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TOPIC 3 MARK SCHEME SHIT Flashcards

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1
Q

Explain why hydrostatic pressure falls from arteriole end to venule end of capillary (1)

A

Loss of water/loss of fluid/friction against capillary lining

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2
Q

Explain why water potential of blood plasma is more negative at venule end than arteriole end of capillary (3)

A
  1. Water has left the capillary
  2. Proteins in blood too large to leave capillary
  3. Increasing/giving higher conc of blood proteins and thus wp
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3
Q

Stomata close when lights are off: explain advantage of this to the plant (2)

A
  1. Water is lost through stomata
  2. Prevents/reduces water loss
  3. Maintains water content of cells
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4
Q

Describe how proteins are digested in the human gut (4)

A
  1. Hydrolysis of peptide bonds
  2. Endopeptidases break polypeptides into smaller peptide chains
  3. Exopeptidases remove terminal amino acids
  4. Dipeptidases hydrolyse dipeptides into amino acids
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5
Q

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

A
  1. Increases dissociation of oxygen
  2. For aerobic respiration at the tissues/muscles/cells
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6
Q

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

A
  1. lowER affinity for oxygen/releases MORE oxygen/oxygen is released quickER/oxygen dissociates/unloads MORE readily
  2. to muscles/tissues/cells
  3. for high/rapid respiration
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7
Q

Explain how the shape of an [animal] is an adaptation to living in a cold environment (2)

A
  1. small SA:V ratio
  2. reduces heat loss/more heat retained
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8
Q

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. Details of breathing are NOT required (4)

A
  1. Trachea and bronchi and bronchioles
  2. Down pressure gradient
  3. Down diffusion gradient
  4. Across alveolar epithelium
  5. Across capillary endothelium/epithelium
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9
Q

One theory of translocation states that organic substances are pushed from a high pressure in the leaves to a lower pressure in the roots. Describe how a high pressure is produced in the leaves (3)

A
  1. Water potential becomes lower
  2. Water enters phloem by osmosis
  3. Increased volume (of water) causes increased pressure
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10
Q

Describe and explain the mechanism that causes forced expiration (4)

A
  1. Contraction of internal intercostal muscles
  2. Relaxation of diaphragm muscles/of external intercostal muscles
  3. Causes decrease in volume of chest/thoracic cavity
  4. Air pushed down pressure gradient
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11
Q

Explain how an asthma attack caused the drop in the mean FEV (forced expiratory volume - vol of air breathed out in 1 sec). (4)

A
  1. Muscle walls of bronchi/bronchioles contract
  2. Walls of bronchi/bronchioles secrete more mucus
  3. Diameter of airways reduced
  4. Flow of air reduced
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12
Q

Why are mitochondria in larger unicellular organisms closer to the cell-surface membrane, compared to smaller unicellular organisms where mitochondria are distributed evenly throughout the cytoplasm? (2)

A
  1. Large(r) cells have small(er) surface area to volume ratio
  2. Longer for oxygen to DIFFUSE (to mitochondria)
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13
Q

Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake (2)

A
  1. Large(r) organisms have a small(er) surface area:volume ratio OR converse
  2. Overcomes long DIFFUSION pathway/faster DIFFUSION
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14
Q

Why do fish obtain oxygen from systems developed to the outside of the body (protruding), while humans obtain oxygen from systems developed to the inside of the body (alveoli)? (2)

A
  1. Water has low(er) oxygen partial pressure/concentration (than air)
  2. So (system on outside) gives large surface area (in contact with water) OR so (system on outside) reduces diffusion distance (between water and blood)
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15
Q

Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse (3)

A

Mouse:
1. (Smaller so) larger surface area to volume ratio
2. More/faster heat loss (per gram/in relation to body size)
3. (Faster rate of) respiration/metabolism releases heat

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16
Q

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. (5)

A
  1. Micelles contain bile salts and fatty acids/monoglycerides
  2. Make fatty acids/monoglycerides (more) soluble (in water)
  3. Fatty acids/monoglycerides absorbed by diffusion
    - REJECT FACILITATED DIFFUSION
    - ignore if micelles themselves are being absorbed
  4. Triglycerides (re)formed (in cells)
    - accept chylomicrons form
  5. Vesicles move to cell membrane
    - accept exocytosis for “vesicles move”
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17
Q

The photograph shows a fire-breather creating a ball of fire. Fire-breathers do this by blowing a fine mist of paraffin oil onto a flame. Some of this mist can be inhaled and may eventually lead to fibrosis. People who have been fire-breathers for many years often find they cannot breathe out properly. Explain why. (2)

