Compare and contrast polypeptide with polysaccharide

Firstly, when we are comparing with polypeptide and polysaccharide, we can find that both of them are polymers and also formed by condensation reaction. Many monosaccharides are combined by glycosidic bond to give a polysaccharide which structure can be branched or straight. And a large number of amino acid molecules joined together by peptide bonds form a polypeptide.

However, monosaccharide which is made up of carbon, hydrogen and oxygen and the ratio of hydrogen: oxygen is 2:1 while amino acid is made up of carbon, hydrogen, oxygen, nitrogen with sulphur but there are no particular ratio. Moreover, each monomer of carbohydrate is a ring structure and has OH- and H+, and CH2OH group join to a carbon atom while each amino acid has amino NH2 group and a carboxyl COOH group.

Furthermore, there are 20 essential amino acids due to different R groups The R groups affect the polarity and hydrophobicity of the protein molecules while the size of the polysaccharide molecule makes them insoluble or slightly soluble in water, thus, they exert no osmotic influence.

In addition, the primary structure of protein is due to different sequence of 20 different amino acids, which give rise to different protein, there is no fix ratio of any amino acids in a protein molecule.

Lastly, protein can act as an enzyme but carbohydrate cannot, because enzyme serve as organic catalyst in lowering the activation energy in a chemical reaction, thus accelerate the rate of reaction, also, carbohydrates do not have a specific configuration for providing active sites. So, they cannot serve as enzyme.

6S Choi Ngor Shing