Haemoglobin

Question 1

Hb has a high what for oxygen?

Answer 1

High affinity for oxygen - each molecule can carry 4 oxygen molecules

Question 2

Hb joins oxygen in the lungs to form what?

Answer 2

Oxyhaemoglobin - this is reversible, when oxygen dissociates from oxyhemoglobin near body cells it turns back into Hb

Question 3

What is partial pressure of oxygen (pO2)?

Answer 3

A measure of oxygen cocentration

Question 4

How does Hb’s affinity for oxygen vary on the pO2?

Answer 4

Oxygen loads onto Hb to form oxyHb where there’s a high pO2. OxyHb unloads its oxygen where there’s a low pO2

Question 5

What does a dissociation curve show?

Answer 5

How saturated the Hb is with oxygen at any given partial pressure

Question 6

Why is a dissociation curve S-shaped?

Answer 6

When Hb combines with the first O2 its shape alters to make it easier for other molecules to join. As the Hb becomes saturated it gets harder for O2 molecules to join. So, the curve has a steep bit in the middle where it’s easy for O2 to join, and shallow bits at each end where it’s harder

Question 7

Explain the Bohr effect

Answer 7

1. When cells respire they produce carbon dioxide, which raises the pCO2
2. This increases the rate of oxygen unloading - so they dissociation curve shifts right
3. The saturation of blood with oxygen is lower for a given pO2, meaning that more oxygen is being released