3.4.1 Mass transport in animals

Question 1

What is the role of haemoglobin in red blood cells?

Answer 1

Haemoglobin binds to oxygen in the lungs to form oxyhaemoglobin and releases oxygen in the tissues.

Question 2

What is meant by the quaternary structure of haemoglobin?

Answer 2

The quaternary structure refers to haemoglobin being made of four polypeptide chains, each associated with a haem group containing an iron ion (Fe2+).

Question 3

Explain the cooperative nature of oxygen binding in haemoglobin.

Answer 3

When the first oxygen molecule binds to haemoglobin, it causes a conformational change, making it easier for the second and third oxygen molecules to bind.

Question 4

What does the oxyhaemoglobin dissociation curve show?

Answer 4

It shows the relationship between the partial pressure of oxygen (pO2) and the percentage saturation of haemoglobin with oxygen.

Question 5

How does carbon dioxide concentration affect haemoglobin’s affinity for oxygen (Bohr effect)?

Answer 5

Increased carbon dioxide concentration lowers blood pH, causing haemoglobin to reduce its affinity for oxygen and release more oxygen to tissues.

Question 6

Why do different animals have different types of haemoglobin?

Answer 6

Different types of haemoglobin are adapted to the oxygen availability in their environment, with variations in oxygen affinity to suit high altitude, low oxygen, or active lifestyles.

Question 7

Name the blood vessels entering and leaving the heart.

Answer 7

The vena cava and pulmonary veins enter the heart; the pulmonary artery and aorta leave the heart.

Question 8

Name the blood vessels associated with the lungs and kidneys.

Answer 8

Pulmonary artery and pulmonary vein (lungs); renal artery and renal vein (kidneys).

Question 9

What is the function of coronary arteries?

Answer 9

Coronary arteries supply oxygenated blood to the heart muscle.

Question 10

Describe the pressure and volume changes in the left ventricle during the cardiac cycle.

Answer 10

During systole, ventricular pressure increases as the ventricle contracts, causing the aortic valve to open and blood to be ejected. During diastole, pressure decreases as the ventricle relaxes and fills with blood.

Question 11

How does the structure of arteries relate to their function?

Answer 11

Arteries have thick walls with elastic tissue to withstand high pressure and smooth muscle to maintain blood flow.

Question 12

How does the structure of veins relate to their function?

Answer 12

Veins have thin walls and wide lumens to accommodate low-pressure blood flow, with valves to prevent backflow.

Question 13

How does the structure of arterioles relate to their function?

Answer 13

Arterioles have a thick layer of smooth muscle to regulate blood flow by constriction or dilation.

Question 14

How does the structure of capillaries enable exchange?

Answer 14

Capillaries have walls one cell thick to provide a short diffusion pathway, and their extensive network increases surface area for exchange.

Question 15

How is tissue fluid formed?

Answer 15

Tissue fluid is formed when hydrostatic pressure at the arterial end of capillaries forces water and small molecules out of the blood plasma.

Question 16

How is tissue fluid returned to the circulatory system?

Answer 16

At the venous end of capillaries, reduced hydrostatic pressure and the osmotic gradient caused by plasma proteins cause water to re-enter the blood by osmosis. Excess fluid is drained by the lymphatic system.

Question 17

Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. (3)

Answer 17

1. Renal vein;
2. Vena cava to right atrium;
3. Right ventricle to pulmonary artery;

Question 18

Explain how water from tissue fluid is returned to the circulatory system. (4)

Answer 18

1. (Plasma) proteins remain
2. (Creates) water potential gradient
   OR
   Reduces water potential (of blood);
3. Water moves (to blood) by osmosis;
4. Returns (to blood) by lymphatic system;

Question 19

Explain how an arteriole can reduce the blood flow into capillaries. (2)

Answer 19

1. Muscle contracts;
2. Constricts/narrows arteriole/lumen;

Question 20

Describe the advantage of the Bohr effect during intense exercise. (2)

Answer 20

1. Increases dissociation of oxygen;

Accept unloading/ release/reduced affinity for
dissociation

2. For aerobic respiration at the tissues/muscles/cells
   OR
   Anaerobic respiration delayed at the tissues/muscles/cells
   OR
   Less lactate at the tissues/muscles/cells;

Question 21

Describe and explain the effect of increasing carbon dioxide concentration
on the dissociation of oxyhaemoglobin. (2)

Answer 21

1. Increases/more oxygen dissociation/unloading

OR
Deceases haemoglobin’s affinity for O2;
Accept more readily
Accept releases more O2

2. (By) decreasing (blood) pH/increasing acidity;
   Reject if reference made to active site

Question 22

Name the blood vessels that carry blood to the heart muscle.

Answer 22

Coronary arteries;

Question 23

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

Answer 23

1. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin;
2. Creates / leads to / uncovers second / another binding site

Question 24

Explain the role of the heart in the formation of tissue fluid. (2)

Answer 24

1. Contraction of ventricle(s) produces high blood / hydrostatic pressure;
2. (This) forces water (and some dissolved
   substances) out (of blood capillaries);
3. Do not accept contraction / pumping of the
   heart
4. Reject blood / plasma / tissue fluid forced out