Hb

Question 1

Structure of protein

Answer 1

• Hb is a complex protein
• Consists of 4 sub units. Each has a polypeptide chain and a haem unit
• Each haem unit is an Fe2+ containing porphyrin derivative

• Each Hb molecule has 2 pairs of polypeptide chains
4 types of chains -alpha, beta, gamma, delta chains
Alpha chains – 141 a.a, Beta chains – 146 a.a

Question 2

2 Types of Hb seen in the adult

Answer 2

HbA – predominant form
- consists of 2 alpha and 2 beta chains
HbA2 – 2.5% , has 2 alpha and 2 delta chains

Question 3

• Type of Hb seen in fetus

Answer 3

HbF – consists of 2 alpha and 2 gamma chains
HbF is replaced by HbA soon after birth (beta chains are produced instead of gamma chains)
HbF has a higher affinity for oxygen compared to adult Hb
- Facilitates transfer of oxygen from maternal to fetal circulation
- It binds less to 2,3 – BPG compared to adult Hb