Transport of Oxygen by Haemoglobin

Question 1

What do we mean by ‘partial pressure’ of oxygen?

Answer 1

concentration of oxygen

Question 2

What does the oxygen dissociation curve show?

Answer 2

relationship between saturation of haemoglobin with oxygen abd the partial pressure of oxygen

Question 3

Explain why the gradient of the oxygen dissociation curve is shallow initially

Answer 3

shape of haemoglobin makes it difficult for first oxygen to bind so at low oxygen partial pressures little oxygen binds

Question 4

Explain why the gradient of the oxygen dissociation curve steepens after the first molecule of oxygen has bound

Answer 4

binding of the first oxygen changes the quaternary structure of haemoglobin making it easier for subsequent oxygen molecules to bind.

Question 5

What is positive cooperativity?

Answer 5

when the binding of the first molecule makes binding of the second easier. It takes a smaller increase in partial pressure of oxygen to bind the second oxygen compared with the first.

Question 6

Explain why the gradient of the oxygen dissociation curve flattens off after the thrid oxygen has bound.

Answer 6

with the majority of binding sites occupied it is less likely that a single oxygen molecule will find an empty site to bind to

Question 7

Where on the oxygen dissociation curve do we find haemoglobin with a greater affinity for oxygen (loads easily, unnloads less easily)

Answer 7

to the left

Question 8

Where on the oxygen dissociation curve do we find haemoglobin with a lower affinity for oxygen (loads less easily, unnloads easily)

Answer 8

to the right

Question 9

What happens to haemoglobins affinity for oxygen in the presence of carbon dioxide?

Answer 9

affinity is reduced

Question 10

What is the bohr effect?

Answer 10

the greater the concentration of carbon dioxide the more readily haemoglobin releases oxygen

Question 11

Describe the affinity for oxygen of haemoglobin at low carbon dioxide, high oxygen partial pressures (ie in lungs)

Answer 11

high affinity

Question 12

Describe the affinity for oxygen of haemoglobin at high carbon dioxide, low oxygen partial pressures (ie respiring tissues)

Answer 12

low affinity

Question 13

Explain how high carbon dioxide reduces the affinity of haemoglobin to oxygen

Answer 13

dissolved carbon dioxide is acidic causing haemoglobin to change shape