Module 3 - Mass transport in animals

Question 1

3 marks

The oxygen dissociation curve for heamoglobin shifts right during vigorous exercise. Explain the advanatge of this shift

Answer 1

1. Low pH due to increased CO2/ increased respiration
2. Increased dissociation of haemoglobin
3. Oygen diffuses from r.b.c to tissues

Question 2

1 mark

What is the advantage of a fall in the affinity of haemoglobin for oxygen?

Answer 2

At low ppO₂ (in the respiring tissues), a fall in haemoglobin’s affinity allows oxygen to be released to the cells for aerobic respiration.

Question 3

2 marks

How does fetal haemoglobin differ from adult haemoglobin, and why is this difference important?

Answer 3

• Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin.
• This allows the fetus to load oxygen from the mother’s blood across the placenta, even at lower ppO₂.

Question 4

2 marks

The first molecule of oxygen to bind causes a change in the shape of the haemoglobin molecule. This change of shape makes it easier for other oxygen molecules to bind to the haemoglobin molecule. Explain how the graph provides evidence for this.

Answer 4

1. At low ppO2, little increase in saturation as O2 increases
2. Then rapid rise as it gets easier for O2 to bind

Question 5

Suggest one advantage of a rise in the affinity of haemoglobin for oxygen.

Answer 5

A rise in affinity ensures rapid/more intake of oxygen in the lungs

Question 6

3 marks

How does exposure to CO affect loading and unloading of oxygen by haemologlobin

Answer 6

1. A low Po2 Hb exposed to CO has a higher affinity for oxygen than normal Hb
2. In respiring tissue its unloading less oxygen than it should
3. At high Po2 (lungs) it has a lower affinity for oxygen than normal Hb- only 50% saturation of the no CO Hb (less oxygen loaded at lungs)

Question 7

3 marks

Explain why the thickness of the aorta wall changes all the time during each cardiac cycle

Answer 7

1. Aorta wall stretches because ventricle contracts (pressure increases)
2. Aorta wall recoils because ventricle relaxes (pressure falls)
3. Maintain smooth flow / pressure

Question 8

What does atheroma lead to

Answer 8

Atheroma leads to blockage of coronary artery

Question 9

2 marks

There is a small increase in pressure and in rate of blood flow in the aorta.
Explain how this happens and its importance.

Answer 9

1. Elastic recoil of the aorta wall
2. Smooths the blood flow

Question 10

What factor limits the minimum internal diameter of the lumen of a capillary

Answer 10

Diameter of red blood cell

Question 11

2 marks

How is the pressure in the ventricle related to the thickness of ventricle wall

Answer 11

• Thickness of wall increases because ventricle wall contracts
• Contraction caused by increase in pressure

Question 12

3 marks

Explain why high blood pressure leads to the accumulation of tissue fluid

Answer 12

• High blood pressure (as ventricle contracts)= high hydrostatic pressure
• Increase in outward pressure from arteriole end of capillary
• So more tissue fluid formed

Question 13

3 marks

Why does venule end of capillary have lower blood plasma water potential

Answer 13

1. Water has left capillary
2. Proteins in blood too large to leave
3. Higher concentration of blood plasma proteins

Question 14

Why does carbonmonoxide kill people. Use loading and unloading of O2.

Answer 14

At low pO2, Hb exposed to CO has higher affinity for O2 than normal Hb
In respiring tissues it is unloading less O2 than it should
At high PO2, it has lower affinity for O2 than normal Hb- less O2 loaded to lungs

Question 15

6 marks

Explain how tissue fluid is formed and how it may be returned to the circulartory system

Answer 15

1. High hydrostatic pressure at arterial end
2. Soluble molecules pass out
3. Proteins remain - too large
4. This lower water potential at venule end
5. Water moves back into venule end via osmosis
6. Lymphatic system collects any excess tissue fluid which returns to blood

Question 16

2 marks

High absorption of salt from the diet can result in a higher than normal
concentration of salt in the blood plasma entering capillaries. This can lead to a build-up of tissue fluid. Explain how.

