2.2 Organic Compounds

Many chemical compounds in living organisms are known as organic compounds' which contain C,H and O. In the earlier chapter we have seen that an organism is formed primarily from six elements: C, H, O, N, P, Ca. The study of organic compounds is called organic chemistry.

(A) Carbohydrates

There are plenty of organic compounds present in nature. All living things contain basically four types of organic compounds.Carbohydrates form the first category of organic compounds.

For metabolism the organism requires energy. This energy is provided primarily by carbohydrates. Carbohydrates are basically composed of 3 elements, C, H, and O. The ratio of H to O is 2:1, as in a water molecule (H₂O). There are types of carbohydrates according to the complexity of the carbohydrate molecule. Carbohydrates and usually taste sweet to humans are referred to as sugar. If a carbohydrate is made up from a single molecule it is called monosaccharide. When the carbohydrate is made up of 2 sugar molecules linked together it is referred to as a adisaccharide Carbohydrates which have more than 3 molecules are called polysaccharides. The general formula to represent the carbohydrate is Cx(H₂O)y.

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Table I : Schematic Representation of Carbohydrates

1) Monosaccharides

They are the simplest soluble sugar. Depending on the number of carbon atoms present, monosaccharides are further classified as:

a) trioses ® (3 carbons) C₃H₆O₃ e.g. glyceraldehyde

b) pentoses ® (5 carbons) C₅H₁₀O₅ e.g. ribose and deoxyribose

c) hexoses ® (6 carbons) C₆H₁₂O₆ e.g. glucose

Glucose C₆H₁₂O₆ is a basic form of fuel in all living things. It is soluble in blood plasma and water and so it is transported by body fluids to all cells in the body. In cells it is metabolized and releases energy. Glucose is also the main product of photosynthesis and also an initiating material for cellular respiration.

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