Ch 9 Transport of substances in humans Think about (Ch 9, p.2) 1. Blood transports various substances and distributes heat around the body. It also plays a role in body defence. 2. Blood is a liquid tissue consisting of blood cells (red blood cells, white blood cells and blood platelets) suspending in the plasma. 3. Blood is circulated in our body through double circulation: the pulmonary circulation and the systemic circulation (to be discussed in Section 9.5). Quick practice (Ch 9, p.9) 1. B 2. C Cell Y is a white blood cell. White blood cells are produced in the bone marrow and the spleen, and then mature in lymph nodes. Quick practice (Ch 9, p.19) A 1 is an artery. It has a thick muscular wall and a small lumen. 2 is a vein. It has a thinner wall and a larger lumen. 3 is a capillary. Its wall is one-cell thick. 4 is also a vein because valves are present. Quick practice (Ch 9, p.27) 1. A 2. B 3. C Blood vessel 1 (superior vana cava) carries deoxygenated blood from upper parts of the body to the heart. Blood vessel 3 (pulmonary artery) carries deoxygenated blood from the heart to the lungs. Blood vessel 2 is the aorta. Coronary arteries supply oxygen and nutrients to the heart muscles. If coronary arteries are blocked, heart muscles will not receive oxygen and nutrients and die. 1
Quick practice (Ch 9, p.31) D Quick practice (Ch 9, p.34) D At the capillaries, useful materials (oxygen and glucose) in the blood diffuse across the capillary walls into the surrounding tissue fluid. These materials then diffuse from the tissue fluid into body cells. On the other hand, waste products (carbon dioxide) diffuse out of the body cells into the tissue fluid, and then across the capillary walls into the blood. Quick practice (Ch 9, p.38) B Valves are present in both veins and lymph vessels. White blood cells are present in both veins and lymph vessels. Fat is present in both veins and lymph vessels. Section exercise (Ch 9, p.42) 1. (a) diffusion (b) multicellular (c) transport system 2. (d) circulatory system (e) lymphatic system 3. (f) blood (g) blood vessels (h) heart 4. C 5. D 6. E 7. B 8. A 2
9. (a) Aorta (b) Arterioles (c) Capillaries (d) Venules (e) Venae cavae 10. (a) Thin, with less elastic fibres (b) One-cell thick (c) Small (d) Large (e) Absent (f) Absent (g) Oxygenated / high (h) Deoxygenated / low (i) (j) Rapid Slow (k) High (l) Low 11. (a) R (b) P (c) S (d) T (e) Q 12. (a) atria (b) ventricles (c) septum 13. (d) bicuspid valve (e) tricuspid valve (f) contract (g) heart tendons 14. (h) semilunar valves (i) relax 3
15. F 16. T 17. F 18. T 19. C 20. B The capillary walls are differentially permeable. Red blood cells and plasma proteins are too large to pass through the capillary walls. Revision exercise (Ch 9, p.44) 1. D 2. B 3. A 4. D 5. C Cell X is a red blood cell. Cell Y is a white blood cell (phagocyte). Phagocytes can change shape and squeeze through the capillary wall while red blood cells are too large to pass through the capillary wall. A is incorrect. Normally, red blood cells are the most numerous of all blood cells. B is incorrect. White blood cells do not transport carbon dioxide. Carbon dioxide is mainly carried as hydrogencarbonate ions in the plasma. C is incorrect. White blood cells are produced in the bone marrow and the spleen. B is incorrect. The high blood pressure of the artery is generated by the pumping action of the heart. The artery contains elastic fibres which allow the wall to stretch and recoil to keep the pressure for maintaining blood flow. C and D are incorrect. Arteries have a small lumen. Blood vessel X is a pulmonary artery. It carries deoxygenated blood from the heart to the lungs. The recoil of the elastic wall of the aorta can keep the pressure high to maintain a continuous blood flow. Semilunar valves are located at the base of the aorta. They close to prevent the backflow of blood into the ventricles when the ventricles relax. A and B are incorrect. Contraction of the muscle in the wall of the aorta helps regulate the amount of blood flow instead of assisting blood flow. D is incorrect. Bicuspid valves are located between the left atrium and the left ventricle. Their closing prevent only prevent the backflow of blood from the left ventricle to the left atrium. 4
