Biochemistry of RBCs

Question 1

Where does oxygen bind on RBCs?

Answer 1

Haem pocket

Question 2

Describe the allosteric effect of haem

Answer 2

As one O2 binds, it alters the binding affinity for the next O2 hence sigmoid shaped curve

Question 3

What can get in between chains and change O2 affinity - so less is bound (i.e. more is released) at the same PO2?

Answer 3

2,3 DPG

Question 4

What types of haemoglobin bind O2 more readily?

Answer 4

At same PO2, HbF and myoglobin bind more O2

Question 5

What is the critical part of the O2 affinity curve?

Answer 5

5.3 (venous) to 13.3 (arterial) partial pressures

Explains how O2 is transferred to fetus in utero and to muscles

Question 6

When would the O2 binding curve be shifted right?

Answer 6

By molecules that interact with Hb (H+, CO2, 2,3 DPG)

This results in more O2 being delivered to tissues

Think of why CO2 and H+ may be increased, good to have more O2 around in these conditions

Question 7

What are key facts about red cell structure?

Answer 7

Question 8

Why do RBCs need a large surface area / volume ratio’?

Answer 8

Question 9

What is the Embden-Myerhof pathway?

Answer 9

Anaerobic glycolysis pathway generates ATP (energy) and NADH (reverses Fe+++ (metHb) to Fe++(Hb))

Question 10

What is the hexose monophosphate shunt (or pentose phosphate pathway)?

Answer 10

Generates NADPH -protects against oxidative stress, regenerates glutathione a key protective molecule

Question 11

What is the rapapoport-Lubering shunt?

Answer 11

Generates 2,3 DPG that right shifts oxygen disassociation curve and allows more oxygen to be released

Question 12

Hb with oxidised Fe3+ is called? It can’t carry oxygen

Answer 12

Methemoglobin (MetHb)