This is controlled by the cell membrane. It consists of proteins, carbohydrates and phospholipids. The molecules are arranged in a mosaic like structure and the proteins are then placed throughout giving it the mosaic features. The phospholipid forms a double layer.  The phospholipids molecules all face outwards and away from water. This creates a barrier which blocks all the smallest molecules and the proteins use this to transport themselves around the body, (Brown, 1996).

Furthermore, there are several more transportation devices that transport nutrients around the body. Lipid diffusion transport soluble molecules like oxygen and water around the body. Osmosis refers the transport of water by diffusion across the membrane. Then there is passive transport which uses facilitated diffusion to transfer protein. Then there is active transport which involves pumping nutrients from low to high concentration across membranes (Koga, 2012).

Alongside nutrients energy is needed for all living things for growth, movement, homeostasis and cell division. As mentioned above, nutrients are needed for the growth and division to happen.  Movement of nutrients within the cells consists of endocytosis, exocytosis and active transport. This allows homeostasis to occur and energy to be obtained, whether it is in chemical or physical forms. This in terms of animal cells is when chemical energy is changed to kinetic and heat energy.

Nucleic acids are the sources of information. They consist of nucleotides and their functions are related to its heredity a protein synthesis. Nucleotides themselves have 3 major components. These are; phosphoric acid, pentose sugar and an organic base. Within the organic base there are 5 different bases that are divided into 2 groups. The first groups are referred to as pyrimidines and are a single ring with six sides. The second groups are known as purines and have two rings with six and five sided rings. The purines and pyrimidines are bonded together through chemically.

The two acids that are especially important are the RNA and DNA. They play the most important role in protein synthesis and heredity.  RNA is the single strand of nucleotides and there are 3 different forms of RNA within the body; Ribosomal RNA, Transfer RNA and Messenger RNA. Whereas, DNA is a double stranded of nucleotides. Each cell within the body has the same amount of DNA within them and instructions are stored within it so that it can be replicated and constructed into new cells.

The construction of new cell is a process that happens continuously throughout the body, leading to many new cells be created for numerous different functions.  These cells can range in form and function. Embryonic stem cells for instance, can differentiate into most cell types which is why they are considered pluripotent.  Other pluripotent cells can be taken from the embryonic stem cells.  They are derived from 4-5 day old embryos of the human body. As the embryos develop into zygotes which then divides until it becomes a blastocyst. This is because embryonic stem cells that are able to be used are the inner mass of the embryo blast.  This is because stem cells are able to divide and become different type of cells in special controlled cultures. They divide and replicate themselves without differentiation which all the other cells cannot.

Interphase is an integral part of the cell cycle. This is the sequence every cell goes through when it divides. It is broken into two parts; interphase and mitosis.  Interphase have different phases within its process, G1 is the first growth phrase which is the cell division, S phase follows the G1 phase and is the syntheses stage. G2 then follows them both and is the second growth period.

The G1 phase is where most of the organelle is grown. Within S, DNA is copied and replicated and in G2 is when the centrioles replicate themselves. Interphase is commonly known as the resting phase however, it is a time of great activity. It is called the resting phase because of the invisible chromosomes. Some cells will remain in the interphase for many months due to the inability to divide.

Moreover, there are two factors which initiate and/or stimulate cell division to begin. These are physical and chemical.

Physical factors need to be attached to the tissue to divide. There are also the density dependent factors where cells stop growing because of nutrients. However, there are more chemical factors that impact cell divisions than physical. These factors are nutrient availability and different growth factors such as P27 which regulates protein and blocks the entry of the S phase.

Daughter cell refers to newly formed cells from the existing parental cell. This is due to mitosis, which then ensures the cells will contain the exact same number of chromosomes of the parent cells. The number of chromosomes within the nucleus is called the diploid number and every cell has a diploid number except gametes. Gametes only have half the number of diploid but this number is restored when the gametes are fertilized.

Mitosis is the sequence that is broken four stages; prophase, metaphase, anaphase and telophase. Within Prophase, chromosomes become collided threaded. Within earlier stages of prophase the chromosomes become thicker and shorter and can be replicated, however, in later stages the nuclear membrane breaks down and disappears. Each chromosome consists of two structures called chromatids which are joined together by centromeres. Then within metaphase, the spindle becomes formed and the chromosomes are lined within the middle of the spindle. Once again the chromatids are attached by the centroemere. Moving onto the anaphase the pairs of chromatids are then removed by movement of fibers. Which then move in opposite directions of each other. These newly separated chromatids are known as chromosomes. Lastly, within the telophase both the chromosomes and chromatids finally reach the spindle. They will begin to uncoil and will become invisible again. The Spindles will begin to differentiate and a nucleus will reform in each nucleus. This means that each new structure will contain a copy of the DNA, meaning it can now being to replicate itself. This happens due to cytokinesis and each new cell is genetically identical daughter cells.