A
  1. Loss of elasticity / elastic tissue / increase in scar tissue;
    Accept elastin
  2. Less recoil;
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18
Q

Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish. (3)

A
  1. Water and blood flow in opposite directions
  2. Maintains concentration/diffusion gradient/equilibrium not reached/water always next to blood with a lower concentration of oxygen
  3. Along whole/length of gill/lamellae
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19
Q

Give two features of leaves of xerophytes (excluding SA, # of stomata and leaf thickness). Explain how each features reduces water loss. (2)

A
  1. Thick(er) cuticle
    so
    increase in diffusion
    distance / slower (rate of) diffusion;
    Feature and explanation needed for each mark.
    Reject other features not related to leaves.
    Reject features related to water storage.
    ‘Cuticle’ alone is insufficient (all leaves have a cuticle).
    Reject suggestion of ‘less’ diffusion, for idea of ‘slower diffusion’, an idea of rate is required.
  2. Hairs on leaves
    so
    reduction in air movements / increase in humidity / decrease in water potential gradient;
  3. Curled leaves
    so
    reduction in air movements / increase in humidity / decrease in water potential gradient;
  4. Sunken stomata
    so
    reduction in air movements / increase in humidity / decrease in water potential gradient.
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20
Q

Describe and explain one feature of the alveolar epithelium that makes the
epithelium well adapted as a surface for gas exchange. Do not refer to surface area or moisture in your answer. (2)

A

Mark in pairs: 1 and 2 OR 3 and 4
1. Flattened cells
OR
Single layer of cells;
Reject thin cell wall/membrane
Accept thin cells
Accept ‘one cell thick’
2. Reduces diffusion distance/pathway;
3. Permeable;
4. Allows diffusion of oxygen/carbon dioxide;
Ignore gas exchange

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21
Q

Tidal volume is the volume of air inhaled and exhaled during a single breath when a person is resting. The tidal volume in a person with emphysema is reduced compared with the tidal volume in a healthy person.
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli. (3)

A
  1. Less carbon dioxide exhaled/moves out (of lung)
    OR
    More carbon dioxide remains (in lung);
  2. (So) reduced diffusion/concentration gradient (between blood and alveoli);
  3. Less/slower movement of carbon dioxide out of blood
    OR
    More carbon dioxide stays in blood;
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22
Q

Describe and explain the mechanism that causes lungs to fill with air. (3)

A
  1. Diaphragm (muscle) contracts and external intercostal muscles contract;
    Ignore ribs move up and out
  2. (Causes volume increase and) pressure decrease;
  3. Air moves down a pressure gradient
    Ignore along
    OR
    Air enters from higher atmospheric pressure;
23
Q

Particulate matter is solid particles and liquid particles suspended in air. Polluted air contains more particulate matter than clean air.
A high concentration of particulate matter results in the death of some alveolar epithelium cells. If alveolar epithelium cells die inside the human body they are replaced by non-specialised, thickened tissue.
Explain why death of alveolar epithelium cells reduces gas exchange in human lungs. (3)

A
  1. Reduced surface area;
  2. Increased distance for diffusion;

Accept description of efficient gas exchange in
healthy alveolar epithelium as long as reference made to the damaged tissue changing this.

  1. Reduced rate of gas exchange;
24
Q

Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water grow only slowly. (2)

A
  1. Stomata close;
  2. Less carbon dioxide (uptake) for less photosynthesis/glucose production;
    ‘Less’ only required once.
    Reject ‘no photosynthesis’ but accept ‘carbon dioxide can’t enter so less photosynthesis’.
    Ignore oxygen for respiration but reject oxygen for photosynthesis.
    Ignore less water for photosynthesis.
    Accept only correct chemical formulae.
    For ‘glucose’ accept named product of photosynthesis eg triose phosphate, TP, amino acid, lipid.
25
Q

Explain how one feature of an alveolus allows efficient gas exchange to occur. (2)

A
  1. (The alveolar epithelium) is one cell thick;

Reject thin membrane

  1. Creating a short diffusion pathway / reduces the diffusion distance;
26
Q

Describe the gross structure of the human gas exchange system and how we breathe in and out. (6)

