Exam Questions by Topic Chapter 3 Biology

Question 1

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

Answer 1

1) Larger organisms have a smaller surface area to volume ratio.
2) Specialised systems allow for faster diffusion.

Question 2

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

Answer 2

1) Mouse has a larger surface area to volume ratio.
2) So the mouse has faster heat loss.
3) So faster rate of respiration.

Question 3

Describe the relationship between size and surface area to volume ratio of organisms. (1)

Answer 3

1) As size increases, surface area to volume ratio decreases.

Question 4

Explain why oxygen uptake is a measure of metabolic rate in organisms. (1)

Answer 4

1) Oxygen is used in respiration which provides energy.

Question 5

Describe and explain two features 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.

Answer 5

1) Single layer of cells.
2) Reduces diffusion distance.

1) Permeable
2) Allows diffusion of oxygen and carbon dioxide.

Question 6

Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli. (3)

Answer 6

1) Less carbon dioxide moves out of the lungs.
2) So reduced concentration gradient.
3) More carbon dioxide stays in the blood.

Question 7

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

Answer 7

1) Blood and water flow in opposite directions.
2) Concentration gradient maintained along length of lamella.

Question 8

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

Answer 8

1) Diaphragm contracts and EIM contract.
2) Causes a volume increase and pressure decrease.
3) Air moves down a pressure gradient.

Question 9

Explain why death of alveolar epithelium cells reduces gas exchange in human lungs. (3)

Answer 9

1) Reduced surface area.
2) Increased diffusion distance.
3) Reduced rate of gas exchange.

Question 10

Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. (3)

Answer 10

1) Water and blood flow in opposite directions.
2) Maintains a diffusion gradient of oxygen.
3) Diffusion along whole length of lamellae.

Question 11

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

Answer 11

1) Stomata close
2) Less carbon dioxide uptake for less photosynthesis.

Question 12

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

Answer 12

1) Across alveolar epithelium.
2) Across epithelium of capillary.

Question 13

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

Answer 13

1) Alveolar epithelium is one cell thick.
2) Reducing the diffusion distance.

Question 14

Describe the gross structure of the human gas exchange system and how we breathe in and out. (5)

Answer 14

1) Trachea, bronchi, bronchioles and alveoli.
2) Breathing in - diaphragm contracts and EIM contract.
3) Causes volume increase and pressure decrease in thoracic cavity.
4) Breathing out - diaphragm relaxes and IIM contract
5) Causes volume decrease and pressure increase in thoracic cavity.

Question 15

Explain four ways in which an insect’s tracheal system is adapted for efficient gas exchange.

Answer 15

1) Tracheoles have thin walls so short diffusion distance to cells.
2) Highly branched tracheoles so large surface area.
3) Tracheae provide tubes full of air so fast diffusion.
4) Fluid in the end of tracheoles that moves out during exercise so larger surface area.

Question 16

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

Answer 16

1) Many lamellae so large surface area.
2) Thin surface so short diffusion pathway.

Question 17

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

Answer 17

1) Micelles contain bile salts and fatty acids.
2) Brings fatty acids and monoglycerides to lining of ileum.
3) Fatty acids and monoglycerides absorbed by diffusion.
4) Triglycerides reformed in cells.
5) Vesicles move to cell membrane.

Question 18

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

Answer 18

1) Micelles include bile salts and fatty acids.
2) Bring fatty acids to lining of ileum.
3) Fatty acids are absorbed by diffusion.

Question 19

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

Answer 19

1) Hydrolysis of peptide bonds.
2) Endopeptidases act in the middle of the polypeptide.
3) Exopeptidases act at the end of the polypeptide.
4) Dipeptidases act between two amino acids.

Question 20

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

Answer 20

1) Droplets increase surface area for lipase action.
2) So faster hydrolysis of lipids.
3) Micelles carry fatty acids and glycerol to cell.

Question 21

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

Answer 21

1) Modifies triglycerides.
2) Combines triglycerides with proteins.
3) Forms vesicles.

Question 22

Cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how. (3)

Answer 22

1) Sodium ions actively transported from ileum cell to blood
2) Maintains diffusion gradient for sodium to enter cells from gut.
3) Glucose enters by facilitated diffusion with sodium ions.

Question 23

Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. (3)

Answer 23

1) Renal vein
2) Vena cava to right atrium
3) Right ventricle to pulmonary artery.

Question 24

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

Answer 24

1) Plasma proteins remain
2) Creates water potential gradient.
3) Water moves to blood by osmosis.
4) Returns to blood by lymphatic system.

Question 25

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

Answer 25

1) Muscle contracts 2) Vasoconstriction - constricts lumen.

Question 26

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

Answer 26

1) Increases dissociation of oxygen. 2) For aerobic respiration at the tissues.

Question 27

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin. (2)

Answer 27

1) Increased dissociation 2) By increased acidity

Question 28

Explain how the atrioventricular valve maintains a unidirectional flow of blood. (2)

Answer 28

1) Pressure in left atrium is higher than pressure in left ventricle causing the valve to open. 2) Pressure in left ventricle is higher than pressure in left ventricle causing the valve to close.

Question 29

Name the blood vessels that carry blood to the heart muscle (1)

Answer 29

1) Coronary arteries

Question 30

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

Answer 30

1) Binding of first oxygen changes the tertiary structure of the protein. 2) Uncovers another binding site.

Question 31

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

Answer 31

1) Contraction of ventricles produces hydrostatic pressure. 2) This forces water out of blood capillaries.

Question 32

Lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system. Suggest how a blockage in the lymphatic system could cause lymphoedema. (1)

Answer 32

1) Excess tissue fluid builds up.

Question 33

Explain how changes in the shape of haemoglobin result in the S-shaped (sigmoid) oxyhaemoglobin dissociation curve for HbA. (2)

Answer 33

1) First oxygen binds to haemoglobin causing the tertiary structure to change shape. 2) This allows more oxygen to bind easily.

Question 34

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

Answer 34

Loss of water.

Question 35

High blood pressure leads to an accumulation of tissue fluid. Explain how. (3)

Answer 35

1) High blood pressure = high hydrostatic pressure. 2) Increases outward pressure from arterial end of capillary. 3) So more tissue fluid is formed.

Question 36

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

Answer 36

1) Trachea, bronchi and bronchioles. 2) Down pressure gradient. 3) Across alveolar epithelium 4) Across capillary endothelium.

Question 37

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

Answer 37

1) Oxygen unloads more readily. 2) To muscles 3) For rapid respiration.

Question 38

Explain how a large animal is adaptated to living in a cold environment. (2)

Answer 38

1) Smaller surface area to volume ratio. 2) More heat is retained.

Question 39

Give two features of leaves of xerophytes. For each feature explain how it reduces water loss (2)

Answer 39

1) Thicker leaves so greater diffusion distance for water. 2) Smaller surface area so less evaporation.

Question 40

The stomata close when the light is turned off. Explain the advantage of this to the plant. (2)

Answer 40

1) Water is lost through stomata. 2) Closure prevents water loss.

Question 41

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

Answer 41

1) Short distance between blood and outside of capillary.