Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AQA AS Biology > Section 3 - Unit 7: Mass Transport > Flashcards

Section 3 - Unit 7: Mass Transport Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the path by which oxygen goes from an alveolus to the blood (2 marks)

A
  • Through alveolar epithelium

- Through capillary epithelium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

State two ways in which blood plasma is different from tissue fluid (2 marks)

A
  • Larger proteins

- More glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Explain how the left ventricle causes the blood to be at high pressure (1 mark)

A
  • It contracts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Suggest how widening of blood vessels can reduce ventricular blood pressure (2 marks)

A
  • Larger lumen

- This reduces blood pressure (less friction)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

State which blood vessel carries oxygenated blood away from the heart (1 mark)

A
  • Aorta
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

State which blood vessel carries deoxygenated blood to the heart (1 mark)

A
  • Vena Cava
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Explain how the highest blood pressure is produced in the left ventricle (1 mark)

A
  • Strongest/stronger contractions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain how tissue fluid is formed (2 marks)

A
  • Outward pressure of 3.2 kPa

- Forces small molecules out of capillary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Explain the function of the coronary arteries (2 marks)

A
  • Carries oxygen/glucose

- To heart muscle/tissues/cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Other than causing slow blood flow, explain one advantage of capillaries being narrow (1 mark)

A
  • Fast diffusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What factor limits the minimum internal diameter of the lumen of a capillary (1 mark)

A
  • Diameter of blood cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Explain the advantage of the oxygen dissociation curve for haemoglobin shifting to the right during vigorous exercise (3 marks)

A
  • Lower affinity for oxygen
  • Faster unloading to muscles/tissues/cells
  • For rapid respiration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

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)

A
  • 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

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)

A
  • Higher affinity/partial pressure

- So oxygen moves from mother to fetus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Name the blood vessel to which an artificial heart is connected (1 mark)

A
  • Aorta
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Suggest why the artificial heart mainly helps the left ventricle and not the right ventricle (2 marks)

A
  • Left ventricle pumps to whole body

- So it does most work/produces a greater pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Suggest why the pulse felt can be used to measure heart rate (2 marks)

A
  • The pulse is caused by pressure

- From one contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Explain why an arteriole is described as an organ (1 mark)

A
  • Made up of more than one tissue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Explain how muscle fibres in an arteriole reduce blood flow to capillaries (2 marks)

A
  • The muscle contracts

- And narrows the capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Give the advantage of blood flow in capillaries being slow (1 mark)

A
  • More time for exchange of substances
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Explain why a lack of protein in the blood causes a build up of tissue fluid (3 marks)

A
  • Water potential in capillary not as low
  • So no water removed into capillary
  • By osmosis, causing the build up of tissue fluid
35
Q

Explain why the values for the pressure in the xylem are negative (1 mark)

A
  • Inside xylem lower than atmospheric pressure
36
Q

Explain the difference in thickness between the pulmonary artery and the pulmonary vein (2 marks)

A
  • Artery is thicker

- Higher pressure/more muscle

37
Q

Explain why the thickness of the aorta wall changes all the time during each cardiac cycle (3 marks)

A
  • Aorta wall stretches when heart contracts/systole
  • Aorta wall recoils when heart relaxes/diastole
  • Maintains smooth pressure
38
Q

Describe how tissue fluid is formed and how it is returned to the circulatory system (6 marks)

A

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
Q

In which one of the four chambers of the human heart does pressure reach the highest value (1 mark)

A
  • Left ventricle
40
Q

Explain how the structure of the left ventricle causes high pressure (1 mark)

A
  • Thick walls
41
Q

Explain what causes the maximum pressure in the ventricle to be much higher than that in the atrium (2 marks)

A
  • Ventricle has thicker muscle

- So the contractions are stronger

42
Q

Explain how tissue fluid is returned to the circulatory system (3 marks)

A
  • 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
Q

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)

A
  • Allows atria to empty/contract

- Before ventricles contract

44
Q

Explain how the structures of the walls of arteries and arterioles are related to their functions (6 marks)

A

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
Q

Explain the importance of elastic fibres in the wall of the aorta (2 marks)

A
  • Stretches under high pressure/during systole and recoils under low pressure/during diastole
46
Q

Explain the importance of muscle fibres in the wall of an arteriole (2 marks)

A
  • Muscle contracts

- Arteriole narrows

47
Q

Explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins (4 marks)

A
  • 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
Q

Describe how the cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN) (5 marks)

A
  • 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
Q

Describe and explain how an increase in respiration in the tissues of a mammal affects the oxygen dissociation curve of haemoglobin (2 marks)

