3. Haemoglobin

Question 1

Haemoglobin

Answer 1

Haemoglobins are a group of similar molecules found in a wide variety of living things.
Haemoglobin is a large protein with a quaternary structure – it is made up of 4 polypeptide chains.
Each chain has a haem group which contains iron which gives haemoglobin its red colour
The function of Haemoglobin…is to transport oxygen.Each haemoglobin molecule can carry 4 oxygen molecules

Question 2

the partial pressure of oxygen (pO2)

Answer 2

a measure of oxygen concentration. The greater the concentration of dissolved oxygen in cells, the higher the partial pressure.

Question 3

Why is the graph is S shaped?

Answer 3

This is because when haemoglobin combines with the first oxygen molecule, its shape alters in a way that makes it easier for other molecules to join.
But as the haemoglobin becomes more saturated it gets harder for more oxygen molecules to join.
As a result, the curve has a steep bit in the middle where its easy for oxygen molecules to join and shallow bits at either end where its harder

Question 4

Position of curve - left vs right

Answer 4

1. The further to the LEFT the curve is the greater the affinity of the haemoglobin for oxygen. This means it will take up oxygen readily, but will release it less easily.
2. The further to the RIGHT the curve is the lower the affinity of the haemoglobin for oxygen so the oxyhaemoglobin will unload its oxygen readily.

Question 5

The effect of CO2

Answer 5

In respiring tissues, eg. muscle carbon dioxide is produced. This is acidic in solution and lowers the pH. This changes the shape of the haemoglobin molecule and the curve is shifted to the right. The haemoglobin has a lower affinity for oxygen and unloads it.
‘the Bohr effect’ or ‘Bohr shift’

Question 6

In the lungs…
vs
In the tissues…

Answer 6

In the lungs…
Carbon dioxide is being removed therefore the pH is higher and haemoglobin has a high affinity for oxygen and loads up with it.
In the tissues…
Carbon dioxide is produced shifting the curve to the right and favouring the dissociation of osyhaemoglobin

Question 7

Foetal Haemoglobin

Answer 7

The oxygen dissociation curve is to the left of adult haemoglobin showing that it has a higher affinity for oxygen.
Fetal hemoglobin has a higher affinity for Ŏ, at all partial pressures.
• This ensures that O, is transferred to the fetus from the maternal blood across the placenta. • The PO, in fetal tissues is very low due to the high metabolic rate associated with fetal growth rates.

Although fetal Hb has a higher affinity for oxygen in such a low partial pressure environment of the fetal tissue it unloads oxygen readily.

Question 8

Myoglobin

Answer 8

Protein found in the muscle cells of animals. It functions as an oxygen storage unit providing oxygen to the working muscles. Diving mammals such as seals and whales are able to remain submerged for long periods because they have greater amounts of myoglobin in their muscles than other animals do

Question 9

golden rule

Answer 9

To the Left, for Low oxygen environments

To the Right for high Rates of Respiration

Question 10

Think

Answer 10

Think…
Activity level
Surface area to volume ratio
Low oxygen environment