Question

(a) Describe the ways of classifying amino acids and give example of each class.


(b) What are the structural and functional differences between myoglobin and haemoglobin?

Answer 1

(a) Amino acids are classified in different ways according to their structure and properties. In general, they can be divided into six groups according to their side chains:

• Aliphatic (i.e., glycine, alanine)
• Hydroxyl- and sulfur-containing (i.e., serine, cysteine)
• Cyclic (proline)
• Aromatic (i.e., tyrosine)
• Basic (Histidine, arginine, lysine)
• Acidic (Aspartate, glutamate)

(b) Hemoglobin consists of four polypeptide chains, whereas myoglobin is a protein consisting of a single subunit. Hemoglobin is an oxygen-transporting protein, while myoglobin is an oxygen-storing protein. Hemoglobin can be found in erythrocytes, whereas myoglobin is located in muscle fibers.