Transport Of Oxygen By Haemoglobin

Question 1

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

Answer 1

It does not bind to the oxygen evenly.

Question 2

What is the graph of the relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen known as?

Answer 2

Oxygen dissociation curve.

Question 3

Why is the dissociation curve for adult haemoglobin shallow initially?

Answer 3

The shape of the haemoglobin molecule makes it difficult for the first oxygen molecule to bind to one of the sites on its four polypeptide subunits because they are closely united.

Question 4

What does the binding of the first oxygen molecule change?

Answer 4

This changes the Quaternary structure of the haemoglobin molecule, causing it to change shape make it easier for the subunits to bind to another oxygen molecule.

Question 5

What does the binding of the first oxygen molecule induce?

Answer 5

This induces the other subunits to bind to an oxygen molecule.

Question 6

What is positive cooperativity?

Answer 6

This is where the binding of the first molecule makes binding of the second easier and so on, this therefore result in the curve steepening.

Question 7

What causes the curve to steepen?

Answer 7

Positive cooperativity.

Question 8

Why is it more difficult for the third oxygen molecule to bind?

Answer 8

This is because the majority of the binding sites are occupied so it is less likely that a single oxygen molecule will find an empty site to buy into this therefore results in the gradient of the curve reducing and the graph flattening off.

Question 9

What does an oxygen dissociation curve that is further to the left show?

Answer 9

This shows a great affinity for haemoglobin for oxygen.

Question 10

What does an oxygen dissociation curve to the right show?

Answer 10

This shows that the affinity is lower.

Question 11

What happens to the affinity of haemoglobin in the presence of carbon dioxide?

Answer 11

The affinity is reduced.

Question 12

What is the Bohr effect?

Answer 12

This is where the greater the concentration of carbon dioxide, the more readily the haemoglobin releases its oxygen.

Question 13

Why is the concentration of carbon dioxide is low on gas exchange services?

Answer 13

This is because it defuses across the exchange surface and is excreted from the organism.

Question 14

What way does the oxygen dissociation curve shift when carbon dioxide concentrations are low?

Answer 14

To the left.

Question 15

Why is the concentration of carbon dioxide high at respiring tissues?

Answer 15

This is because carbon dioxide is a byproduct of respiration.

Question 16

How does the increased carbon dioxide concentration affect the affinity?

Answer 16

It lowers it which means that oxygen is readily unloaded from the haemoglobin into the muscle cells.

Question 17

Which way the high concentrations of carbon dioxide is shift the oxygen dissociation curve?

Answer 17

To the right.

Question 18

What is the key relationship between the amount of carbon outside and how readily haemoglobin releases its oxygen?

Answer 18

The greater the concentration of carbon dioxide, the more readily haemoglobin releases its oxygen.

Question 19

Why does haemoglobin have a reduced affinity for oxygen in the presence of carbon dioxide is?

Answer 19

This is because dissolved carbon dioxide is acidic and the low pH causes haemoglobin to change shape.

Question 20

What is constantly being removed at the gas exchange surface?

Answer 20

Carbon dioxide

Question 21

Why is the pH slightly raised at the gas exchange surface?

Answer 21

This is because of the low concentration of carbon dioxide.

Question 22

How does a high pH change the shape of haemoglobin and it’s affinity?

Answer 22

It changes it to one which has a high affinity and can therefore load oxygen readily.

Question 23

What does the increased affinity due to the low carbon dioxide concentration also cause?

Answer 23

It increases the affinity of haemoglobin for oxygen so it is harder for the oxygen to dissociate but this is good because it means it is not released while being transported in the blood to the tissues.

Question 24

What is produced by respiring cells and how does this affect the affinity for oxygen?

Answer 24

Carbon dioxide is produced which causes a lower affinity for oxygen so oxygen is easily given to the respiring tissues.

Question 25

What ensures that there is a flexible way of providing sufficient oxygen for respiring tissues?

Answer 25

The affinity for oxygen the changes depending on how much respiration takes place and whereabouts in the body the haemoglobin is, this means that oxygen is loaded and unloaded where it is necessary and to the amounts needed.

Question 26

What are the knock on effects of high rate of respiration?

Answer 26

The higher the rate of respiration the more carbon dioxide that is produced and therefore the lower the pH. This means that there is a greater haemoglobin shape change and therefore the more readily oxygen is unloaded meaning that more oxygen is available for respiration.

Question 27

Why do different species have different oxygen dissociation curves?

Answer 27

This is because they are adapted to live in different environments and conditions.