A
  1. Named structures – trachea, bronchi, bronchioles, alveoli;
    Reject mp1 if structures from other physiological systems are named but award mp2 if the correct structures are in the correct order.
  2. Above structures named in correct order
    OR
    Above structures labelled in correct positions on a diagram;
    Reject mp1 if structures from other physiological systems are named but award mp2 if the correct structures are in the correct order.
  3. Breathing in – diaphragm contracts and external intercostal muscles contract;
  4. (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in);
    For thoracic cavity accept ‘lungs’ or ‘thorax’.
    Reference to ‘thoracic cavity’ only required once.
  5. Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
    Accept diaphragm relaxes and (external) intercostal muscles relax and lung tissue elastic (so recoils).
  6. (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);
    For thoracic cavity accept ‘lungs’ or ‘thorax’.
    Reference to ‘thoracic cavity’ only required once.
    If idea of thoracic cavity is missing or incorrect,
    allow ECF for mark point 6.
27
Q

Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange. (3)

A
  1. Tracheoles have thin walls so short diffusion distance to cells;
  2. Highly branched / large number of tracheoles so short diffusion distance to cells;
  3. Highly branched / large number of tracheoles so large surface area (for gas exchange);
  4. Tracheae provide tubes full of air so fast diffusion (into insect tissues);
  5. Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;
    OR
    Fluid in the end of the tracheoles that moves out (into tissues) during exercise so larger surface area (for gas exchange);
  6. Body can be moved (by muscles) to move air so maintains diffusion / concentration gradient for oxygen / carbon dioxide;
  7. Do not accept unqualified references to thin
    membranes.
    Max 2 if any reference to blood
    Ignore references to spiracles
  8. Accept ‘water’ for fluid.
    Accept ‘cells’ and ‘tissues’ as interchangeable
    words.
28
Q

Explain two ways in which the structure of fish gills is adapted for efficient gas exchange. (2)

A
  1. Many lamellae / filaments so large surface area;
  2. Thin (surface) so short diffusion pathway;

1 & 2 must each have a feature and a consequence

29
Q

Explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills. (3)

A
  1. Water and blood flow in opposite directions;
  2. Blood always passing water with a higher oxygen concentration;
  3. Diffusion gradient maintained throughout length (of gill)
    OR
    Diffusion occurs throughout length of gill
    OR
    If water and blood flowed in same direction equilibrium would be reached;
30
Q

Describe the role of micelles in the absorption of fats into the cells lining the ileum. (3)

A
  1. Micelles include bile salts and fatty acids;
    Ignore other correct components of micelles.
  2. Make the fatty acids (more) soluble in water;
    For ‘fatty acids’ accept fats / lipids.
  3. Bring/release/carry fatty acids to cell/lining (of the ileum);

For ‘fatty acids’ accept fats/lipids.

  1. Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
  2. Fatty acids (absorbed) by diffusion;

Reject if absorbed by facilitated diffusion
Ignore if micelles themselves are being absorbed.
Ignore references to monoglycerides.

31
Q

Explain the advantages of lipid droplet and micelle formation. (3)

A
  1. Droplets increase surface areas (for lipase / enzyme action);
  2. (So) faster hydrolysis / digestion (of triglycerides / lipids);
  3. Micelles carry fatty acids and glycerol /
    monoglycerides to / through membrane / to
    (intestinal epithelial) cell;
  4. Context is important
  5. Reject micelles increase surface area
  6. Ignore ‘breakdown’
  7. Ignore ‘small enough’
  8. Accept description of membrane
  9. Reject any movement through membrane
    proteins
31
Q

How is the Golgi involved in the absorption of lipids? (3)

A
  1. Modifies / processes triglycerides;
  2. Combines triglycerides with proteins;
  3. Packaged for release / exocytosis
    OR
    Forms vesicles;
    Ignore ‘processes and packages’ unqualified
  4. Reject synthesises triglycerides
  5. Accept ‘forms / are lipoproteins’
32
Q

Explain how the pressure in the ventricle is related to blood flow in the aorta (2)

A
  1. Ventricle pressure rises THEN blood starts to flow into aorta because pressure causes (aortic/semilunar) valve to open
  2. Ventricle pressure starts to fall SO blood falls
33
Q

Explain how pressure in the ventricle is related to thickness of the ventricle wall (2)

A
  1. Thickness of wall increases BECAUSE ventricle (wall) contracts
  2. Contraction CAUSES increase in pressure
34
Q

Explain how hypertension leads to accumulation of tissue fluid (3)

A
  1. High blood pressure = high hydrostatic pressure
  2. Increases outward pressure from (arterial) end of capillary/reduces inward pressure at (venule) end of capillary
  3. (So) more tissue fluid formed/less tissue fluid is reabsorbed.