Cancer cells at the very core are damaged versions of normal cells. They continue to grow until they begin to damage the healthy cells of the body. Whilst, they have the ability to spread rapidly over large areas, they do not have the immunity that normal cells do. As mentioned they are damaged versions of normal cells and therefore they all begin with a cell. Normally, within the body there is around thirty trillion cells, however when there is faulty signal within the cells, a cell may begin to grow and multiply beyond control. This leads to a tumor being formed, also known as a primary tumor. This can lead to secondary tumors being formed. Cancer then begins to grow and develop due to changes within the genes of cells, these changes are called mutations.

Mutation may be caused by the normal instructions for division of cells not being fully understood and so the necessary control of the process is lost or interrupted.

Discussion

Stem cells have three main properties, which were briefly mentioned within the introduction. These were: 1) they are capable of dividing and renewing themselves; 2) they are unspecialized; and 3) they can give rise to specialized cell types. Unlike other cells such as, nerve cells or blood cells, stem cells can replicate themselves many times over. This is also called to proliferate. A starting population of stem cells that proliferates can result in millions of cells. If these cells stay unspecialized. They are capable of long term self renewal. The specific reasons that allow stem cells to remain unspecialized remain unknown to scientists.

One of the properties of stem cells is that they do not have specific structures that allow them to perform specific functions. This can lead to a rise of specialized cells. This rise is called differentiation, within this process the cells go through different stages, becoming more specialized at each stage. Adult stem cells are undifferentiated cells derived from the body (Stem Cells Basics 2015). Stem cells, as mentioned above have the ability to become more than one type of cell within their development. Whereas, differentiated cells can only become one type of cells. While both undergo mitosis, stem cells have the ability to become any cell type. Differentiation occurs when the zygote develops into a more complex multi-cellur state. As the differentiation occurs, the cells cell acquires a specific function that cannot change.

To summarize, stem cells are the most versatile cells within the body. Whilst, all cells have instructions and function within them. They are distinguished by two important characteristics. These characteristics allow the cells to become different cells from division or remain stem cells.

Regarding cells, the differences between them can be found in minuscule ways, from cancer cells to viruses. These small differences that occur through mutations or the host cell being infected. Research into these cells has become more solid within the last decade, however, further research into the creation of cancer cells and virus cells and how the differ from normal cells must continue.

Conclusion

In summary, research into stem cells has become more solid however; there are still areas that need to be explored. Specifically, the ability that allows stem cells to remain unspecialized is still unknown.  Further research should examine the differentiated of cancer cells and viruses as research is too broad at this current time.

References

 

Appendices

Appendices 1-

2 –

3 –

Similarities

Prokaryotic cells

Eukaryotic cells

Nucleus

DNA is found within the nucleus of the cell.

 Division happens via mitosis.

Nucleus is known as a nucleoid which is not a true nucleus. (Wiley & Sons, 2014).

DNA is more complex.

It is found within the middle of the cell and holds the DNA together.

Division happens via meiosis.

Ribosome

Responsible for making protein within the cytoplasm. Smaller than Eukaryotic

Bigger than in Prokaryotic cells.

Cytoplasm

Liquid material that contains DNA and other parts of the cell to function.

DNA contained within the nucleus is in the cytoplasm outside the nucleus.

Differences

Chloroplasts

Only found within plant or algae cells which are eukaryotic

Only found in eukaryotic cells and are responsible for extracting food from the sun and CO2.

Golgi apparatus

This is not found as the cell is not as complex as a eukaryotic cell.

Materials are transported through the cytoplasm

Mitochondria

Respiration takes place within the mesosome. ATP is not required within prokaryotic cells. As they can use passive transport.

Respiration takes place and ATP is produces creating energy for cell reactions.

Rough and smooth endoplasmic reticulum

Does not produce lipids.

Smooth endoplasmic adds carbohydrates and proteins and produces lipids. Rough is responsible for synthesizing proteins needed for the cells and environment around the cells.

4 –

Organelle

Function

Factory part

Nucleus

DNA Storage

Room where the instructions are kept

Mitochondrion

Energy production

Power plant

Smooth Endoplasmic Reticulum (SER)

Lipid production;

Detoxification

Accessory production

Rough Endoplasmic Reticulum (RER)

Protein production

Primary production line

Golgi apparatus

Protein modification

Shipping department

Peroxisome

Lipid destruction

Waste removal

Lysosome

Protein destruction

Recycling

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