Oxygen Transport

Oxygen Transport

Oxygen is carried around the body in red blood cells.

Red blood cells contain the molecule haemoglobin which joins with oxygen to make oxyhaemoglobin.

Haemoglobin + oxygen oxyhaemoglobin

Oxygen Transport

Haemoglobin is globular protein which is made up of 4 peptide chains, each chain contains one haem (iron) group.

Each haem group can combine with one oxygen molecule (O2).

This can be summarised as:

Hb + 4O2 Hb(O2)4

Note – this is a reversible reaction

Oxygen Transport

Each red blood cell carries millions of haemoglobin molecules. That’s a lot of oxygen!

Oxygen saturation is the amount of oxygen bound to the haemoglobin in our blood, expressed as a percentage of the maximum.

The units are SaO2%. Blood leaving the lungs normally has a saturation of 95-99%.

100% saturation – means the haemoglobin is carrying its maximum amount of oxygen

50% saturation – it is only carrying half of what it could carry.

Oxygen TransportAn experiment was carried out to measure the saturation of blood with oxygen at different concentrations of oxygen.

You have the results of this experiment and need to plot the graph.

In this experiment the concentration of oxygen was measured as a partial pressure.

Oxygen TransportIn this experiment the concentration of oxygen was measured as a partial pressure.

Partial pressures can create diffusion gradients – gases move according to the concentrations.

Eg – in the lungs the partial pressure of oxygen is 13.3kPa, in the blood it is about 5.3kPa. What does this mean in terms of diffusion?

Oxygen Transport

This is called the oxygen dissociation curve.

Oxygen Transport1. Where on your graph is the haemoglobin fully saturated

with oxygen?

2. Where on the graph will oxygen be released?

3. Where on the graph will oxyhaemoglobin dissociate into oxygen and haemoglobin?

4. Where on the graph will the blood be bright red?

5. Where on the graph will the blood be if it is from a vein?

6. Where on the graph represents blood leaving a muscle?

7. Where on the graph represents blood leaving the lungs?

Oxygen Transport

The oxygen dissociation curve can also be affected by levels of carbon dioxide in the blood. Remember levels of carbon dioxide go up when rates of respiration increase.

Carbon dioxide dissolves in the blood to form carbonic acid.

This change in blood pH affects the haemoglobin in the red blood cells causing them to lose their oxygen more readily.

This is known as the Bohr effect.

Oxygen Transport

The Bohr Effect