3 Exam Questions

Question 1

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

Answer 1

Larger animals have smaller surface area to volume ratio
Takes longer for oxygen to diffuse due to longer diffusion pathway

Question 2

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]

Answer 2

Mouse is smaller so larger surface area to volume ratio
More heat loss
Faster rate of respiration to release heat

Question 3

Describe the relationship between size and surface area to volume ratio of organisms. [1]

Answer 3

As size increases, ratio decreases

Question 4

Explain why oxygen uptake is a measure of metabolic rate in organisms. [1]

Answer 4

Oxygen is used in respiration which is a metabolic process

Question 5

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

Answer 5

Less carbon dioxide exhaled
Reduced concentration gradient between blood and alveoli
Less movement of carbon dioxide out of blood

Question 6

Explain how the counter-current principle allows efficient oxygen uptake in the fish gas exchange system. [3]

Answer 6

Blood and water flow in opposite directions
Maintains concentration gradient of oxygen
Diffusion along length of lamellae

Question 7

Describe and explain the mechanism that causes lungs to fill with air. [3]

Answer 7

Diaphragm and external intercostal muscles contract
Causes volume increase and pressure decrease
Air moves down pressure gradient from higher atmospheric pressure into lungs

Question 8

Explain why death of alveolar epithelium cells reduces gas exchange in human lungs. [3]

Answer 8

Reduced surface area
Increased distance for diffusion
Reduced rate of gas exchange

Question 9

Suggest and explain one way the leaf growth of xerophytic plants would be different from others. [2]

Answer 9

Slower growth
Due to smaller number of stomata for gas exchange

Question 10

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

Answer 10

Stomata close
Less carbon dioxide uptake so less photosynthesis and less glucose produced

Question 11

Describe the pathway taken by an oxygen molecule from an alveolus to the blood. [2]

Answer 11

Across alveolar epithelium
Epithelium of capillary

Question 12

Explain how one feature of an alveolus allows for efficient gas exchange to occur. [2]

Answer 12

The alveolar epithelium is one cell thick
Creating a short diffusion pathway

Question 13

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

Answer 13

Trachea, bronchi, bronchioles, alveoli

Breathing in - diaphragm and external intercostal muscles contract
Causes volume increase and pressure decrease in thoracic cavity to below atmospheric pressure so air moves in

Breathing out - diaphragm relaxes and internal intercostal muscles contract
Causes volume decrease and pressure increase in thoracic cavity to above atmospheric pressure so air moves out

Question 14

Explain three ways in which an insects tracheal system is adapted for efficient gas exchange. [3]

Answer 14

Tracheoles have thin walls so short diffusion distance to cells
Large number of highly branched tracheoles so large surface area for gas exchange
Large number of highly branched tracheoles so short diffusion distance to cells

Question 15

Explain three ways in which an insects tracheal system is adapted for efficient gas exchange. [3]

Answer 15

Tracheoles have thin walls so short diffusion distance to cells
Large number of highly branched tracheoles so large surface area for gas exchange
Large number of highly branched tracheoles so short diffusion distance to cells

Question 16

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

Answer 16

Many lamellae so large surface area
Thin surface so short diffusion pathway

Question 17

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]

Answer 17

Water and blood flow in opposite directions
Blood always passing water that has higher oxygen concentration
Concentration gradient maintained though length of gill for diffusionc

Question 18

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

Answer 18

Micelles contain bile salts and fatty acids
Maintain higher concentration of fatty acids in lining of ileum
Fatty acids absorbed by diffusion
Triglycerides reformed in cells
Vesicles move to cell membrane

Question 19

The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum.

Explain how. [2]

Answer 19

Maintains a concentration gradient for Na+ between ileum and cell
Na+ moves in by cotransport/facilitated diffusion bringing glucose with it

Question 20

Describe the role of micelles in the absorption of fats into the cells lining the ileum. [3]

Answer 20

Micelles include bile salts and fatty acids
Release fatty acids into lining of the ileum
Maintain higher concentration gradient for diffusion

Question 21

Describe the role of enzymes in the digestion of proteins in a mammal. [4]

Answer 21

Hydrolysis of peptide bonds
Endopeptidase acts in middle of protein to produce shorter polypeptide
Exopeptidase acts at end of protein to produce dipeptides
Dipeptidase acts on dipeptides to produce amino acids

Question 22

Explain the advantages of lipid droplet and micelle formation. [3]

Answer 22

Droplets increase surface area for lipase action
So faster hydrolysis of lipids into fatty acids and glycerol
Micelles carry fatty acids and glycerol through membrane to epithelial cell

Question 23

Suggest how the golgi is involved in the absorption of lipids. [3]

Answer 23

Modifies/processes triglycerides
Combines triglycerides with proteins
Packaged into vesicles for exocytosis

Question 24

Cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions.