Answer 16

1. Higher salt results in higher blood pressure–> higher hydrostatic pressure
2. So more fluid forced out of arteriole end of capillary
   OR
3. Higher salt results in lower water potential of tissue fluid
4. So less water returns to capillary by osmosis at venule end

Question 17

6 marks

Explain how the structures of the walls of arteries, veins and capillaries are related to their functions.

Answer 17

Artery
1. thickest wall, enabling it to carry blood at high pressure / withstand pressure surges
2. most elastic tissue, which evens out pressure
3. most muscle which maintains pressure
4. muscle in wall to control blood flow
Vein
5. thin wall does not have to withstand high pressure
Capillary
6. thin wall, allowing diffusion
7. only endothelium present, allowing short diffusion pathway
All vessels
8. have endothelium that reduces friction

Question 18

Does artery or vein have larger lumen

Answer 18

Arteries have smaller lumens than veins

Question 19

3 marks

Explain how oxygen in a RBC is made available for respiration in active tissues

Answer 19

• Low pH due to increased CO2 due to increased respiration;
• Increased dissociation of haemoglobin
• Oxygen diffuses from r.b.c. to tissues

Question 20

2 marks

A decrease in the pH of blood plasma reduces the affinity of haemoglobin for oxygen.
Explain how aerobic respiration in cells leads to a change in the pH of blood plasma.

Answer 20

1. CO2 is produced
2. Forms carbonic acid
3. Hydrogen ions released

Question 21

2 marks

What is the advantage to tissue cells of a reduction in the affinity of haemoglobin for oxygen when the plasma pH decreases?

Answer 21

1. Low pH due to high rates of respiration
2. Cells need more oxygen
3. More oxygen released

Question 22

4 marks

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs.
Details of breathing are not required.

Answer 22

1. Trachea and bronchi and bronchioles
2. Down pressure gradient
3. Down diffusion gradient
4. Across alveolar epithelium
5. Across capillary endothelium

Question 23

2 marks

The oxygen dissociation curve of the fetus is to the left of that for its mother. Explain the advantage of this for the fetus.

Answer 23

1. Higher affinity for oxygen at low partial pressure
2. Oxygen moves from mother to fetus

Question 24

5 marks

Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.

Answer 24

1. Atrium has higher pressure than ventricle (due to contraction) causing atrioventricular valves to open
2. Ventricle has higher pressure than atrium (due to contraction) causing atrioventricular valves to close
3. Ventricle has higher pressure than aorta causing semilunar valve to open
4. Higher pressure in aorta than ventricle (as heart relaxes) causing semilunar valve to close
5. Contraction causes increase in pressure

Question 25

# 3 marks The oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise. Explain the advantage of this shift.

Answer 25

* Lower affinity for oxygen * To muscles/tissues * For high respiration

Question 26

The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why

Answer 26

1. Water has left the capillary 2. Proteins in blood too large to leave capillary 3. Increasing concentration of blood proteins

Question 27

# 2 marks Other than causing slow blood flow, explain one advantage of capillaries being narrow.

Answer 27

1. Short distance between blood and outside of capillary 2. Large surface area of blood in contact with walls of capillaries 3. Fast exchange / fast diffusion

Question 28

# 2 marks What is the function of the coronary arteries?

Answer 28

1. Carry oxygen 2. To heart muscles

Question 29

# 6 marks Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions.

Answer 29

**Elastic tissue** 1. Elastic tissue stretches under pressure then recoils 2. Evens out pressure / flow **Muscle** 3. Muscle contracts to reduce diameter of lumen / vasoconstriction 4. Changes blood flow **Epithelium** 5. Epithelium smooth 6. Reduces friction

Question 30

# 2 marks Give two structural features of an aorta wall and explain how they are related to the function of an aorta.

Answer 30

1. Smooth muscle withstands high blood pressure 2. Elastic tissue stretches and recoils maintains/smooths blood pressure 3. Smooth endothelium reduces friction 4. Protein coat prevents artery wall splitting