6. A 7. C 8. B 9. A 10. D 11. C 12. B There is a continual fall in blood pressure as blood flows from arteries through the capillaries to the veins. The total cross-sectional area of capillaries is the largest. Thus, the velocity of blood flow is the lowest. R is the bicuspid valve because it has two flaps, while S is the tricuspid valve because it has three flaps. X is the pulmonary artery, and Y is the aorta which has a thicker wall. P and Q are semilunar valves. They open and allow blood to be pumped out of the heart when the ventricles contract. The blood pressure at the arterial end of capillary bed is higher than that of the fluid surrounding the body cells. Due to retention of plasma proteins and blood cells in the blood, the water potential of the fluid in the intercellular space is higher than that of the blood. Some fluid is reabsorbed into the blood capillary by osmosis. The lack of skeletal muscle contractions reduces the flow rate of lymph in the lymph vessels, leading to the accumulation of excess tissue fluid in the legs. When people stretch their legs, leg muscles contract and squeeze lymph vessels. This helps the lymph flow and return to the blood circulation. 13. HKDSEE Biology 2012 Paper 1 Section B Q1 14. (a) The elastic fibres allow the artery walls to stretch when blood is pumped out of the heart. (1) The recoil of the elastic fibres helps maintain the blood pressure for a continuous blood flow. (1) (b) The smooth muscle can contract and relax (1) to regulate the amount of blood flow to the organs. (1) (c) The valves can prevent the backflow of blood (1) when the veins are squeezed by the surrounding muscles / due to gravity. (1) (Total: 6 marks) 15. (a) Contraction of the heart (muscle)/ ventricles increases the blood pressure. (1) Relaxation of the heart (muscle)/ ventricles decreases the blood pressure. (1) 5
(b) (i) 12.5 0.5 = 12 kpa (1) (ii) The blood pressure drops as the distance from the heart increases. (1) The narrow lumen of the blood vessels (capillaries) results in a high resistance to blood flow. (1) (c) This prevents damage to the thin walls of the blood vessels (capillaries). (1) The rate of blood flow is reduced to allow more time for material exchange. (1) (Total: 7 marks) 16. (a) Blood passes through the heart twice in one complete circulation. (1) Blood is pumped out from the heart to the lungs, and returns to the heart in the pulmonary circulation. (1) Blood is then pumped to the rest of the body and returns to the heart in the systemic circulation. (1) (b) Double circulation ensures a more efficient supply of oxygenated blood to body tissues because oxygenated blood and deoxygenated blood are separated / not mixing. (1) The heart can increase the pressure of the blood after it has passed through the lungs, so that blood can flow more quickly to the body tissues. (1) (Total: 5 marks) 17. (a) Any set of the following: (2) Fluid P contains plasma proteins while fluid Q does not (1) as the molecules are too large to pass through the capillary wall. (1) Fluid Q contains less glucose / oxygen (1) as some is taken up by the body cells for respiration. (1) Fluid Q contains more carbon dioxide / urea (1) resulted from metabolism of the body cells. (1) (b) (i) osmosis (1) (ii) lymphatic system (1) (c) Any one of the following: (1) Diffusion of oxygen becomes faster as more surfaces of the red blood cells are in contact with the capillary walls. (1) There is a shorter distance to centre of red blood cell so oxygen can diffuse faster into the cells. (1) The red blood cells pass through the capillary slowly, allowing more time for the exchange of gases. (1) (Total: 5 marks) 6
18. (a) aorta (1) (b) The left ventricle needs to produce a greater pressure / produce a greater force (1) to pump blood to whole body (except lungs) / pumps blood further. (1) (c) A: bicuspid valve (1) B: semilunar valve (1) (d) X, because 52.1% survived without replacement compared to 12.1% for Y. (1) 10.9% required repair or replacement of artificial heart compared to 41.4% for Y. (1) 37% died compared to 46.6% for Y. (1) (Total: 8 marks) 19. (a) (i) Y (1) (ii) The wall of X is thick (1) so as to withstand the high blood pressure in the blood vessel. (1) (iii) The blood pressure in the vessel type Y is lower. (1) The larger lumen reduces the resistance to blood flow. (1) (b) The oxygen content of the blood in vessel A is higher than that of the blood in vessel E. (1) (c) The carbon dioxide content of the blood in vessel A is lower that of the blood in vessel E. (1) (d) The blood glucose level in vessel D is higher than that in vessel C. (1) 20. HKCEE Biology 2010 Paper 1 Q3 (Total: 10 marks) 21. (a) (i) blood capillary (1) (ii) Its wall is one-cell thick / the diameter of the lumen is slightly greater or similar to that of a red blood cell. (1) (b) To provide a large surface area (1) for the exchange of materials between the blood and the tissue cells (1) (c) The pressure of blood in P is higher than the pressure of the fluid surrounding the muscle cells. (1) This forces the plasma except the plasma proteins out of P. (1) 7
