Describe the similarities and differences between haemoglobin and collagen.

Similarities:Both have a quaternary structure (consisting of more than one polypeptide).Both are found in animals (haemoglobin is found in blood and collagen is found in the muscles, skin, bones and tendons).
Differences:Haemoglobin consists of four polypeptides while collagen has three.Two types of polypeptides occur in haemoglobin (alpha and beta chains) whereas in collagen all three polypeptides are identical. Haemoglobin is globular and has a tertiary structure while collagen is fibrous and lacks a tertiary structure.Haemoglobin is conjugated (contains heme groups - example of a prosthetic group) whereas collagen is not conjugated. Haemoglobin has a functional role (carries oxygen) while collagen has a structural role.