Question 31

# 6 marks Explain how oxygen is loaded, transported and unloaded in the blood.

Answer 31

1) Hb carries oxygen / has a high affinity for oxygen / oxyhaemoglobin 2) In RBC 3) Loading in lungs 4) At high partial pressure of oxygen 5) Unloads to respiring cells 6) at low partial pressure of oxygen 7) Unloading linked to higher carbon dioxide conc

Question 32

# 3 marks The oxygen dissociation curve of the foetus is to the left of that for its mother. Explain the advantage of this for the foetus.

Answer 32

1) Have a higher affinity / loads more oxygen 2) At low pO2 3) So oxygen moves from mother to fetus

Question 33

# 4 marks Explain how oxygen in a red blood cell is made available for respiration in active tissues.

Answer 33

1) Respiration increases carbon dioxide conc 2) So increases rate at which oxygen is dissociated 3) Low partial pressure of oxygen in tissues/plasma 4) So oxygen diffuses from red blood cells to tissues

Question 34

# 4 marks Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue.

Answer 34

1. permeable capillary wall 2. Thin epithelium walls, reduces diffusion distance 3. flattened endothelium cells, reduces diffusion distance 4. fenestrations, allows large molecules through 5. small diameter, gives a large surface area to volume / short diffusion distance 6. narrow lumen, reduces flow rate giving more time for diffusion 7. red blood cells in contact with wall- more time for diffusion

Question 35

# 3 marks Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. Do not include descriptions of pressure changes in the heart or the role of heart valves in your answer.

Answer 35

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

Question 36

# 1 mark Give one other way, besides ventillation, that helps to maintain the difference in oxygen concentration.

Answer 36

Circulation of blood | good blood supply due to network capillary

Question 37

Equation for pulmonary ventillation

Answer 37

PV= breathing rate x tidal volume

Question 38

# 2 marks When a person starts to breathe out, the percentage of oxygen in the air first exhaled is the same as the percentage of oxygen in the atmospheric air. Explain why.

Answer 38

1. Air is in dead space e.g. trachea, bronchi, nose (no gas exchange happens) 2. Gas exchange only in alveoli

Question 39

Equation for cardiac output

Answer 39

CO= breathing rate x stroke volume

Question 40

# 2 marks In healthy lungs, a gradient is maintained between the concentration of oxygen in the alveoli and the concentration of oxygen in the lung capillaries. Describe how ventilation helps to maintain this difference in oxygen concentration.

Answer 40

In alveolus 1. Brings in air containing a higher oxygen concentration; 2. Removes air with a lower oxygen concentration

Question 41

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

Answer 41

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

Question 42

# 2 marks Describe the advantage of the Bohr effect during intense exercise

Answer 42

1. Increases dissociation of oxygen 2. For aerobic respiration at the tissues/muscles/cells

Question 43

# 6 marks Describe the 3 stages of the cardiac cycle with reference to all the valves and the cardiac muscles in the atria and ventricles

Answer 43

1. Atrial systole 2. Atria contracts amd ventricles relax 3. Atrioventricular valve open and semi lunar valve closed 4. Ventricular systole 5. Ventricles contract and atria relax 6. AVN closed and SLV open 7. Diastole 8. Ventricles and atria are both relaxed 9. SLV closed and AVN open

Question 44

# 5 marks Explain what is meant by herd immunity and suggest the advantages of it

Answer 44

1. Herd immunity: Majority of the population is vaccinated 2. Prevents transmission of pathogen in the community 3. Reduces infection rate in population 4. Can lead to eradication of disease 5. Protects vulnerable populations, people who cannot have vaccines e.g. babies 6. Prevents future pandemics

Question 45

# 1 mark Give formula for % saturation of Hb with O2

Answer 45

(Oxygenated Hb/ maximum saturation) x 100

Question 46

# 2 marks The first molecule of oxygen to bind causes a change in the shape of the haemoglobin molecule. This change of shape makes it easier for other oxygen molecules to bind to the haemoglobin molecule. Explain how the graph provides evidence for this.

