Section 3 - Unit 7: Mass Transport Flashcards
(84 cards)
1
Q
Explain how oxygen is loaded, transported and unloaded in the blood (6 marks)
A
- Haemoglobin carries oxygen
- Uptake in lungs;
- At high p.O2;
- Releases to respiring cells
- At low p.O2;
- Unloading linked to higher carbon dioxide concentration
2
Q
Describe the path by which oxygen goes from an alveolus to the blood (2 marks)
A
- Through alveolar epithelium
- Through capillary epithelium
3
Q
Describe how ventilation helps to maintain a difference in oxygen concentration in the lungs (2 marks)
A
- Brings in air containing a higher oxygen concentration
- Removes air with a lower oxygen concentration
4
Q
Suggest why blood returning to the heart from the lungs contains some carbon dioxide (2 marks)
A
- Concentrations reach equilibrium
- Diffusion occurs when there is a concentration gradient
5
Q
State two ways in which blood plasma is different from tissue fluid (2 marks)
A
- Larger proteins
- More glucose
6
Q
Explain how the left ventricle causes the blood to be at high pressure (1 mark)
A
- It contracts
7
Q
Explain why blood pressure decreases along the length of the capillary (2 marks)
A
- Loss of fluid/volume
- Friction/resistance of capillary wall
8
Q
Explain how the shape of a red blood cell allows it to take up a large amount of oxygen in a short time (2 marks)
A
- Large surface area to volume ratio
- For diffusion
9
Q
Explain why producing a much higher ventricular blood pressure than normal can cause tissue fluid to build up outside the blood capillaries (2 marks)
A
- More fluid forced out of blood/capillary
- Less fluid returns back to the capillary (due to high blood pressure)
10
Q
Suggest how widening of blood vessels can reduce ventricular blood pressure (2 marks)
A
- Larger lumen
- This reduces blood pressure (less friction)
11
Q
State which blood vessel carries oxygenated blood away from the heart (1 mark)
A
- Aorta
12
Q
State which blood vessel carries deoxygenated blood to the heart (1 mark)
A
- Vena Cava
13
Q
Explain how the highest blood pressure is produced in the left ventricle (1 mark)
A
- Strongest/stronger contractions
14
Q
Suggest why having a hole between the right and the left ventricles means that sufficient oxygen doesn’t reach the rest of the body tissues (2 marks)
A
- Oxygenated and deoxygenated blood mix
- So a lower volume of oxygenated blood leaves left ventricle
15
Q
Describe the role of haemoglobin in supplying oxygen to the tissues of the body (2 marks)
A
- Oxyhaemoglobin formed/haemoglobin is loaded/associates with oxygen in area of higher ppO2
- Oxygen is unloaded in an area of lower ppO2 (in tissues)
16
Q
Explain how tissue fluid is formed (2 marks)
A
- Outward pressure of 3.2 kPa
- Forces small molecules out of capillary
17
Q
Explain how high blood pressure leads to an accumulation of tissue fluid (3 marks)
A
- High blood pressure = high hydrostatic pressure
- This increases outward pressure from (arterial) end of capillary
- So more tissue fluid formed/less tissue fluid is reabsorbed
18
Q
Explain why 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 (3 marks)
A
- Water has left the capillary
- Proteins in blood are too large to leave capillary
- Increasing concentration of blood proteins (and thus water potential)
19
Q
Explain the function of the coronary arteries (2 marks)
A
- Carries oxygen/glucose
- To heart muscle/tissues/cells
20
Q
Explain why although the speed of blood flow in an arteriole is greater than the speed of blood flow in a capillary, blood does not accumulate in the arterioles (1 mark)
A
- Area of capillaries is much larger than arterioles
21
Q
Other than causing slow blood flow, explain one advantage of capillaries being narrow (1 mark)
A
- Fast diffusion
22
Q
What factor limits the minimum internal diameter of the lumen of a capillary (1 mark)
A
- Diameter of blood cell
23
Q
Explain why the volume of blood leaving the capillary network into the veins is less than the volume of blood entering from the arteries (1 mark)
A
- Fluid in tissue fluid
24
Q
Explain the importance of maintaining a constant blood pH (3 marks)
A
- Haemoglobin protein in blood is sensitive to pH
- Resultant change of tertiary structure
- So less oxygen binds to haemoglobin
25
Explain the advantage of the oxygen dissociation curve for haemoglobin shifting to the right during vigorous exercise (3 marks)
- Lower affinity for oxygen
- Faster unloading to muscles/tissues/cells
- For rapid respiration
26
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta (5 marks)