(d) A low concentration of protein in the blood reduces the water potential gradient between the blood in the capillaries and the tissue fluid. (1) Less water in the tissue fluid is drawn into the blood capillaries (1) by osmosis. (1) 22. HKCEE Biology 2008 Paper 1 Q9(b) (Total: 9 marks) 23. (a) Any two of the following: (2) Blood contains red blood cells while lymph does not contain red blood cells. (1) Blood contains plasma proteins while lymph contains less / no plasma proteins. (1) Blood contains blood platelets while lymph does not contain blood platelets. (1) (b) The digested products of the fatty food are absorbed into the lacteal in the form of fat / oil droplets. (1) As a result, there will be numerous fat / oil droplets in the lymph in vessel X. (1) (c) Contraction of skeletal muscles in the legs around the lymph vessels forces the lymph to flow upward. (1) The valves in the lymph vessels help prevent the backflow of the lymph. (1) (d) As the lymph vessels are block, tissue fluid in the legs cannot be transported away. (1) Meanwhile it is continuously formed in the legs (1) thus tissue fluid accumulates. (Total: 8 marks) 24. Blood consists of blood cells (red blood cells, white blood cells and blood platelets) floating in plasma. (1) Role of blood plasma (max. 3) It consists mainly of water and transports dissolved substances (1) e.g. glucose / amino acids / urea /carbon dioxide / hormones / mineral ions. (1) It also carries plasma proteins, such as antibodies for body defence / fibrinogen for blood clotting.(1) It distributes heat throughout the body. (1) 8
Role of red blood cells (max. 3) It contains haemoglobin. (1) Oxygen combines with haemoglobin to form oxyhaemoglobin, and is carried from the lungs to all parts of the body. (1) Carbon dioxide combines with haemoglobin to form carbaminohaemoglobin, and is carried from respiring cells to the lungs.(1) Role of white blood cells (max. 3) Phagocytes destroy pathogens by engulfing them. (1) Lymphocytes produce antibodies (1) that destroy pathogens / neutralise toxins produced by the pathogens. (1) Role of blood platelets (max. 2) Blood platelets help in forming blood clots at wounds. (1) This stops further bleeding / prevent entry of pathogens. (1) (Total: 12 marks) 25. Knowledge on carbon dioxide transport (max. 7) Carbon dioxide diffuses from the liver cell into the tissue fluid surrounding it. (1) It then passes through the capillary wall into the blood (1) of the hepatic vein. (1) It is then transported within the plasma of the blood (1) in the form of hydrogencarbonate ions. (1) As carbon dioxide reaches the heart from the (inferior) vena cava, (1) the blood is pumped to the lungs via the pulmonary arteries. (1) Carbon dioxide passes along the artery and finally reaches the capillaries surrounding the air sacs. (1) Carbon dioxide then diffuses along the concentration gradient into the the air sacs.(1) Communication (max. 3) (Total: 10 marks) 9
Article reading (Ch 9, p.51) 1. Blood is not being used up by organs, but is returned to the heart through blood vessels. (1) There are no pores in the septum of the heart. Blood will not pass from one side of the heart to the other side through pores in the septum. (1) 2. He could not explain the connection between arteries and veins. (1) 3. A theory is accepted by scientists only when it can give satisfactory explanations to all the observed phenomena. It must be supported with evidence. (1) An accepted theory may change and evolve over time when new evidence and new technology emerges. (1) Galen s idea of blood flow remained unchallenged for over 100 years. However, Harvey was sceptical towards the idea and did experiments to prove that it was wrong. (1) 10