Haemoglobin

Question 1

Explain the adaptations of a red blood cell?

Answer 1

The biconcave shape creates a large surface area to maximize the absorption of oxygen.
No nucleus, which maximises the volume of oxygen that can be carried.
They have a thin membrane so that there is a short diffusion pathway.

Question 2

What is the structure of haemoglobin?

Answer 2

Is a protein with a quaternary structure made up of 4 polypeptide chains. Each chain contains a haem group, which contains an iron ion.

Question 3

What is oxyhaemoglobin?

Answer 3

In the lungs, oxygen associates to haemoglobin in red blood cells. At the body cells the oxygen dissociates.
Hb + 4O2 <—>HbO8

Question 4

What is affinity for oxygen?

Answer 4

The ease with which haemoglobin associates and dissociates with oxygen.
A high affinity means oxygen loads easily and unloads slowly.
A low affinity means oxygen loads slowly and unloads easily.

Question 5

Explain the shape of the dissociation curve?

Answer 5

Due to the haemoglobin shape it is difficult for the first oxygen to bind, so the binding occurs slowly.
After the first oxygen binds, the haemoglobin protein shape changes, making it easier for the next oxygen to bind, which speeds up the binding.
As the haemoglobin approaches saturation it takes longer for the forth oxygen to bind due to the shortage of remaining binding sites.