Haemoglobin

Question 1

Low partial pressure

Answer 1

At a low partial pressure, haemoglobin has low affinity for oxygen and so unloads oxygen more readily to respiring tissue.

Question 2

High partial pressure

Answer 2

At a high partial pressure of oxygen haemoglobin has a high affinity for oxygen and so loads with oxygen more readily.

Question 3

Haemoglobin structure

Answer 3

• haemoglobin is a quaternary protein made up of 4 polypeptide chains
• at the centre of each chain is a prosthetic group -> an iron ion
• haemoglobin can exist without any O2 bound to t - deoxyhaemoglobin, and fully loaded with O2-oxyhaemoglobin
• it can also exist with 1,2 or 3 oxygen molecules

Question 4

The 02 dissociation curve in the S shape because…

Answer 4

• the first O2 molecule finds it difficult to bind to the haemoglobin, when it does it changes the shape of the haemoglobin molecule making it much easier for the next 2 to bind - cooperative binding
• the last one, again, find it difficult to bind due to there ring only 1 remaining binding site

Question 5

During exercise there is a shift of the oxygen dissociation curve…

Answer 5

During exercise there is a shift to the right of the oxygen dissaciation curve. This is because of the increased CO2 during exercise lowers the pH of the blood - changing the shape of the haemoglobin molecule. This lowers its affinity for oxygen so it unloads more readily to respiring tissues.

Question 6

Low oxygen environment

Answer 6

Animals which live in low oxygen environment (low ppO2) haemoglobin have a high affinity for oxygen so load with oxygen more readily.