Haemoglobin (Mass transport in animals)

What is haemoglobin? (include information about its polypeptide chains)

• A protein with a quaternary structure

• Made up of 4 polypeptide chains (2 Beta and 2 Alpha)

How many O₂ molecules can haemoglobin bind to at once?

4

Define affinity of haemoglobin

The ability of haemoglobin to attract or bind to oxygen

Define saturated haemoglobin

When haemoglobin is holding the maximum amount of oxygen it can bind to

Define the loading/association of haemoglobin

The binding of oxygen to haemoglobin

Define the unloading/dissociation of haemoglobin

When oxygen detaches or unbinds from haemoglobin

Explain cooperative binding (2 points)

1. The haemoglobins tertiary and quaternary structure changes shape when the first oxygen binds

2. This makes it easier for further oxygens to bind

Describe the Bohr effect

1. A high pCO₂ increases acidity 

2. This changes the shape of haemoglobin slightly

3. The affinity of haemoglobin for oxygen decreases

4. This causes the curve to shift to the right

Describe 3 different oxygen environments organisms could live in

• Organisms from environment with continuously low pO₂

• Organisms who store oxygen for times when there is none

• Organisms with high metabolic rates

What do organisms from environment with continuously low pO₂:

• Require?

• What is their affinity of haemoglobin for oxygen?

• Need to gain full saturation of haemoglobin

• High affinity

Why are organisms from environment with a continuously low pO₂ curves shifted to the left?

• Higher affinity enables haemoglobin to become fully saturated at a low pO₂

• So respiring tissues can be supplied with enough O₂ for aerobic respiration

What do organisms who store oxygen for times when there is none:

• Require?

• What is their affinity of haemoglobin for oxygen?

• Need to store oxygen

• High affinity

Why are organisms who store oxygen for times when there is none curves shifted to the left?

• Higher affinity enables haemoglobin to remain associated with oxygen at a lower pO₂

• Oxyhaemoglobin dissociates when there pO₂ is very low

• To maintain aerobic respiration when oxygen cannot be obtained from the environment

What do organisms with high metabolic rates:

• Require?

• What is their affinity of haemoglobin for oxygen?

• Need high level of oxygen to be released to the tissues to maintain high rates of aerobic respiration

• Lower affinity

Why are organisms with high metabolic rates curves shifted to the right?

• Lower affinity means that small drops in pO₂ lead to rapid dissociation of oxyhaemoglobin

• So that large amounts of oxygen are released to tissues

• So high rates of aerobic respiration can take place

What is myoglobin?

A protein found in muscle tissues with the function of storing oxygen

Why is the myoglobin curve shifted to the left?

• Higher affinity enables myoglobin to remain associated with oxygen when there are small drops in pO₂

• Oxygen is only released when there is a significant drop in pO₂

• Allows aerobic respiration to be maintained

• Prevents higher rates of anaerobic respiration

• Less lactic acid is therefore produced and muscle fatigue is prevented

Why is the foetal haemoglobin curve shifted to the left?

• Higher affinity for oxygen than adult haemoglobin

• The oxygen will therefore dissociate from the mothers haemoglobin and it will transfer to the foetal haemoglobin