E&T: Haemoglobin

Question 1

Haemoglobin

Answer 1

Large protein with quaternary structure, with 4 chains each containing a haem group with an iron ion.

Question 2

Describe haemoglobins affinity for O2

Answer 2

High affinity - each molecule can carry 4 x oxygen

Question 3

Describe the reaction between oxygen and haemoglobin in the lungs:

Answer 3

Haemoglobin + oxygen <—> oxyhaemoglobin

Question 4

Partial pressure of oxygen (pO₂)

Answer 4

Measure of oxygen concentration

Greater concentration of dissolved oxygen = higher partial pressure

Question 5

When does oxygen load onto haemoglobin?

Answer 5

Where there’s a high pO₂

Question 6

What happens when there is a high pO₂?

Answer 6

Oxygen loads onto haemoglobin

Question 7

What happens when there is a low pO₂?

Answer 7

Oxyhaemoglobin unloads oxygen

Question 8

What is the pO₂ at the alveoli?

Answer 8

High - oxygen loads onto haemoglobin

Question 9

What happens when cells respire?

Answer 9

Use up oxygen - lowers pO₂

Allows red blood cells to deliver oxyhaemoglobin to respiring tissues

Question 10

Where pO₂ is high…

Answer 10

… haemoglobin has a high afinity for oxygen.

Question 11

Where pO₂ is low…

Answer 11

… haemoglobin has a low affinity for oxygen.

Question 12

Why is the dissociation curve ‘S-shaped’?

Answer 12

• When first O₂ molecule combines, shape of Hb changes.
• Makes it easier for more O₂ molecules to join = steep curve in middle.

Question 13

Affinity

Answer 13

Tendency to bind with oxygen

Question 14

How does a higher partial pressure of CO₂ affect haemoglobin?

Answer 14

Makes it give up oxygen more readily.

Question 15

Explain the Bohr effect:

Answer 15

• High concentration of CO2 causes oxyhaemoglobin curve to shift to the right
• Affinity for oxygen decreases because acidic CO2 changes shape of haemoglobin

Question 16

What does a higher pCO₂ do to the dissociation curve?

Answer 16

Shifts to the right as rate of oxygen unloading increases.

Question 17

How does living in a low concentration of oxygen affect affinity?

Answer 17

Higher affinity - dissociation curve shifts left.

Question 18

How does being active and have a high oxygen demand affect haemoglobin?

Answer 18

Lowers affinity - dissociation curve to the right.