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The Importance and Biological Functions of Carbohydrates.

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The Importance and Biological Functions of Carbohydrates. Carbohydrates have many functions. This essay will look at some of them and also what carbohydrates are constructed of. A Carbohydrate molecule contains Carbon, Hydrogen and Oxygen. There are twice as many Hydrogens as there are Oxygens, the same proportion as water. Carbohydrates have the general formula of C (H O) Carbohydrates can be divided into three main types. These are monosaccharides (single sugar units), disaccharides (two sugar units) and polysaccharides (many sugar units). Different monosaccharides contain different numbers of carbon atoms. Trioses contain three, pentoses contain five and hexoses six. Carbohydrates have many different functions and come in many different forms. Ribose and Deoxyribose are both pentose monosaccharides and are found in RNA and DNA. Glucose and Fructose are both hexose monosaccharides. Glucose is an important source of energy in respiration and Fructose is found in fruits. Sucrose is a disaccharide formed from Glucose and fructose. It is the form in which carbohydrates are transported in plants. Maltose is a disaccharide of glucose and is formed from the digestion of starch. The carbohydrate in milk is lactose and it is formed from Glucose and galactose. ...read more.


A plant cell wall has high tensile strength because of the structure of cellulose. It consists of long straight chains that are linked together by hydrogen bonds. The bundles are called microfibrils. These are held together in fibres and the plant cell walls are made up of fibres running in different directions. This is what gives the high tensile strength. Carbohydrates have six main functions in the body: 1. Providing energy 2. Sparing the use of proteins for energy 3. Breakdown of fatty acids and preventing ketosis 4. Biological recognition processes 5. Flavour and Sweeteners 6. Dietary fibre. Glucose is the only sugar used by the body to provide energy for its tissues. Therefore, all digestible polysaccharides, disaccharides and monosaccharides must eventually be converted into glucose or a metabolite of glucose by various liver enzymes. Because glucose is so important to the body, blood glucose levels must be kept fairly constant. The liver is the organ that regulates blood glucose level. When food is consumed, pancreatic beta cells sense the rise in blood glucose and begin to secrete insulin. In the liver, insulin causes the uptake of glucose as well as the synthesis of glycogen, a glucose storage polymer. ...read more.


Soluble dietary fibres like pectin and mucilage pass undigested through the small intestine and are degraded into fatty acids. These can be used as a fuel by the large intestine. In general, the consumption of soluble and insoluble fibre makes the elimination of waste much easier. Since dietary fibre is both indigestible and an attractant of water, stools become large and soft. As a result, faeces can be expelled with less pressure. A high fibre diet can prevent intestinal disease as well as reduce the risk of developing obesity by increasing the bulk of the meal without yielding much energy. An expanded stomach leads to satisfaction despite the fact that caloric intake has decreased. Carbohydrates not only serve nutritional functions but are also thought to play important roles in cellular recognition processes. For example, many antibodies and peptide hormones contain glycoprotein sequences. During the course of many hours or days, the carbohydrate polymer linked to the rest of the protein may be cleaved by circulating enzymes or be degraded spontaneously. The liver can recognise differences in length and may internalise the protein in order to begin its own degradation. In this way, carbohydrates may mark the passage of time for proteins. It is clear that carbohydrates do have many functions and that they are biologically very important because they do such varied and important jobs. ...read more.

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Response to the question

Good introduction - You mentioned where ribose and deoxyribose are found in the cell (RNA and DNA), so I would also add where glucose and fructose are found in the cell (namely in glycolysis pathways, in polymers, in glycoproteins etc)

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Response to the question

Good introduction - You mentioned where ribose and deoxyribose are found in the cell (RNA and DNA), so I would also add where glucose and fructose are found in the cell (namely in glycolysis pathways, in polymers, in glycoproteins etc)

Level of analysis

Organisation - Headings would help with the organisation of the essay, especially when you are listing all the different common sugars, having a heading such as “Examples of common sugars” would make it a lot clearer what you are trying to say.
Instead of listing the carbohydrates and what they are made up, compare them together to say the similarities and differences, and give details. For example, “Cellulose and starch are both made up of d-glucose, but glucose in cellulose is linked by a β(1→4) linkage, whereas in starch it is α(1→4) linkage instead.”
You mentioned the six main functions in the body, so headings for each of the headings would be appropriate.

Quality of writing

Other remarks - Another improvement would be to use scientifically common terms, so instead of saying “Carbon number one” write “C1”
Good use of diagrams to visualise molecules
Reading the essay back to yourself would help it flow better
There are a lot of accurate and concise details, this shows good understanding. Ketosis was definitely undergraduate stuff, and it seems like you understood it.
Putting the importance of dietary fibres into context of intestinal disease is great, this really answers the question.
Having references to back up your points would make this an even better essay.

Overall, this is a good essay, showing real understanding and extra knowledge.

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Reviewed by superwiseman 01/03/2012

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