Answer 46

1. At low partial pressure of oxygen, little increase in saturation as oxygen increases 2. (then) rapid rise as it gets easier for oxygen to bind

Question 47

# 1 mark Suggest one advantage of this change in the affinity of haemoglobin for oxygen.

Answer 47

Ensures rapid / more intake of oxygen in lungs / release of oxygen in tissues

Question 48

Outline the route that blood takes through the heart

Answer 48

VC, RA, RV, Pulmonary Artery, Lungs, Pulmonary vein, LA, LV, Aorta

Question 49

How does vein structure relate to its function?

Answer 49

Thin walls, wide lumen – low pressure. Valves to prevent back flow.

Question 50

# 3 marks Most children born with Patau syndrome die in the first 12 months, often due to defects of circulation of blood. One of these defects is patent ductus arteriosus (PDA). This can result in some of the blood flowing between the aorta and the pulmonary artery. Suggest how the flow of some of the blood between the aorta and pulmonary artery could cause children to die in the first 12 months.

Answer 50

1. Some oxygenated blood from the aorta flows into pulmonary artery (mixing of deoxygenated with oxygenated blood in pulmonary artery) 2. Less oxygen delivered to cells / tissues via arteries 3. So less oxygen for aerobic respiration in cells 4. Tissue / organ doesn’t grow causing death

Question 51

# 2 marks Purpose of pulmonary artery and aorta in blood flow

Answer 51

Pulmonary artery: carries deoxygenated blood to the lungs. Aorta: carries oxygenated blood to the body.

Question 52

# 3 marks What happens to blood flow in a normal heart | Deoxygenated and oxygenated blood

Answer 52

1. Deoxygenated blood enters the right atrium, then right ventricle, and is pumped to the lungs via the pulmonary artery. 2. Oxygenated blood returns to the left atrium, then left ventricle, and is pumped to the body via the aorta. 3. Pulmonary artery: carries deoxygenated blood to the lungs. Aorta: carries oxygenated blood to the body.

Question 53

The main blood vessels and their functions

Answer 53

* Pulmonary artery - carries deoxygenated blood away from the heart, towards the lungs * Pulmonary vein - carries oxygenated blood away from the lungs, towards the heart * Coronary arteries - supply the heart with oxygenated blood * Aorta - carries oxygenated blood out of the heart and to the rest of the body * Vena cava - carries deoxygenated blood into the heart * Renal artery - supplies the kidneys with oxygenated blood * Renal vein - carries deoxygenated blood away from the kidneys, towards the heart

Question 54

# BHA version Mass transport- Hb | 5 marks

Answer 54

1. In respiring tissues, low ppo2- Hb has lower affinity for O2, more O2 unloaded 2. In lungs, high ppo2- Hb has higher affinity for O2, more O2 is loaded 3. The binding of the first O2, makes binding of further O2 easier (cooperate binding) 4. If CO2 high, curve shifts to the right and lower- Hb with lower affinity= more O2 unloaded to muscles 5. If CO2 low, curve shifts to left and higher- Hb with higher affinity= more O2 loaded in lungs

Question 55

# BHA version Hb differences of feotus, highland animal and small animals | 3 marks

Answer 55

1. Foetal Hb has higher affinity than adult- more O2 loaded 2. Highland animal Hb has higher affinity than lowland- more O2 loaded in lungs (less availability of O2 at altitude) 3. Small animal Hb has lower affinity than large organisms (large SA:V- more heat loss- high metabolism). More O2 unloaded to respiring tissues

Question 56

# 3 marks Describe structure of human Hb

Answer 56

1. A protein with quaternary structure, contains 4 polypeptides joined together 2. 4 haem groups 3. Contains 4 O2 binding sites