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DSE pp-Digestive system(A)
Discovery in Biology (BCH1200)
City University of Hong Kong
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Bio 1999 Q. 2(b)
i) After removal of A, bile cannot be stored. When food enters the duodenum, there will be insufficient bile to emulsify fats. This results in a reduction in the surface area for lipase to work on.
ii) The removal of structure D results in a reduction of the digestion and absorption of food. Therefore, the energy intake from food may become less than the energy expenditure of the body. This will lead to the consumption of the food reserves/ fats stored in the body.
iii) (1) insulin (2) The glucose level becomes higher as blood glucose cannot be converted into glycogen in the liver cells.
H. Bio 2000 Q. 2 (a)
i) The wall of the small intestine is highly folded/ has numerous villi which increase the surface area for food absorption. OR The wall of the small intestine contains muscles which contract and relax, and help to bring the digested food into better contact with the villi, thus facilitating food absorption.
ii) (1) smooth muscle (2) muscle B biceps no striations with striations involuntary voluntary not fatigue easily fatigue easily
iii) (1) lacteal (2) Fatty acids and glycerol diffuse into the villus. In the epithelial cells, they recombine into fat which is then passed into C.
Bio 2001 Q. 1(c)
(i) (1) C (2) A, B, D
(iii) This type of tooth is used for grinding food into smaller pieces. Without this grinding action, the food entering the digestive tract has a very small surface area for the enzymes to work on. As a result, the digestion by enzymes would be slower and it takes a longer time for digestion.
Bio 2003 2(c)
(i) The pancreas is the major organ that produces lipase. Due to blockage of the pancreatic duct, pancreatic lipase cannot reach the duodenum. Thus fat in the food cannot be digested and is egested in the faeces.
(ii) Due to the blockage of the pancreatic duct, digestive enzymes accumulate/ become active in the pancreas. The protease accumulated digests the tissue of the pancreas/ the lipase accumulated digests the cell membrane of pancreatic tissue cells.
(iii) The damaged pancreas secretes less insulin. Thus excessive glucose in the blood cannot be converted to glycogen in the liver. Blood glucose level in these patients remains so
high that the kidneys cannot reabsorb all glucose from the glomerular filtrate. Thus glucose is found in the urine.
H. Bio 2004 1(c) (i) Region X This is because food in A has passed through the mouth cavity. Salivary amylase will digest some of the starch in the food, but there is no enzyme to digest fat and protein.
(ii) Bile produced in the liver cannot be stored after the removal of B. When food enters the duodenum, insufficient amount of bile is released for emulsifying fats in the food. Thus, the surface area for the action of lipase decreases and fat cannot be digested efficiently.
H. Bio 2004 4(c)
(i) Molar
(ii) Tooth X has cusps on its top surface for grinding and crushing food. Tooth Y has sharp edge/ is chisel-like for biting and cutting food.
(iii) (1) Calcium is the structural material of the enamel and dentine.
(2) Tooth decay is caused by acid produced by bacteria breaking down sugars on tooth surface. More calcium intake has no effect on the action of bacteria on food.
Bio 2004 1 (a)
(i) X is a finger-like projection of the intestinal wall.
This feature provides a large surface area for food absorption.
The epithelium of X is very thin/ one-cell thick. This shortens the diffusion distance of digested food molecules.
(ii) X hepatic portal vein liver hepatic vein vena cava heart
(iii) The peristaltic contraction of the muscle layer pushes food along the small intestine. This also helps to mix food with digestive enzymes.
Bio 2005 Q. 3
(a) alkaline substance/ substance that inhibits acid secretion
(b) It is because usually bacteria are killed by the acid secreted by the stomach wall.
(c) helicobacter pylori is the cause of ulcer
(d) Introduce helicobacter pylori into the stomach of healthy mammals. If the hypothesis is correct, these animals would develop gastric ulcer symptoms.
(e) The churning action of the stomach will break down food into smaller pieces. This helps to increase the surface of food for enzymes to work on. It also helps to mix the food with the digestive enzymes.
Bio 2006 Q. 2
fatty acids and glycerol.
2009 Q. 1
2012 HKDSE Practice paper Q.
11.
2012 HKDSE Q. 10
DSE pp-Digestive system(A)
Course: Discovery in Biology (BCH1200)
University: City University of Hong Kong
