Haemoglobin and oxygen dissociation curves

Question 1

Describe the structure of haemoglobin

Answer 1

Globular protein.
Quaternary structure - consists of 4 polypeptide chains.
Each polypeptide contains a haem group.

Question 2

Describe the role of haemoglobin

Answer 2

Found in red blood cells.
Binds to oxygen to form oxyhaemoglobin
Carries oxygen around the body to the respiring tissues.

Question 3

How does the partial pressure of carbon dioxide affect the binding of oxygen to haemoglobin?

Answer 3

Carbon dioxide dissolves in blood plasma to form (carbonic) acid.
Causes the pH to drop.
Haemoglobin changes shape slightly.
Affinity for oxygen decreases.
More oxygen is released from the haemoglobin.
Know as the Bohr effect

Question 4

Why does oxygen binds to haemoglobin in the lungs?

Answer 4

Partial pressure of oxygen is high
Haemoglobin has a high affinity for oxygen.
Oxygen diffuses into the red blood cell and binds to haemoglobin

Question 5

Why is oxygen released from the haemoglobin in respiring tissues?

Answer 5

Partial pressure of oxygen is low.
Partial pressure of carbon dioxide is high due to respiring tissues
Affinity for oxygen decreases
Oxygen is released to the respiring tissues.

Question 6

People living at high altitudes have more red blood cells than people living at sea level. Explain the advantage of this.

Answer 6

Partial pressure of oxygen is lower in the air.
More red blood cells
More haemoglobin
Carry more oxygen to tissues

Question 7

During exercise the oxygen dissociation cure moves to the right. Explain the advantage of this.

Answer 7

Haemoglobin releases more oxygen to the muscles.

Aerobic respiration maintained releasing more energy for muscle contraction

Question 8

Describe how haemoglobin loads and unloads oxygen in the body

Answer 8

Haemoglobin picks up oxygen at high partial pressure eg in the lungs
Haemoglobin unloads oxygen at low partial pressures eg in respiring tissues

Question 9

What is cooperative binding in haemoglobin?

Answer 9

Difficult for the first oxygen molecule to bind to haemoglobin.
Binding of first oxygen changes the tertiary structure of the haemoglobin
The position of the haem groups shift and allows the next two oxygen molecules to bind more easily.