- Atrium has higher pressure than ventricle causing atrioventricular valves to open
- Ventricle has higher pressure than atrium causing atrioventricular valves to close
- Ventricle has higher pressure than aorta causing semilunar valve to open
- Higher pressure in aorta than ventricle causing semilunar valve to close
- Contraction causes increase in pressure
27
The oxygen dissociation curve of the fetus is to the left of that for its mother - explain the advantage of this for the fetus (2 marks)
- Higher affinity/partial pressure
| - So oxygen moves from mother to fetus
28
Name the blood vessel to which an artificial heart is connected (1 mark)
- Aorta
29
Suggest why the artificial heart mainly helps the left ventricle and not the right ventricle (2 marks)
- Left ventricle pumps to whole body
| - So it does most work/produces a greater pressure
30
Suggest why the pulse felt can be used to measure heart rate (2 marks)
- The pulse is caused by pressure
| - From one contraction
31
Explain why an arteriole is described as an organ (1 mark)
- Made up of more than one tissue
32
Explain how muscle fibres in an arteriole reduce blood flow to capillaries (2 marks)
- The muscle contracts
| - And narrows the capillaries
33
Give the advantage of blood flow in capillaries being slow (1 mark)
- More time for exchange of substances
34
Explain why a lack of protein in the blood causes a build up of tissue fluid (3 marks)
- Water potential in capillary not as low
- So no water removed into capillary
- By osmosis, causing the build up of tissue fluid
35
Explain why the values for the pressure in the xylem are negative (1 mark)
- Inside xylem lower than atmospheric pressure
36
Explain the difference in thickness between the pulmonary artery and the pulmonary vein (2 marks)
- Artery is thicker
| - Higher pressure/more muscle
37
Explain why the thickness of the aorta wall changes all the time during each cardiac cycle (3 marks)
- Aorta wall stretches when heart contracts/systole
- Aorta wall recoils when heart relaxes/diastole
- Maintains smooth pressure
38
Describe how tissue fluid is formed and how it is returned to the circulatory system (6 marks)
Formation:
- Hydrostatic pressure
- Forces water/fluid out
- Large proteins remain in capillary
Return:
- Low water potential in capillary/blood
- Due to (plasma) proteins
- Water enters capillary/blood
- By osmosis
- Correct reference to lymph
39
In which one of the four chambers of the human heart does pressure reach the highest value (1 mark)
- Left ventricle
40
Explain how the structure of the left ventricle causes high pressure (1 mark)
- Thick walls
41
Explain what causes the maximum pressure in the ventricle to be much higher than that in the atrium (2 marks)
- Ventricle has thicker muscle
| - So the contractions are stronger
42
Explain how tissue fluid is returned to the circulatory system (3 marks)
- Hydrostatic pressure lower in capillary/blood
- Water returns
- By osmosis
- Water potential lower in blood/capillary
- Due to protein in blood
- Returns via lymph system/vessels
43
When a wave of electrical activity reaches the AVN, there is a short delay before a new wave leaves the AVN. Explain the importance of this short delay (2 marks)
- Allows atria to empty/contract
| - Before ventricles contract
44
Explain how the structures of the walls of arteries and arterioles are related to their functions (6 marks)
Elastic tissue:
- Stretches under pressure then recoils
- Evens out pressure/flow
Muscle:
- Contracts to reduce diameter of lumen
- Changes flow/pressure
Epithelium:
- Smooth
- Reduces friction/blood clots
45
Explain the importance of elastic fibres in the wall of the aorta (2 marks)
- Stretches under high pressure/during systole and recoils under low pressure/during diastole
46
Explain the importance of muscle fibres in the wall of an arteriole (2 marks)
- Muscle contracts
| - Arteriole narrows
47
Explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins (4 marks)
- Smaller mammal has greater surface area to volume ratio
- Smaller mammal has more heat lost
- Smaller mammal has greater rate of respiration
- Oxygen required for respiration so haemoglobin releases more oxygen
48
Describe how the cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN) (5 marks)
- SAN initiates heartbeat/acts as a pacemaker/
- SAN sends wave of electrical activity/impulses across atria causing atrial contraction
- AVN delays electrical activity/impulses
- Allowing atria to empty before ventricles contract
- AVN sends wave of electrical activity/impulses down
