3.4.1 Mass Transport In Animals

Question 1

Describe the role of red blood cells & haemoglobin in oxygen transport

Answer 1

• red blood cells contain lots of haemoglobin
  
  • no nucleus & biconcave -> more space for Hb, high SA:V ratio & short diffusion distance
• Hb associates with / binds / loads oxygen at gas exchange surfaces (lungs) where partial pressure of oxygen (pO2) is high
• this forms oxyhaemoglobin which transports oxygen
  
  • each can carry four oxygen molecules, one at each haem group
• Hb disassociates form / unloads oxygen near cells / tissues where pO2 is low

Question 2

Describe the structure of haemoglobin

Answer 2

• protein with a quaternary structure
• made of 4 polypeptide chains
• each chain contains a haem group containing an iron ion (Fe2+)

Question 3

Describe the loading, transport and unloading of oxygen in relation to the oxyhaemoglobin dissociation curve

Answer 3

Areas with low pO2 - respiring tissues
- Hb has a low affinity for oxygen
- so oxygen readily unloads / dissociates with Hb
- so % saturation is low

Ares with high pO2 - gas exchange surfaces
- Hb has a high affinity for oxygen
- so oxygen readily loads / associates for oxygen
- so % saturation is high

Question 4

Explain how the cooperative nature of oxygen bindings results in an s-shaped (sigmoid) oxyhaemoglobin curve

Answer 4

1. Binding of first oxygen changes tertiary / quaternary structure of haemoglobin
2. This incovers haem group binding sites, making further binding of oxygens easier

Question 5

Describe evidence for the cooperative nature of oxygen binding

Answer 5

• a low pO2 as oxygen increases there is little / slow increase in % saturation of Hb with oxygen
  
  • when first oxygen is binding
• at high pO2, as oxygen increases there is a big / rapid increase in % saturation of Hb with oxygen
  
  • showing it has got easier for oxygens to bind

Question 6

What is the Bohr effect?

Answer 6

Effect of C02 concentration on dissociation of oxyhaemoglobin -> curve shifts to the right

Question 7

Explain effect of C02 concentration on the dissociation of oxyhaemoglobin

Answer 7

1. Increasing blood C02 e.g. due to increased rate of respiration
2. Lowers blood pH (more acidic)
3. Reducing Hb’s affinity for oxygen as shape / tertiary/ quaternary structure changes slightly
4. So more / faster unloading of oxygen to respiring cells at a given pO2

Question 8

Explain the advantage of the Bohr effect (e.g. during exercise)

Answer 8

• more dissociation of oxygen -> faster aerobic respiration / less anaerobic respiration -> more ATP prodcued

Question 9

Explain why different types of haemoglobin can have different oxygen transport properties

Answer 9

• different types of Hb are made of polypeptide chains with slightly different amino acid sequences
• resulting in different tertiary/quaternary structures / shapes
• so they have different affinities for oxygen

Question 10

Explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport properties

Answer 10

Curve shift left - haemoglobin has higher affinity for O2:
- More O2 associates with Hb more readily
- at gas exchange surface where pO2 is lower
- e.g. organisms in low O2 environments - high altitudes, underground, or foetuses

Curve shift right - Hb has lower affinity for O2:
- more O2 dissociates from Hb more readily
- at respiring tissues were O2 is needed
- e.g organisms with high rates of respiration / metabolic rate (may be small or active)

Question 12

Describe the general pattern of blood circulation in a mammal

Answer 12

1. Deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
2. Oxygenated blood in left side pumped to rest of the body; deoxygenated returns to right side

Question 13

Suggest the importance of a double circulatory system

Answer 13

• prevents mixing of oxygenated/deoxygenated blood
  
  • so blood pumped to body is fully saturated with oxygen for aerobic respiration
• blood can be pumped to body at a high pressure (after being lower from lungs)
  
  • substances taken to / removed from body cells quicker / more efficiently

Question 14

Draw a diagram to show the general pattern of blood circulation in a mammal

Answer 14

Question 15

Name the blood vessels entering and leaving the heart and lungs

Answer 15

• vena cava = transports deoxygenated blood from respiring body tissues -> heart
• pulmonary artery = transports deoxygenated blood from heart -> lungs
• pulmonary vein = transports oxygenated blood from lungs -> heart
• aorta = transports oxygenated blood from heart -> respiring body tissues

Question 16

Name the blood vessels entering and leaving the kidneys

Answer 16

• renal arteries = oxygenated blood -> kidneys
• renal veins = deoxygenated blood to vena cava from kidneys

Question 17

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

Answer 17

• coronary arteries = located on surface of the heart, branching from aorta

Question 18

Diagram to show the gross structure of the human heart

Answer 18

Question 19

Suggest why the wall of the left ventricle is thicker than the right

Answer 19

• thicker muscle to contract with greater force
• to generate higher pressure to pump blood around entire body

