Carbohydrate (Part-I)

Introduction: In contrast to protein and lipid, carbohydrates are mainly been utilized to provide as a source of energy to run life activities. Plants are the primary producers of carbohydrate by utililyzing atmospheric CO₂, H₂O and sunlight. Carbohydrate are present in very simple as monosaccharides to complex form as polysaccharides and glycoconjugates. In the present chapter, we will discuss salient features of carbohydrates, its structure and metabolism in animal system.   

Monosaccharides: it is simplest carbohydrate, aldehyde or ketone with two or more hydroxyl group. The backbone is madeup of 3 to 6 carbon with hydroxyl group attached to it. These simple sugar are named by the number of carbonpresent in each molecule; triose with 3 carbon such as glyceraldehyde; tetrose with 4 carbon such as erythrose, threose; pentose with 5 carbon such as ribose, arabinose, xylose, lyxose; hexose with 6 carbon, such as glucose, fructose etc (Figure 36.1). These carbon atoms are chiral centre to give stereoisomeric sugar found in nature. In addition, reaction between first carbonyl group and the fifth carbon gives cyclic form of sugar. The cyclization generates additional chiral centre and contribute into stereochemical complexicity of the molecule (Figure 36.2).

  

Figure 36.1: Different forms of monosaccharides.