Allow lymph system unable to drain tissues fast enough

35
Q

Other than causing slow blood flow, explain two advantages of capillaries being narrow (2)

A
  1. Short pathway / short distance between blood and outside of capillary
  2. Large SA (of blood) in contact with walls of capillaries
  3. Fast exchange / fast diffusion / fast osmosis
36
Q

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

A

Width / size / diameter of blood cell

37
Q

Suggest why the aorta has a greater rise and fall in blood pressure compared to small arteries (3)

A
  1. Aorta is close / directly linked to the heart / ventricle / pressure is higher / is high
  2. (Aorta has) elastic tissue
  3. (Aorta has) stretch / recoil
38
Q

Explain how cardiac output can remain the same even when resting heart rate has decreased (2)

A
  1. cardiac output = stroke volume x heart rate
  2. stroke volume increases
39
Q

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

A
  1. (Plasma) proteins remain
  2. (Creates) water potential gradient / reduces water potential (of blood)
  3. Water moves (to blood) via osmosis
  4. Returns (to blood) by lymphatic system
40
Q

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

A
  1. Muscle contracts
  2. Constricts / narrows arteriole / lumen
41
Q

Which blood vessel carries blood at the lowest pressure?

A

VENA CAVA NOT CAPILLARIES

42
Q

An increase in exercise intensity produces an increase in volume of CO2 produced. However, pCO2 breathed out in experiment didn’t show a large increase. Suggest ONE physiological change that would cause this, and explain how it would allow for the removal of the increase in vol CO2 produced. (2)

A
  1. Increase in breathing (rate)
  2. Similar/same pCO2 per breath, but more breaths
    OR
  3. Increase in tidal volume
  4. Similar/same pCO2 per breath, but increased volume per breath
43
Q

EPO is a performance enhancing drug that increases % of RBCs in blood. Suggest how overuse of EPO can increase risk of heart attack (2)

A
  1. EPO causes blood to thicken
  2. Could block coronary arteries/slows blood flow/could cause clots
44
Q

Describe & explain effect of increasing [CO2] on dissociation of oxyhaemoglobin (2)

A
  1. Increases/more oxygen dissociation/unloading OR decreases haemoglobin’s affinity for O2
  2. (By) decreasing (blood) pH/increasing acidity
45
Q

Explain how AV valves maintain a unidirectional flow of blood (2)

A
  1. Pressure in atrium higher than in ventricle causing valve to open
  2. Pressure in ventricle is higher than in atrium causing valve to close
46
Q

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

A
  1. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin
  2. Create / leads to / uncovers second / another binding site
47
Q

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

A
  1. Contraction of ventricle(s) produces HIGH blood/hydrostatic pressure
  2. (This) forces water (and some dissolved substances) out (of blood capillaries)
48
Q

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

A
  1. In source/leaf, sugars actively transported into phloem
  2. By companion cells
  3. Lowers water potential of sieve cell/tube and water enters by osmosis
  4. Increase in pressure causes mass movement (towards sink/root)
  5. Sugars used/converted in root for respiration for storage (accept starch)
49
Q

One theory of translocation states that organic substances are pushed form a high pressure in the leaves to a lower pressure in the roots. Describe how a high pressure is produced in the leaves (4)

A
  1. Sucrose actively transported
  2. Water potential becomes lower
  3. Water enters phloem by osmosis
  4. Increased volume (of water) causes increased pressure
50
Q

Use your understanding of transpiration and mass flow to explain why phloem pressure is reduced during the hottest part of the day (3)

A
  1. High (rate of) transpiration/evaporation
  2. Water lost through stomata / (high) tension in xylem
  3. (Causes) less water movement from xylem to phloem / insufficient WP in phloem to draw water from xylem
51
Q

Explain why water moves up the xylem (3)

A
  1. Water evaporates/is transpired
  2. Water potential gradient/lower WP creates tension/pulls up water
    Accept negative pressure for tension
  3. Hydrogen bonds/cohesion/adhesion maintains column
52
Q

Describe the cohesion-tension theory of water transport in the xylem (5)

A
  1. Water lost from leaf due to transpiration/evaporation/diffusion from mesophyll/leaf cells
  2. Lowers WP of mesophyll/leaf cells
  3. Water pulled up xylem
  4. Water molecules cohere/“stick” together by hydrogen bonds
  5. (forming continuous) water column
  6. Adhesion of water to walls of xylem

Biology (42 decks)

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