- Causing ventricles to contract from base up/ventricular systole
49
Describe and explain how an increase in respiration in the tissues of a mammal affects the oxygen dissociation curve of haemoglobin (2 marks)
- Increase in/more carbon dioxide
| - Curve moves to the right
50
Describe the role of the sinoatrial node (2 marks)
- Sends out electrical activity/impulses
| - Initiates the heartbeat/acts as a pacemaker
51
Explain how blood in a vein in the leg is returned to the heart (6 marks)
- Muscles surrounding veins contract and press on walls of vein and squeezes blood along veins
- Valves prevent backflow
- Systole/contraction of heart pumps blood through arteries into veins
- Recoil of heart muscle during diastole
- Draws blood from veins into atria
- Wide lumen little resistance/friction
52
Explain how oxygen in a red blood cell is made available for respiration in active tissues (3 marks)
- Respiration increases carbon dioxide concentration
- So it increases the rate at which oxygen is dissociated
- There's a low partial pressure of oxygen in tissues
- So oxygen diffuses from rbc to tissues
53
Give one way in which the structure of the wall of an artery is similar to the structure of the wall of a capillary (1 mark)
- Both have epithelium
54
Explain what is meant by the term partial pressure (1 mark)
- Measure of the concentration of a gas
55
Give two ways in which the total oxygen supplied to muscles during exercise is increased (2 marks)
- Increased heart rate
| - Vasodilation of arterioles
56
Describe and explain how water is exchanged between the blood and tissue fluid as blood flows along the capillary (4 marks)
- HP forces water out
- HP is “higher” than WP
- Proteins remain in blood and this increases WP
- WP is now “higher” than HP
- So water returns by osmosis
- Water moves out at arteriole end and back in (at venule end)
57
Suggest and explain some xerophytic features that leaves of a plant may have (4 marks)
- Hairs so ‘trap’ water vapour so water potential gradient decreased
- Stomata grooves to ‘trap’ water vapour so water potential gradient decreased
- Thick waxy layer so diffusion distance increased
- Waxy cuticle reduces evaporation/transpiration
- Curled leaves to ‘trap’ water vapour and so water potential gradient decreased
- Needles to reduces surface area to volume ratio
58
Suggest two reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration (2 marks)
- Water used for support
- Water used in photosynthesis
- Water used in hydrolysis
- Water produced during respiration
59
Describe the processes involved in the transport of sugars in plant stems (5 marks)
- At source sucrose is actively transported into the phloem/sieve element/tube
- By companion cells
- Lowers water potential in phloem/sieve element/tube and water enters by osmosis
- Produces high hydrostatic pressure
- Mass flow towards sink/roots
- At sink/roots sugars are removed
60
Describe how a high pressure is produced in the leaves (3 marks)
- Water potential becomes lower
- So water enters phloem by osmosis
- Increased volume of water causes increased pressure
61
Describe the mass flow hypothesis for the mechanism of translocation in plants (4 marks)
- In source/leaf sugars actively transported into phloem
- By companion cells
- This lowers water potential of sieve cell/tube and water enters by osmosis
- Increase in pressure causes mass movement towards sink/root
- Sugars used/converted in root for respiration for storage
62
Explain one way in which sieve cells are adapted for mass transport (2 marks)
- Few organelles
| - So more flow
63
Explain why the transpiration rate increases when the temperature increases (2 marks)
- Molecules have more kinetic energy
| - So faster diffusion of water
64
Give two precautions when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot (2 marks)
- Cut shoot under water
| - Ensure no air bubbles are present
65
Give two reasons why the potometer does not truly measure the rate of transpiration (2 marks)
- Water used in photosynthesis
- Water produced in respiration
- Water used to provide turgidity
66
Explain why the diameter of the trunk is smallest at midday (6 marks)
- Diameter of trunk minimal at warmest time of day
- Stomata open in light → so more water loss
- Water evaporates more when warm / more heat energy for water evaporation
- Hydrogen-bonding between water molecules/cohesion
- Adhesion between water molecules and walls of xylem vessels
- Xylem pulled inwards by faster flow of water/pulled in by tension
67
Explain how xylem tissue is adapted for its function (4 marks)
