Topic 3- exchange in organisms

Question 1

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

Answer 1

1. Larger animals have a smaller surface area to volume ratio.
   OR smaller animals have a larger surface area to volume ratio.
2. Overcomes long diffusion pathway
   OR faster diffusion

Question 2

Suggest how the environment conditions have resulted adaptations of animals having oxygen uptake through a system on the outside of the body (e.g. gills) rather than an oxygen uptake system on the inside of their body (human lungs).
(2 Marks)

Answer 2

1. water has lower oxygen partial pressure than air.
2. So systems on the outside of the body gives a large surface area in contact with the water
   OR so the system on the outside decreases diffusion distance between water and blood.
3. Water is denser than air.
4. So water supports the system/ gills.

Question 3

Mammals such as a mouse and a horse are able to maintain a constant body temperature.
Using your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse.
(3 Marks)

Answer 3

1. Mice are smaller so they have a larger surface area to volume ratio.
2. More/faster heat loss in relation to body size.
3. Faster rate of respiration/ metabolism releases heat.

Question 4

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

Answer 4

1. Oxygen is used in respiration, which is a metabolic process
   OR Oxygen is used in respiration which provides energy/ ATP

Question 5

Describe and explain one feature of alveolar epithelium that makes the epithelium a well adapted surface for gas exchange.
DO NOT refer to surface are or moisture in the answer.
(2 Marks)

Answer 5

1. Flattened cells
   OR single layer of cells
2. Reduces diffusion pathway
3. Permeable
4. So allows diffusion of oxygen/ carbon dioxide

Question 6

Suggest and explain how reduced tidal volume will affect the exchange of carbon dioxide between blood and the alveoli.
(3 Marks)

Answer 6

1. Less carbon dioxide is exhaled
   OR more carbon dioxide stays in the lung.
2. Reduced concentration gradient between the blood and alveoli.
3. Less/ slower diffusion of carbon dioxide out of the blood.
   OR 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 Marks)

Answer 7

1. Blood and water flow in opposite directions.
2. Concentration gradient is maintained along the length of the lamella/ filament.

Question 8

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

Answer 8

1. Diaphragm contracts and external intercostal muscles contract.
2. Causing volume to increase and pressure to decrease.
3. Air moves down a pressure gradient.

Question 9

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

Answer 9

1. Water and blood flow in opposite directions.
2. Maintaining a concentration gradient of oxygen.
   3.Diffusion across the length go the filament/ lamella.

Question 10

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

Answer 10

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

Question 11

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

Answer 11

1. Across alveoli epithelium.
2. Endothelium/ epithelium of capillary.

Question 12

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

Answer 12

1. Named structures; trachea, alveoli, bronchi, and bronchioles.
2. Structures named in the correct order.
3. Breathing in; diaphragm contracts and external intercostal muscles contract.
4. Causes volume to increase and pressure to decrease in thoracic activity
5. Breathing out; diaphragm relaxes internal intercostal muscles contract
6. Causes volume to decrease and pressure to increase in thoracic activity.

Question 13

Give three ways in which an insects tracheal system is adapted for efficient gas exchange.
(3 Marks)

Answer 13

1. Tracheals have thin walls so thin diffusion distance to cells.
2. Highly branched so short diffusion distance to cells.
3. Highly branched to large surface area for gas exchange.
4. Trachea has tubes full of air so fast diffusion into insect tissues.
5. Fluid at the end of tracheoles that moves out and into tissue during exercise so faster diffusion through the air to the gas exchange surface.
6. Body can be moved by muscles to move air in so maintains concentration gradient for oxygen.

Question 14

Give two ways in which fish gills are adapted for efficient gas exchange.
(2 Marks)

Answer 14

1. Many lamella/ filaments providing a large surface area.
2. Thin surface so short diffusion pathway.

Question 15

Describe the process involved in the absorption and transport of lipid molecules from the ileum to the lymph vessels.
(5 Marks)

Answer 15

1. Micelles contain bile salts and fatty acids.
2. Make fatty acids more soluble in water.
3. Fatty acids are absorbed by diffusion.
4. Triglycerides reform in cells.
5. Vesicles move to cell membrane.

Question 16

The movement of sodium ions out of the cell allows the absorption of glucose into the cell lining the ileum.
Explain how.
(2 Marks)

Answer 16

1. Maintains a concentration gradient for sodium ions from ileum into cell.
2. Sodium ions moving in by facilitated diffusion brings glucose in with it.
   OR sodium ions move in by co-transport and brings glucose with it.

Question 17

Describe the role of micelles in absorbing fats into the cell lining the ileum.
(3 Marks)

Answer 17

1. Micelles include bile salts and fatty acids.
2. Make the fatty acids more soluble in water.
3. Bring fatty acids to the cell/lining of the ileum.
4. Maintains a higher concentration of fatty acids to the cell/lining the ileum.
5. Fatty acids are absorbed by diffusion.

Question 18

Describe the role of enzymes in digesting proteins in mammal.
(4 Marks)

Answer 18

1. Hydrolysis of polypeptides.
2. Endopeptidase acts in the middle of the protein/ polypeptide.
   OR endopeptidase produces shorter polypeptides.
3. Exopeptidase act on the end of a protein/ peptide.
   OR exopeptidase produce dipeptides/ amino acids.
4. Dipeptidases act of dipeptides/ between two amino acids.
   OR Dipeptidases produce single amino acids.

Question 19

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

Answer 19

1. Droplets increase surface area for lipase/ enzyme action.
2. So faster hydrolysis/ digestion of triglycerides/ lipids.
3. Micelles carry fatty acids and glycerol through membrane to intestine epithelial cell.

