Question

Choose the correct option(s) with regard to haemoglobin (Hb)

• A. Hb binds oxygen in a co-operative process
• B. The metal ion in oxy-Hb has a larger size than that in deoxy-Hb
• C. Hb takes up more oxygen at pH 7.4 than at pH 6.8
• D. The metal ion is paramagnetic in deoxy-Hb

Hint:

Deoxy-Hb: high spin Fe$^{2+}$ → paramagneticOxy-Hb: low spin Fe$^{2+}$ → diamagneticAlso remember Bohr effect for pH dependence

Answer 1

The Correct Option is A, C, D

Step 1: Binding.
Haemoglobin binds oxygen cooperatively, so statement A is correct.

Step 2: Metal size.
On binding oxygen the iron goes low spin and gets smaller, so statement B, which claims it grows, is wrong.

Step 3: pH and magnetism.
Higher pH raises oxygen affinity, so C is correct, and deoxy haemoglobin is paramagnetic, so D is correct.

Step 4: Answer.
\[ \boxed{\text{A, C and D}} \]