Mass Transport in Mammals: Oxygen Transport

Question 1

What is the structure of haemoglobin?

Answer 1

1. It is a protein that consists of four polypeptide chains and four haem groups.
2. The haem groups contain iron ions.
3. Each haem group can bind to up to 4 oxygen molecules to form oxyhemoglobin.

Question 2

What is the role of haemoglobin?

Answer 2

The haem groups bind to oxygen and allow it to be carried around the body to respiring cells for respiration and the release of energy.

Question 3

What us meant by oxygen affinity?

Answer 3

The ability of haemoglobin to bind to or attract oxygen.

Question 4

What is meant by the saturation of haemoglobin?

Answer 4

The number of oxygen molecules that have bound to the haemoglobin molecules.

Question 5

How does the partial pressure of oxygen affect the oxygen? affinity of haemoglobin

Answer 5

The higher the partial pressure the higher the oxygen affinity.

Question 6

Where does oxygen association and dissociation happen?

Answer 6

1. In the alveoli, the partial pressure of oxygen is high. The oxygen affinity of the haemoglobin is high, so oxygen loading happens.
2. Near respiring cells, where the oxygen partial pressure in the blood is low because the cells are taking it in for respiration, the oxygen affinity of haemoglobin is low, so oxygen unloading happens.

Question 7

Draw an oxygen dissociation curve. Explain why it is an S-shape.

Answer 7

1. As the oxygen partial pressure increases, the affinity of haemoglobin for oxygen also increases, meaning the first oxygen molecule binds to the haemoglobin molecules and the saturation increases. This is why at the start of the graph the line goes up.
2. After the first oxygen molecule has bound to the haemoglobin, it changes shape, and that makes it easier for other oxygen molecules to bind. This means the saturation increases rapidly and the line gets steeper.
3. The line then curves because it is very unlikely that the fourth oxygen molecule will bind to the haemoglobin so the increase in saturation does not happen at such a quick rate.

Question 8

What us the Bohr effect and what does it change about the oxygen Dissociation curve?

Answer 8

1. Carbon dioxide is an acidic gas. This means that an increase in carbon dioxide concentration makes the blood more acidic and causes the ionic bonds that hold the tertiary structure of the haemoglobin together to break and the protein to change shape. This causes the haemoglobin’s oxygen affinity to decrease and for it to unload the oxygen. This means that at lower partial pressures of oxygen, the saturation of oxygen will be lower.
2. This shifts the curve to the right.

Question 9

Where does the Bohr effect occur and why is it advantageous?

Answer 9

1. Near respiring cells where the carbon dioxide concentration is higher because the cells are respiring and releasing carbon dioxide the haemoglobin will have a lower affinity for oxygen at lower oxygen partial pressures.
2. The oxygen unloads and the cells can use it for respiration.

Question 10

How and why is the oxygen Dissociation curve different for organisms that live in low-oxygen environments?

Answer 10

1. The curve is more to the left compared to human haemoglobin.
2. This is because animals that live in places where there is a low amount of oxygen have haemoglobin that has a higher affinity for oxygen.
3. This means that the haemoglobin becomes saturated at lower partial pressures.

Question 11

How and why is the oxygen Dissociation curve different for organisms that live in high-oxygen environments?

Answer 11

1. The curve is more to the right compared to human haemoglobin.
2. This is because animals that live in places where there is a high amount of oxygen have haemoglobin that has a lower affinity for oxygen.
3. This means that at certain partial pressures of oxygen, their haemoglobin binds to oxygen-less easily compared to human haemoglobin and only becomes saturated at higher partial pressures.