EXAM QUESTIONS CHAPTER 6/7

Question 1

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)

Answer 1

-Mouse has a larger SA:vol ratio than horse.
-More/faster heat loss.
-Faster rate of respiration/metabolism releases heat.

Question 2

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

Answer 2

Larger organisms have smaller SA:VOL ratio
Overcomes long diffusion parthway

Question 3

Explain how the counter-current principle allows efficient oxygen uptake in
the fish gas exchange system. (2)

Answer 3

1. Blood and water flow in opposite directions;
2. Diffusion/concentration gradient (maintained) along
   (length of) lamella/filament;

Question 4

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

Answer 4

Diaphragm (muscle) contracts and external intercostal muscles
contract;
(Causes volume increase and) pressure decrease;
Air moves down a pressure gradient

Question 5

Sunflowers are not xerophytic plants. The scientists repeated the
experiment with xerophytic plants.
Suggest and explain one way the leaf growth of xerophytic plants would be
different from the leaf growth of sunflowers in Figure 2 (2)

Answer 5

1. Low/slow growth;
2. Due to smaller number/area of stomata (for gas exchange);
   OR
3. Growth may continue at lower water potentials;
4. (Due to) adaptations in enzymes involved in
   photosynthesis/metabolic reactions;

Question 6

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

Answer 6

1. Stomata close;
2. Less carbon dioxide (uptake) for less photosynthesis/glucose
   production;

Question 7

Describe the pathway taken by an oxygen molecule from an alveolus to the
blood. (2)

Answer 7

1. (Across) alveolar epithelium;
2. Endothelium / epithelium of capillary;

Question 8

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

Answer 8

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;
6. (Causes) volume decrease and pressure increase in thoracic cavity
   (to above atmospheric, resulting in air moving out);

Question 9

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

Answer 9

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;

Question 10

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

Answer 10

Micelles contain bile salts and fatty acids/monoglycerides;
Ignore other correct components of micelles
2. Make fatty acids/monoglycerides (more) soluble (in water)
OR
Bring/release/carry fatty acids/monoglycerides to cell/lining (of the
iluem)
OR
Maintain high(er) concentration of fatty acids/monoglycerides to
cell/lining (of the ileum);
Accept lipid/fat for fatty acid/ monoglyceride
3. Fatty acids/monoglycerides absorbed by diffusion;
Reject if absorbed by 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)

Question 11

Describe the role of enzymes in the digestion of proteins in a mammal. (4)

Answer 11

(Reference to) hydrolysis of peptide bonds;
2. Endopeptidase act in the middle of protein/polypeptide
OR
Endopeptidase produces short(er) polypeptides/ increase number of ends
3. Exopeptidases act at end of protein/polypeptide
OR
Exopeptidase produces dipeptides/amino acids;
4. Dipeptidase acts on dipeptide/between two amino acids
OR
Dipeptidase produces (single) amino acids;

Question 12

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

Answer 12

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;

Question 13

Tissue fluid is formed from blood at the arteriole end of a capillary bed.
Explain how water from tissue fluid is returned to the circulatory system. (4)

Answer 13

1. (Plasma) proteins remain;
   Accept albumin/globulins/fibrinogen for (plasma)
   protein
2. (Creates) water potential gradient
   OR
   Reduces water potential (of blood);
3. Water moves (to blood) by osmosis;
4. Returns (to blood) by lymphatic system;

Question 14

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

Answer 14

1. Muscle contracts;
2. Constricts/narrows arteriole/lumen;

Question 15

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

Answer 15

) 1. Increases dissociation of oxygen;
Accept unloading/ release/reduced affinity for
dissociation
2. For aerobic respiration at the tissues/muscles/cells

Question 16

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

Answer 16

1. Contraction of ventricle(s) produces high
   blood / hydrostatic pressure;
2. (This) forces water (and some dissolved
   substances) out (of blood capillaries);