2. Haemoglobin

role of Haemoglobin

Carry oxygen around the body.

Describe the structure of haemoglobin

• Large protein with a quaternary structure.

• Made up of 4 polypeptide chains.

• Each chain has a haem group which contains an iron ion and give haemoglobin its red colour.

• Each molecule of human haemoglobin can carry four oxygen molecules.

loading

unloading

association

dissociation

Affinity for oxygen meaning

The tendency a molecule has to bind with oxygen.

Depends on pO2.

pO2

A measure of oxygen concentration

As pO2 increases, haemoglobin’s affinity for oxygen ….

increases

1. Where does oxygen load onto haemoglobin?

2. Where does oxygen unload from the haemoglobin,

1. Where there’s high pO2.

2. Where there’s low pO2.

dissociation curve

Shows how saturated the haemoglobin is with oxygen at any given partial pressure.

Why is the curve an s on a dissociation curve

1. When first O2 bonds, the shape of the haemoglobin alters, making it easier for other O2 molecules to bond.

2. However, as the haem groups get filled, it makes it harder for other O2 molecules to bond.

pCO2

a measure of the concentration of CO2 in a cell.

How does pCO2 affect the loading and unloading of oxygen.

• Haemoglobin gives up oxygen more readily at a higher pCO2.

What does increasing the PCO2 do to the curve on the dissociation curve?

shift to the right.

where would you find high affinity haemoglobin?

low oxygen environments

who would have low affinity haemoglobin?

• organisms with high activity levels.

• Organisms that are small in size, as they need a higher metabolic rate to keep warm.

How does size affect the type of haemoglobin?

animals that are smaller have a larger SA:V and so lose heat more quickly and therefore need a higher metabolic rate and therefor a low affinity haemoglobin.