The Bohr effect, myoglobin and altitude

Overview

Shift of the dissociation curve to the right, physiological advantage of the Bohr effect to a hard-working muscle and why athletes train at high altitude before an important competition.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   State what the Bohr effect is.

   Model answer

   The Bohr effect is the shift of the oxygen dissociation curve to the right caused by a rise in the partial pressure of carbon dioxide, a rise in temperature or a fall in pH.

2. 2

   What does a shift of the dissociation curve to the right mean for the saturation of haemoglobin?

   Model answer

   At any given partial pressure of oxygen the haemoglobin is less saturated, so more oxygen has been released.

3. 3

   Explain how a fall in pH affects the release of oxygen from haemoglobin.

   Model answer

   A lower pH reduces the affinity of haemoglobin for oxygen, so oxygen dissociates from it more readily.

4. 4

   How does a rise in temperature affect the dissociation of oxygen from haemoglobin?

   Model answer

   A higher temperature lowers the affinity of haemoglobin for oxygen, so more oxygen is released at any given partial pressure.

5. 5

   Explain the physiological advantage of the Bohr effect to a hard-working muscle.

   Model answer

   The muscle is producing extra carbon dioxide and heat, which shift the curve to the right, so haemoglobin passing through it delivers more oxygen exactly where the demand is greatest.

6. 6

   Why does the Bohr effect not reduce the amount of oxygen picked up in the lungs?

   Model answer

   Carbon dioxide is excreted at the alveoli, so the partial pressure of carbon dioxide there is low and haemoglobin still saturates almost fully.

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