A
  • Increase in/more carbon dioxide

- Curve moves to the right

50
Q

Describe the role of the sinoatrial node (2 marks)

A
  • Sends out electrical activity/impulses

- Initiates the heartbeat/acts as a pacemaker

51
Q

Explain how blood in a vein in the leg is returned to the heart (6 marks)

A
  • 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
Q

Explain how oxygen in a red blood cell is made available for respiration in active tissues (3 marks)

A
  • 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
Q

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)

A
  • Both have epithelium
54
Q

Explain what is meant by the term partial pressure (1 mark)

A
  • Measure of the concentration of a gas
55
Q

Give two ways in which the total oxygen supplied to muscles during exercise is increased (2 marks)

A
  • Increased heart rate

- Vasodilation of arterioles

56
Q

Describe and explain how water is exchanged between the blood and tissue fluid as blood flows along the capillary (4 marks)

A
  • 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
Q

Suggest and explain some xerophytic features that leaves of a plant may have (4 marks)

A
  • 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
Q

Suggest two reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration (2 marks)

A
  • Water used for support
  • Water used in photosynthesis
  • Water used in hydrolysis
  • Water produced during respiration
59
Q

Describe the processes involved in the transport of sugars in plant stems (5 marks)

A
  • 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
Q

Describe how a high pressure is produced in the leaves (3 marks)

A
  • Water potential becomes lower
  • So water enters phloem by osmosis
  • Increased volume of water causes increased pressure
61
Q

Describe the mass flow hypothesis for the mechanism of translocation in plants (4 marks)

A
  • 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
Q

Explain one way in which sieve cells are adapted for mass transport (2 marks)

A
  • Few organelles

- So more flow

63
Q

Explain why the transpiration rate increases when the temperature increases (2 marks)

A
  • Molecules have more kinetic energy

- So faster diffusion of water

64
Q

Give two precautions when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot (2 marks)

A
  • Cut shoot under water

- Ensure no air bubbles are present

65
Q

Give two reasons why the potometer does not truly measure the rate of transpiration (2 marks)

A
  • Water used in photosynthesis
  • Water produced in respiration
  • Water used to provide turgidity
66
Q

Explain why the diameter of the trunk is smallest at midday (6 marks)

A
  • 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
Q

Explain how xylem tissue is adapted for its function (4 marks)

A
  • 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
Q

Describe how water is moved through a plant according to the cohesion-tension hypothesis (4 marks)

A
  • 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
Q

Explain why a transpiration stream will still continue even if the cells are killed (2 marks)

A
  • Xylem is non-living tissue

- No energy is needed/passive process

70
Q

Explain the advantage of xerophytic plants having sunken stomata (2 marks)

A
  • Reduces water loss/transpiration

- Reduced water potential gradient

71
Q

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

A
  • Binding of first oxygen changes tertiary structure of haemoglobin
  • Uncovers another binding site
72
Q

Explain the Bohr effect (5)

A
  • 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
Q

Equation for cardiac output (1)

A

CO = stroke volume x heart rate

74
Q

Give three reasons why organisms need a transport system (3)

A
  • 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
Q

Explain why mammals have a double circulatory system (4)

A
  • 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
Q

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)

A
  • 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
Q

Explain how the structures of the walls of arteries, veins and capillaries are related to their functions (6 marks)

A

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
Q

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)

A

Mouse

  • Larger surface area to volume ratio
  • More/faster heat loss
  • Faster rate of respiration/metabolism releases heat (to replace heat loss)
79
Q

Suggest why the transpiration rate increases when the air is moving as opposed to when the air is still (2 marks)

A
  • Removes water vapour / moisture / saturated air

- Increases water potential gradient / more diffusion / more evaporation

80
Q

Suggest why the transpiration rate increases with a higher temperature (2 marks)

A
  • Increases kinetic energy so water molecules move faster

- Increases diffusion / evaporation

81
Q

Explain why the rate of water movement through the xylem increases between 06.00 and 12.00 hours (2 marks)

A
  • Stomata open and photosynthesis increases / transpiration increases
  • More water pulled up due to cohesion between water molecules / by cohesion tension
82
Q

Suggest why the diameter of a tree trunk is less at 12.00 hours than at 15:00 hours (2 marks)

A
  • Water pulled up trunk / moves up at fast rate under tension
  • Sticking / adhesion (between water and) walls / pulls xylem in
83
Q

Explain the importance of elastic fibres in the wall of the aorta (2 marks)

A
  • 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
Q

Explain the importance of muscle fibres in the wall of an arteriole (2 marks)

A
  • (Muscle) contracts

- (Arteriole) constricts / narrows / reduces blood flow (to capillaries)

AQA AS Biology (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions