Topic 3D: Mass Transport in Animals

Question 1

Explain a property of iron ions that enables these ions to carry out their role in red blood cells. [2]

Answer 1

1. Charged;
2. Bind to oxygen

Question 2

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind. Explain why. [2]

Answer 2

1. Binding of first oxygen changes tertiary structure of haemoglobin;
2. Uncovers another binding site

Question 3

Why is it important for animals that need a lot of energy to have haemoglobin with a lower affinity to oxygen? [3]

Answer 3

1. Haemoglobin unloads more readily;
2. More oxygen to cells;
3. More respiration

Question 4

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhemoglobin. [2]

Answer 4

1. Increases oxygen dissociation;
2. (By) decreasing (blood) pH

Question 5

Explain how changes in the shape of haemoglobin result in the S-shaped oxyhemoglobin dissociation curve. [2]

Answer 5

1. First oxygen binds causing change in shape;
2. Allows more O2 to bind

Question 6

What is the advantage to tissue cells of a reduction in the affinity of haemoglobin for oxygen when the blood pH decreases? [2]

Answer 6

1. Low pH because high rate of respiration;
2. Cells need more O2;
3. More O2 released

Question 7

Explain the meaning of quaternary structure. [1]

Answer 7

1. (Molecule contains) more than one polypeptide (chain)

Question 8

What is the formula for calculating the percentage saturation of haemoglobin with oxygen? [1]

Answer 8

Percentage saturation of haemoglobin with oxygen = oxygenated haemoglobin ÷ maximum saturation x 100

Question 9

There is less oxygen at high altitudes than at sea level. People living at high altitudes have move red blood cells than people living at sea level. Explain the advantage of this to people living at high altitude. [2]

Answer 9

1. More haemoglobin;
2. So can load more oxygen (in the lungs)

Question 10

Shrews have haemoglobin with a lower affinity to oxygen than elephant’s haemoglobin has. Explain this advantage. [3]

Answer 10

1. (At the tissues at low pO2) the shrew’s haemoglobin is less saturated with oxygen;
2. Oxyhaemoglobin dissociates more readily;
3. Allowing greater respiration rate

Question 11

Explain how oxygen is loaded, transported and unloaded in the blood. [6]

Answer 11

1. Haemoglobin carries oxygen;
2. Loading in lungs;
3. at high pO2;
4. Unloads to respiring cells;
5. at low pO2;
6. Unloading linked to higher carbon dioxide (concentration)

Question 12

What are the adaptations of red blood cells to their function? [3]

Answer 12

1. Large surface area to volume ration so fast diffusion of oxygen into and out of the cell;
2. Flat so short diffusion pathways;
3. No nucleus so more space for haemoglobin