The eukaryotic cells are very different indeed. Not only have they got a cell membrane, a cell wall, cilia and flagella, it also has a battery of organelles inside which each have their own special jobs according to what the specific cells function is.
For example if you take the sperm cell in the male reproductive system, (pictured below in fig1) it has a long distance to travel and then when it finally gets there it has to try and fertilise the female egg. Inside the sperm there is nucleus, this is the most prominent part and could be called its epicentre of any cell as it controls everything the cell does like the synthesis of the protein in the nuclear Deoxyribonucleic acid (DNA), the making of ribosomes in the Ribonucleic acid (RNA) and even cell division. It also contains the cells chromosomes.3 The second part of the sperm cell is the mid section where the mitochondria are, these are the cells energy stores. Sperm cells contain a high number of mitochondria because they have a long journey to fertilise the egg.5 The mitochondria is found in both plant and animal cells they are a form of energy or adenosine triphosphate (ATP) and contain their own DNA they are rod shaped and found in the cells cytoplasm.3 The final part of the sperm cell is the tail also known as the flagella (this is also found in the bacteria cell) this helps the sperm with movement on its journey to the egg.
The red blood cells (RBC) are very different indeed unlike most plant and animal cells they have no nucleus when fully matured and no organelles except their plasma membrane and they are formed in the bone marrow.3 They contain haemoglobin which is a protein designed to carry oxygen through the body. The RBC also removes carbon dioxide (CO2) from the body. These specialist cells are circular biconcave (round and flat) in shape (as shown below in fig 2) this gives them a much greater surface area to exchange oxygen and carbon dioxide in the lungs and with body cells.
White blood cells (WBC) on the other hand have a true nucleus and contain lysosomes these are found in both plant and animal cells. WBC is the bodies fighting mechanism against infections, it break down bacteria through a process called phagocytosis this is where the white blood cells attack the bacteria invading and draws it into the cell by surrounding it with false arms and then the lysosomes inside the WBC take over.3 Lysosomes are the organelles that chemically digest the bacteria once the white blood cells have engulfed it. They are responsible for the digestion or waste disposal in the cell of things like bacteria and foreign bodies as well as unwanted organelles. Basically they clean up anything unwanted and get rid of it. (As shown in fig 3.)
The liver in the animal is one of the hardest working parts of the body. The cells in this area are secreating cells which mean the have to work hard to get rid of alot of toxins and make other substances safe to pass on to other organs either for the body to use or to the kidneys to pass out as urine. These cells have a large amount of an organelle called the smooth endoplasmic reticulum (SER). This is where the fatty acids or lipids are synthesized for example this is where the alcohol and drugs would be removed from the bloodstream.2 When the substance or toxin is going to be secreted from the cell the SER pass them to the Golgi apparatus. The Golgi apparatus is present in both plant and animal cells. This is where the materials made in the ERs are packaged for export to other parts of the cell or for excretion. The Golgi is quite a large part of the cell which was probably why it was one of the 1st organelle discovered.6
The plant cell although it is a eukaryotic cell like the animal cell is somewhat different it has some organelles inside but it has a cell membrane and a cell wall this help’s the plant keep its shape like in the bacteria cell.(as shown in figure 4) Inside the plant cell there is a large vacuole, this is an organelle only present in the plant cell and normally takes up most of the inside of the cell.7 Its functions are storage of waste, water and nutrients. It also has some digestive functions. Another organelle which is one only found in plant cells is the chloroplast these are filled with a substance called chlorophyll a green like colour.6 There are large amounts of these in plant cells as this is where the plant cell makes and stores its energy this is called photosynthesis. The plant cell uses the light from the sun and gets the carbon dioxide from the air around it through its leaves and gets water from its roots. The cell uses the energy of the Sun light to turn the water and carbon dioxide into carbohydrates (sugar) and oxygen. The sugar stays in the plant for stored energy and Oxygen leaves the plant through its leaves for humans to breathe.8
It is very clear to see that both the prokaryotic and eukaryotic cells are unique in their own way, but there is something even more unique about the individual cells within the two types, weather it is plant animal or bacteria. When a cell has a particular function the structure inside plays a large part, a particular organelles inside the cell that promotes the job the cell does appears to exist in a larger amount to help the cell function and get the job done to the best of its ability. Whether it is for protection on the outside with the cell wall and cilia in the bacteria cell, energy in the sperm cell with the mitochondria and the flagella for movement, no organelles at all in the red blood cell to have a larger surface area to enable carrying large amounts of oxygen, lysosomes in the white blood cell for digestion of waste, SER, the Golgi apparatus and the vesicles in the liver cell to remove waste and secrete, and in the plant cell it is the vacuole and the chloroplast for the energy stores and the photosynthesis. Therefore if each of these cells did not have these organelles in their structure they would not be able to function in the way they are needed to.
- Daniel, S. Biology: A self teaching guide 2nd edition (2002)
Wiley Publishers. ISBN 978-0471223306
- Scogna, K. (2004) The Gale Encyclopaedia of science Vol 1 3rd edition. Cells.
- Toole, G&S. New understanding Biology for advanced level 4th edition. (1999) Nelson Thorne’s Ltd Cheltenham UK. ISBN:978-0-7487-3957-8
- University of Leeds. Medical microbiology- A brief introduction. John Heritage (2004-2006) Downloaded 27/11/1.
- The Florida state university. Molecular expressions. Cell biology and microscopic structure and function of cells and viruses. Michael. W. Davidson (1995-2010)
- Beckett, B S. Biology: A modern introduction. G.c.s.e edition (1986) OUP Oxford. ISBN: 978-0199142606
- Cohen, N. Cell structure function and metabolism (1991) Hodder &Stoughton, London UK ISBN: 9=780340-531884
- Cox, J. (2011) Horticulture Vol. 108 issue 6. Plants in Candy land.
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The punctuation, grammar and spelling are all fine. The referencing is presented neatly but the candidate could use a proper referencing technique next time for it to look more professional.
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The candidate explains the different types of cells and the functions of the different parts to a very high level. The information is displayed well in an essay format and all the information synthesised so that the candidate is not just providing continuous lists of the functions of each cell organelle. The candidate gives examples of specialised cells and explains well how they differ from normal cells hence enabling them to become adapted to their function. The candidate also uses images to help convey the meaning of their text.
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The candidate responds very well to the question and this piece is done to an high level. Whilst the candidate could provide greater scientific depth to get greater marks, the range of information used and the way it is presented and easy to read shows a very high level for this qualification. The conclusion is well rounded and adequate.