- Long cells/tubes with no end walls
- continuous water columns
- No cytoplasm / no organelles
- To obstruct flow
- Lignin
- Withstands tension/waterproof
- Pits in walls
- Allow lateral movement
68
Describe how water is moved through a plant according to the cohesion-tension hypothesis (4 marks)
- Water evaporates from leaves
- Reduces water potential in cell/water potential gradient across cells
- Water is drawn out of xylem
- Water creates tension
- Cohesive forces between water molecules
- Water pulled up as a column
69
Explain why a transpiration stream will still continue even if the cells are killed (2 marks)
- Xylem is non-living tissue
| - No energy is needed/passive process
70
Explain the advantage of xerophytic plants having sunken stomata (2 marks)
- Reduces water loss/transpiration
| - Reduced water potential gradient
71
Explain why binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind (2 mark)
- Binding of first oxygen changes tertiary structure of haemoglobin
- Uncovers another binding site
72
Explain the Bohr effect (5)
- the higher the rate of respiration, the more CO₂ produced
- this lowers ppO₂
- due to increase in carbonic acid, Hb's tertiary structure changes (due to more H+) so there is a lower affinity for O₂
- this means that Hb's shape is more loose so oxygen can be unloaded quickly at respiring muscles
- therefore the curve shifts to the right
73
Equation for cardiac output (1)
CO = stroke volume x heart rate
74
Give three reasons why organisms need a transport system (3)
- Larger animals have a smaller SA:V ratio so gas exchange via diffusion through skin is not very effective
- Most cells are far away from exchange surfaces
- Maintains diffusion gradient, bringing substances to and from cells
75
Explain why mammals have a double circulatory system (4)
- Blood flows through heart twice
- When it goes to the lungs, pressure drops and so circulation is slow
- Pumping through heart twice maintains pressure and prevents mix up of oxygenated and deoxygenated blood
- High pressure vital for effective transportation of blood around the body
76
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 (4 marks)
- Permeable membrane
- Thin / single cell thick walls which reduce diffusion distance
- Flattened endothelial cells which reduce diffusion distance
- Small diameter increase SA:V
- Narrow lumen reduces flow rate, increasing diffusion time
77
Explain how the structures of the walls of arteries, veins and capillaries are related to their functions (6 marks)
Artery:
- Thickest wall, enabling it to carry blood at high pressure
- Most elastic tissue which maintains pressure
- Muscle to control blood flow
Vein:
- Thin wall as it does not need to withstand high pressure
Capillary:
- Thin wall allowing diffusion
- Only endothelium present, allowing short diffusion pathway
All vessels:
- Have endothelium which reduces friction
78
Mammals such as a mouse and a horse are able to maintain a constant body temperature. Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse (3 marks)
Mouse
- Larger surface area to volume ratio
- More/faster heat loss
- Faster rate of respiration/metabolism releases heat (to replace heat loss)
79
Suggest why the transpiration rate increases when the air is moving as opposed to when the air is still (2 marks)
- Removes water vapour / moisture / saturated air
| - Increases water potential gradient / more diffusion / more evaporation
80
Suggest why the transpiration rate increases with a higher temperature (2 marks)
- Increases kinetic energy so water molecules move faster
| - Increases diffusion / evaporation
81
Explain why the rate of water movement through the xylem increases between 06.00 and 12.00 hours (2 marks)
- Stomata open and photosynthesis increases / transpiration increases
- More water pulled up due to cohesion between water molecules / by cohesion tension
82
Suggest why the diameter of a tree trunk is less at 12.00 hours than at 15:00 hours (2 marks)
- Water pulled up trunk / moves up at fast rate under tension
- Sticking / adhesion (between water and) walls / pulls xylem in
83
Explain the importance of elastic fibres in the wall of the aorta (2 marks)
- Stretches under high pressure / when ventricle contracts / springs back’ under low pressure / when ventricle relaxes
- Smooths blood flow / maintains blood pressure / reduces pressure surges
84
Explain the importance of muscle fibres in the wall of an arteriole (2 marks)
- (Muscle) contracts
| - (Arteriole) constricts / narrows / reduces blood flow (to capillaries)
