BREATHING / GAS EXCHANGE. NAME. Q.Gas exchange takes place in the lungs. The diagram shows an alveolus next to a blood capillary in a lung. The arrows show the movement of two gases, A and B. (a) (i) Draw a ring around the correct answer to complete the sentence. diffusion. Gases A and B move by osmosis. respiration. () Gas A moves from the blood to the air in the lungs. Gas A is then breathed out. Name Gas A. () (iii) Which cells in the blood carry Gas B? Draw a ring around the correct answer. Page
platelets red blood cells white blood cells () (b) The average number of alveoli in each human lung is 280 million. The average surface area of million alveoli is 0.25 m 2. Calculate the total surface area of a human lung. Answer... m 2 (2) (c) An athlete trains to run a marathon. The surface area of each of the athlete s lungs has increased to 80 m 2. Give one way in which this increase will help the athlete. () (Total 6 marks) Q2. The human lung has about 80 million alveoli. The diagram shows some alveoli in a human lung. (a) Give three features of the alveoli that allow large amounts of oxygen to enter the blood.... Page 2
2... 3... (3) (b) (i) Name the process by which oxygen passes from the air into the blood. () Breathing allows large amounts of oxygen to enter the blood. Explain how breathing does this. (2) (Total 6 marks) Q3. The diagram shows the human circulation system. Page 3
(a) (i) Give the letter of one blood vessel that is an artery. () Give the letter of one blood vessel that carries oxygenated blood. () (b) During exercise, the heart rate increases. Explain, as fully as you can, why this increase is necessary. Page 4
(4) (Total 6 marks) Q4. Oxygen is transported round the body by the blood. Blood leaving the human lung can carry about 250 milligrams of oxygen per litre. However, only 7 milligrams of oxygen will dissolve in one litre of water at body temperature. (a) Suggest an explanation for the difference. (2) (b) Blood leaving the skeletal muscles during exercise may contain only 30 milligrams of oxygen per litre. Explain what causes the difference in oxygen concentration between the blood leaving the lungs and the blood leaving the skeletal muscles. Page 5
(4) (Total 6 marks) Page 6
M.(a) (i) diffusion carbon dioxide accept CO 2 / CO2 do not accept CO 2 (iii) red blood cells (b) 70 if no / incorrect answer then 70 000 000 or 280 x 0.25 gains mark ignore doubling the answer 2 (c) allows more gas / oxygen / CO 2 (exchange) do not accept air [6] M2. (a) large surface / large area thin / short distance (from air to blood) / one cell thick / two cells thick good blood supply / many capillaries / capillary network / many blood vessels ignore moist surface Page 7
(b) (i) diffusion ignore gaseous exchange brings (more) oxygen / air into the lungs / alveoli keeps O 2 level high in alveoli or maintains concentration difference (between alveoli and blood) / keeps O 2 concentration in alveoli > O 2 concentration in blood gains 2 marks [6] M3. (a) (i) B or D A or B (b) any four from: more / faster must be implied at least once for full marks increased blood (flow) ignore reference to breathing (more) oxygen supplied or aerobic respiration allow less anaerobic (respiration) or and prevents oxygen debt (more) glucose / sugar / food supplied ignore feeding (higher rate of) respiration Page 8
(more) energy needed / released allow made (more) carbon dioxide removed (muscles) doing (more) work or muscles contracting remove heat / cooling remove lactic acid or less lactic acid formed 4 [6] M4. (a) blood has red (blood) cells / haemoglobin haemoglobin combines with / carries oxygen ignore mix NB Blood can form oxyhaemoglobin = 2 marks (b) blood gains oxygen / becomes oxygenated (in the lungs) idea of acquiring oxygen must be unambiguous blood loses oxygen to the muscles / cells because muscles are respiring (aerobically) to provide energy (for exercise) [6] Page 9
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