Haemoglobin Transport

Question 1

What is partial pressure of oxygen?

Answer 1

• Measure of oxygen concentration

* The higher the concentration of dissolved oxygen in cells, the higher the partial pressure

Question 2

What is the partial pressure of carbon dioxide?

Answer 2

Measure of the concentration of CO2 in a cell

Question 3

What happens when haemoglobin is exposed to different partial pressures of oxygen?

Answer 3

Does not bind evenly

Question 4

What is the oxygen dissociation curve?

Answer 4

Graph of relationship between saturation of haemoglobin with oxygen and partial pressure of oxygen

Question 5

Why is initial binding of oxygen difficult for haemoglobin? ( Explanation of oxygen dissociation curve )

Answer 5

• Shape of the haemoglobin molecule makes it difficult for the first oxygen molecule to bind to one of the sites on its four polypeptide units
• This is because they closely united
• At low oxygen concentrations, little oxygen binds to haemoglobin

Question 6

Why is binding made easier past the first oxygen molecule?

Answer 6

• Binding of first oxygen molecule changes the Quaternary structure of the molecule, causing it to change shape
• This change in shape makes it easier for the other subunits to bind to an oxygen molecule
• Binding of first oxygen molecule induces other subunits to bind to an oxygen molecule

Question 7

What is positive co-operability? ( Explanation of oxygen dissociation curve )

Answer 7

• It takes a smaller increase in the partial pressure of oxygen to bind the second oxygen molecule than it did to bind the first one.
• Binding of the first molecule makes the binding of the second one easier and so on, gradient of the curve steepens

Question 8

What occurs after the binding of the third oxygen molecule?

Answer 8

• It may be easier for the haemoglobin to bind the fourth molecule, it is actually harder in practice
• This is because of probability, with the majority of binding sites occupied it is less likely that a single oxygen molecule will find an empty site to bind to.
• Gradient of the curve of the reduces and the graph flattens off

Question 9

What does it mean if the oxygen dissociation curve is to the left?

Answer 9

• Further tot he left the curve, the greater the affinity of haemoglobin for oxygen
• Loads oxygen readily, but unloads less easily

Question 10

What does it mean if the oxygen dissociation curve is to the right?

Answer 10

• Lower the affinity of haemoglobin for oxygen

* Loads oxygen less readily, but unloads it more easily