Haemoglobin

Question 1

What is the structure of haemoglobin?

Answer 1

• it is a globular protein that has a quaternary structure that is made of four polypeptide chains: two beta polypeptides and two alpha helices
• each subunit of these chains conatins a haem group which includes a Fe2+ ion
• each Fe 2+ ion can bind with oxygen meaning haemoglobin can carry four oxygen molecules (8)

Question 2

How many oxygen atoms can haemoglobin carry

Answer 2

• 8

Question 3

What is the function of haemoglobin?

Answer 3

• haemoglobin binds to oxygen in the lungs and transports it to respiring tissues
• each prosthetic haem group allows oxygen to reversibly bind to haemoglobin

Question 4

How does the affinity of oxygen vary with partial pressure?

Answer 4

• When there is a greater concentration of oxygen, the greater the partial pressure
• this increases the affinity of oxygen
• this is helpful as oxygen therefore binds to haemoglobin in high concentrations

Question 5

Explain positive cooperativity

Answer 5

• the initial shape of haemoglobin makes it difficult for the first oxygen molecule to bind to it as the four polypeptide subunits are closely united
• Therefore at low oxygen concentrations, very little oxygen binds to oxygen
• However, when the first oxygen molecule binds to haemoglobin, the quaternary structure of haemoglobin changes, making it easier for other oxygen molecules to bind to haemoglobin
• this means that it takes a smaller increase in partial pressure for the second oxygen molecule to bind

Question 6

What happens after the third oxygen molecule binds to haemoglobin?

Answer 6

• after the third oxygen molecule, it is harder for the last oxygen molecule to bind due to low probability, causing oxygen dissocation curves to flatten

Question 7

Draw an oxygen dissociation graph

Answer 7

notes

Question 8

If a graph is further to the left, what does that mean?

Answer 8

• haemoglobin has a higher affinity

Question 9

If the graph is further to the right, what does that mean?

Answer 9

• haemoglobin has a lower affinity

Question 10

What is affinity?

Answer 10

-The degree to which oxygen binds to haemoglobin

Question 11

What are adaptations that red blood cells have?

Answer 11

• no nucleus to increase its space to carry oxygen
• bio-concave shape to increase SA:V ratios

Question 12

Explain the effect of carbon dioxide levels on the affinity of hameoglobin

Answer 12

• the higher the concentration of co2, the lower the affinity of haemoglobin
• this means it releases oxygen more readily

Question 13

Explain the Bohr shift?

Answer 13

• At gas exchange surfaces such as the lungs , carbon dioxide is constantly removed
  -this increases the PH ofsolutions, causing haemoglobin to change shape and have a higher affinity
• At respiring tissues, carbon dioxide levels are higher, increasing acidity
• this causes haemoglobin shape to change and have a reduced affinity for oxygen
• this means it readily unloads oxygen to respiring tissues

Question 14

What does the Bohr effect ensure

Answer 14

• that respiring tissues have a high concentration of oxygen for aerobic respiration

Question 15

What are haemoglobin adaptations for high altitudes?

Answer 15

• at higher altitudes, the partial pressure of oxygen is lower
• this means haemoglobin has adapted in animals such as llamas to bind more readily to oxygen to enable them to have a high level of oxygen saturation even at low partial pressures

Question 16

How has foetal haemoglobin adapted?

Answer 16

• foetal haemoglobin has adapted to have a high affinity for oxygen, allowing it to bind to oxygen at low partial pressures to obtain oxygen from the placenta
• this means that at low partial pressures when the mothers haemoglobin is dissociating, foetal haemoglobin can bind to this oxygen at have a higher saturation

Question 17

draw oxygen dissociation curves for llamas, foetal haemoglobin

Answer 17

• notes