Question 20

Explain atrial systole

Answer 20

-atria contract
- so their volume decreases, pressure increases
- atrioventricular valve opens when pressure in atria exceeds pressure in ventricles
- semilunar valve remains shit as pressure in arteries exceeds pressure in ventricles
- so blood pushed into ventricles

Question 21

Explain ventricular systole

Answer 21

• ventricles contract
• so their volume decreases, pressure increases
• atrioventricular valves shut when pressure in ventricles exceeds pressure in atria
• semilunar valves open when pressure in ventricles exceeds pressure in arteries
• so blood is pushed out of heart through arteries

Question 22

Explain diastole

Answer 22

• atria & ventricles relax
• so their volume increases, pressure decreases
• semilunar valves shut when pressure in arteries exceeds pressure in ventricles
• atrioventricular valves open when pressure in atria exceeds pressure in ventricles
• so blood fills atria via veins & flows passively to ventricles

Question 23

Explain the graph

Answer 23

Semilunar valves closed:
- pressure increases [] artery higher than in ventricle
- to prevent back flow of blood from artery to ventricles
Semilunar valves open:
- when pressure in ventricle is higher than in [] artery
- so blood flows from ventricle to artery
Atrioventricular valves closed:
- pressure increases ventricle high than atrium
- to prevent back flow of blood from ventricles to atrium
Atrioventricular valves open:
- when pressure in atrium is higher than in ventricle
- so blood flows from atrium to ventricle

Question 24

How can heart rate be calculated from cardiac cycle data?

Answer 24

Heart rate (beats per minute) = 60 seconds / length of one cardiac cycle (seconds)

Question 25

Cardiac output equation

Answer 25

Cardiac output (volume of blood pumped out of heart per minute) = stroke volume (volume of blood pumped in each heart beat) x heart rate (bpm)

Question 26

Explain how the structure of arteries related to their functions

Answer 26

Function = carry blood away from the heart at high pressure 1. Thick smooth muscle tissue = can contract and control / maintain / withstand blood flow / pressure 2. Thick elastic tissue = can stretch as ventricles contract and recoil as ventricles relax, to reduce pressure surges / even out blood pressure / maintain high pressure 3. Thick wall = withstands high pressure / prevents bursting 4. Smooth / folded endothelium = reduces friction / can stretch 5. Narrow lumen = increases / maintains high pressure

Question 27

Explain how the structure of arterioles relates to their function

Answer 27

Function = (division of arteries to smaller vessels which can) direct blood to different capillaries / tissues 1. Thicker smooth muscle layer than arteries - contracts -> narrows lumen (vasoconstriction) -> reduces blood flow to capillaries - relaxes -> widens lumen (vasodilation) -> increases blood flow to capillaries 2. Thin elastic layer -> pressure surges are lower ( as further from heart / ventricles)

Question 28

Explain how the structure of capillaries are related to their function

Answer 28

Function = allow efficient exchange of substances between blood snd tissue fluid 1. Wall is a once cell layer of endothelial cells -> reduces diffusion distance 2. Capillary bed - large network of branched capillaries -> increases surface area for diffusion 3. Small diameter / narrow lumen -> reduces blood flow rate al more time for diffusion 4. Pores in walls between cells -> allow larger substances through

Question 29

Explain how the structure of veins relates to their function

Answer 29

Function = carry blood back to heart at low pressure 1. Wider lumen than arteries -> less resistance to blood flow 2. Very little elastic and muscle tissue -> blood pressure lower 3. Valves -> prevent back flow of blood

Question 30

Explain the formation of tissue fluid

Answer 30

At the arteriole end of capillaries: 1. High hydrostatic pressure inside capillaries (due to contraction of ventricles) than tissue fluid (so net outward force) 2. Forcing water and dissolved substances out of capillaries 3. Large plasma proteins remain in capillary

Question 31

Explain the return of tissue fluid to the circulatory system

Answer 31

At the venule end of capillaries 1. Hydrostatic pressure reduces as fluid leaves capillary also due to friction 2. Due to water loss, an increasing concentration of plasma proteins lowers water potential in capillary below that of tissue fluid 3. Water enters capillaries from tissue fluid by osmosis down a water potential gradient 4. Excess water taken up by lymph capillaries and returned to circulatory system through veins

Question 32

What is a risk factor snd examples for cardiovascular disease

Answer 32

- an aspect of a persons lifestyle or substances in a persons body / environment that have been shown to be linked to an increased rate of disease - e.g. age, diet high in salt or unsaturated fat, smoking, lack of exercise, genes