Explain how. [3]

Answer 24

Sodium ions actively transported from ileum cell to blood
Maintains diffusion gradient for sodium to enter cells from gut
Glucose enters by facilitated diffusion with sodium ions;

Question 25

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

Do not include descriptions of pressure changes in the heart or the role of heart valves in your answer.

Answer 25

Renal vein
Vena cava to right atrium
Right ventricle to pulmonary artery

Question 26

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 26

Plasma proteins remain
Reduces water potential of blood creating water potential gradient
Water moves into blood by osmosis
Returns to blood by lympathic system

Question 27

Describe two precautions the student should take when clearing away after a dissection. [2]

Answer 27

Hold handle when carrying and washing sharp instruments
Disinfect instruments/surfaces

Question 28

Explain how an arteriole can reduce the blood flow into capillaries. [2]

Answer 28

Muscle contracts
Narrows arteriole

Question 29

Describe the advantage of the Bohr effect during intense exercise. [3]

Answer 29

Increases dissociation of oxygen
For aerobic respiration in muscles
Less lactate at tissues due to less anaerobic respiration

Question 30

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin. [2]

Answer 30

More oxygen dissociation
By decreasing blood pH

Question 31

Give two safety precautions that should be followed when dissecting a heart. [2]

Answer 31

Wash hands/wear gloves
Disinfect equipment

Question 32

Explain how the atrioventricular valve maintains a unidirectional flow of blood. [2]

Answer 32

Pressure in left atrium is hugher than in ventricle causing valve to open
Pressure in left venticule is higher than in atrium causing value to close

Question 33

Name the blood vessels that carry blood to the heart muscle. [1]

Answer 33

Coronary arteries

Question 34

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.

Explain why. [2]

Answer 34

Binding of first oxygen changes tertiary structure of haemoglobin
Uncovers another iron for next oxygen to bind to

Question 35

Explain the role of the heart in the formation of tissue fluid. [2]

Answer 35

Contraction of ventricles produces high hydrostatic pressure in blood
Forces water and dissolved substances out of blood capillaries

Question 36

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 36

Excess tissue fluid cannot be reabsorbed so builds up

Question 37

The mass flow hypothesis is used to explain the movement of substances through phloem.

Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube. [3]

Answer 37

Sucrose actively transported into phloem
Lowering water potential
Water moves into phloem by osmosis from xylem

Question 38

Describe how a student
should ensure tjeu handled the scalpel safely during a procedure. [2]

Answer 38

Cut away from body
Against flat surface

Question 39

Suggest how a plant is able to survive without xylem tissue. [1]

Answer 39

Short diffusion pathway

Question 40

Describe the cohesion-tension theory of water transport in the xylem. [6]

Answer 40

Water lost from leaf because of transpiration
Lowers water potential of leaf cells
Water pulled up xylem creating tension
Water molecules cohere by hydrogen bonds
Forms continuous water column
Adhesion of water molecules to walls of xylem

Question 41

The student wanted to determine the rate of water loss per mm2 of surface area of the leaves of a shoot.

Outline a method she could have used to find this rate. You should assume that all water loss from the shoot is from the leaves. [3]

Answer 41

Calculate area by drawing round each leaf on graph paper and counting squares
Of both sides of each leaf
Divide rate of water loss by total surface area of leaves

Question 42

The rate of water movement through a shoot in a potometer may not be the same as the rate of water movement through the shoot of a whole plant.

Suggest one reason why. [1]

Answer 42

Plant has roots

Question 43

Describe the mass flow hypothesis for the mechanism of translocation in plants. [5]

Answer 43

Sucrose in leaf/source actively transported into phloem
By companion cells
Lowers water potential of sieve cell and water ends by osmosis
Increae in pressure causes mass movement towards sink/root
Sugars used by root for respiration