The Oxygen Dissociation Curve | The Bohr Effect

How is haemoglobin structured

It contains 4 haem groups linked to 4 polypeptide chains
Each haem group contains an iron atom
This haem group can combine with one O2 molecule to form oxyhaemoglobin

What is the oxygen dissociation curve

A curve that shows how the percentage of oxygen saturation of the blood changes as the availability of oxygen changes

What is the shape of the oxygen dissociation curve

An S shaped curve

Explain the Oxygen Dissociation Curve

Initially the oxygen binds slowly to haem

When they bind, this causes a change in haemoglobin’s shape

Each change allows for a faster uptake of subsequent oxygen molecules (this is called the Allosteric Effect)

When oxygen is being released the first molecule is released quickly but others more slowly

The last oxygen is only given up at very low partial pressures of oxygen

Therefore, as you move the the left of the curve, O2 saturation levels decrease

What is Myoglobin

A molecule similar in structure to haemoglobin in that it contains one haem group which allows it to transport one molecule of oxygen:

mb + O2 (reversible arrow) —→ mbO2

Features of Myoglobin

It has a higher affinity for oxygen and it only releases it after oxygen availability is low

What is the Bohr Effect

This is when the dissociation curve shifts to the right because carbon dioxide is in high concentrations

What is the effect of the Bohr effect of the release of oxygen from haemoglobin

The greater the amount of Carbon Dioxide present at respiring organs, the faster the release of oxygen from haemoglobin

How is Carbon Dioxide transported in the Bohr Effect

As carbonic acid (H2CO3) in solution or plasma
When it combines with the amine group of haemoglobin to form carbamino-haemoglobin
Hydrogen Carbonate when the carbonic acid dissociates into hydrogen carbonate and hydrogen ions