Question 20

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

Answer 20

1. Sodium ions are actively transported from the ileum cell to the blood.
2. This forms a diffusion gradient for sodium to enter the cell from the gut and bring glucose with it.
3. Glucose enters with the sodium through facilitated diffusion.

Question 21

Give the pathway a red blood cell takes when ravelling in the human circulatory system from a kidney to the lungs.
DO NOT include descriptions of pressure change in the heart or the role of heart valves.
(3 Marks)

Answer 21

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

Question 22

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

Answer 22

1. Plasma proteins remain
2. Creating water potential gradient
   OR reduces water potential of blood.
3. Water moves to blood by osmosis.
4. Returns to blood by the lymphatic system.

Question 23

Explain how an arteriole can reduce blood pressure going into capillaries.
(2 Marks)

Answer 23

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

Question 24

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

Answer 24

1. Increases dissociation of oxygen.
2. For aerobic respiration at the tissue/ muscle/ cell.
   OR anaerobic respiration is delayed at the tissue/ muscle/ cell.
   OR less lactate at the tissue/ muscle / cell.

Question 25

EPO is a performance enhancing drug which increases the percentage of red blood cells in the blood. A heart attack is caused by a lack of glucose and oxygen to the cardiac muscles via the coronary arteries. The overuse of EPO can increase the risk of heart attack. Suggest why. (2 Marks)

Answer 25

1. EPO causes the blood to thicken. 2. The thickened blood could block the coronary arteries. OR the thickened blood could slow blood flow. OR the thickened blood could cause clots.

Question 26

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

Answer 26

1. Increases/ more dissociation/ unloading. OR decreases haemoglobin affinity for oxygen. 2. By decreasing the blood PH/ increasing acidity.

Question 27

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

Answer 27

1. Pressure in left atrium is higher than in the ventricle causing the valve to open. OR when pressure above valve is lower than below the valve it opens. 2. Pressure in left ventricle is higher than in the atrium causing it to shut. OR when pressure in below valve is higher than pressure above valve it closes.

Question 28

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

Answer 28

Coronary arteries.

Question 29

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

Answer 29

1. Binding one oxygen molecule changes the territory/ quaternary structure of haemoglobin. 2. This creates another binding site. OR uncovers another haem group to bind to.

Question 30

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

Answer 30

1. Contraction of ventricles causes high blood/ hydrostatic pressure. 2. This forces water out of the blood capillaries.

Question 31

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

Answer 31

Excess tissue fluid cannot be reabsorbed/ builds up.

Question 32

The mass flow hypothesis is used to explain the movement of substances through the phloem. Use your knowledge of the mass flow hypothesis to explain how pressure is generated through the phloem tube. (3 Marks)

Answer 32

1. Sucrose is actively transported into the phloem. 2. Lowering the water potential 3. Water moves into the phloem by osmosis from xylem.

Question 33

A student is using coloured water to investigate the movement of water in leaf stalks in celery. Explain why the coloured water would move up the stalk. (3 Marks)

Answer 33

1. Water evaporates/ is transpired from the stalk/ leaves. 2. Water potential gradient/ lower water potential creates tension/ pulls the water up. OR osmosis creates tension/ pulls the water up. 3. Hydrogen bonds/ cohesion/ adhesion maintains column .

Question 34

Suggest how some plants can survive without xylem tissue. (1 Mark)

Answer 34

Short diffusion pathways to cells. OR it has a surface permeable to water/ ions into the cell.

Question 35

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

Answer 35

1. Water is lost from leaves due to evaporation/ transpiration of water molecules. OR transpiration/ evaporation/ diffusion of water molecules through stomata/ from leaves. 2. Lowers water potential of mesophyll/ leaf cells. 3. Water is pulled up the xylem causing tension. 4. Water molecules cohere/ stick together by hydrogen bonds. 5. Forming continuous water column. 6. Adhesion of water molecules to walls of xylem.

Question 36

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

Answer 36

1. In source/ leaf sugars are 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 the root. 5. Sugars used/ converted in root for respiration for storage.

Question 37

Describe the pathway taken by an oxygen molecules from the atmosphere to the respiring tissue in an insect. (4 marks)

Answer 37

1) Via spiracle 2) Down trachea 3) To tracheoles 4) Diffuses into respiring tissue 5) Down concentration gradient

Question 38

Kwashiorkor is a from of malnutrition caused by a diet extemely low in protein. Suggest how a deficiency in protein may affect the movement of fluid in capillaries. Give reason for your answer. (2 marks)

Answer 38

1) more fluid retained at tissues/ less fluid returned to capillaries. 2) Because less protein in the blood.

Question 38

Describe two differences between the structure of the xylem and the phloem. (2 marks)

Answer 38

1) Xylem has pits, phloem does not. 2) Xylem has lignin and phloem does not. 3) Phloem contains sieve plates and xylem does not. 4) Phloem contains cytoplasm and xylem does not.

Question 39

Describe and explain two specialisations of the root hair cell that enable it to absorb water from the soil. (4 marks)

Answer 39

1) Many/ multiple mitochondria AND 2) Active transport of ions into the cell. 3) Hair-like extension AND 4) Increased surface area. 5) Permanent vacuole AND 6) To keep water potential low 7) Thin walls AND 8) Reduces diffusion distance for diffusion.

Question 40

Describe the tree stages of the cardiac cycle, with reference to all the valves and the cardiac muscles in the atria and ventricles. (6 marks)

Answer 40

1) Arial systole 2) Atria contracts and ventricles relax 3) Atrioventricular valve opens and semilunar valve closed. 4) Ventricular systole 5) Ventricles contract and atria relax 6) Atrioventricular valves closed and semilunar valves open. 7) Diastole 8) Ventricles and atria both relaxed. 9) Atrioventricular valves open and semilunar valves closed.