Nutrition in Animals

20 Grade 10 Biology questions on Nutrition in Animals, with worked marking schemes. 20 questions are available on this topic in full.

1. Question 1

   6 marks

   Describe what happens to napier grass in the gut of a cow from the time it is swallowed until the products are absorbed.

   (6 marks)

   Marking scheme

   Award 1 mark each, maximum 6: - The grass is swallowed after very little chewing and passes down the oesophagus into the rumen, where it is softened and mixed. - Micro-organisms (bacteria and protoctists) living in the rumen secrete the enzyme cellulase. - Cellulase digests cellulose into glucose, which the micro-organisms ferment to fatty acids that the cow absorbs and uses for energy. - The coarse material is returned to the mouth as cud and chewed thoroughly by the ridged premolars and molars, using a side-to-side movement of the lower jaw, then swallowed again. - The re-swallowed cud passes through the reticulum and omasum, where water and some nutrients are absorbed. - In the abomasum (true stomach) hydrochloric acid and pepsin digest protein, including the protein of the micro-organisms carried along from the rumen. - Digestion is completed in the small intestine, and the amino acids, sugars and fatty acids are absorbed through the villi into the blood.

2. Question 2

   1 mark

   A learner argued that swallowed food travels down the oesophagus because of gravity. The teacher asked her to swallow a sip of water while lying flat on her back, and the water still reached her stomach. The correct explanation is that

   A. the stomach creates a suction that pulls the food down the tube.

   B. the diaphragm presses the food downwards each time it contracts.

   C. the oesophagus is a smooth, slippery tube down which food simply slides.

   D. circular muscles contract behind the bolus and relax in front of it, squeezing it along.

   (1 mark)

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3. Question 3

   1 mark

   A learner crushed a piece of ripe mango, added Benedict's solution and heated the mixture in a water bath. An orange-red precipitate formed. Which conclusion is correct?

   A. The mango contains starch.

   B. The mango contains a reducing sugar such as glucose or fructose.

   C. The mango contains only sucrose, which is a non-reducing sugar.

   D. The mango contains protein.

   (1 mark)

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4. Question 4

   1 mark

   Apart from killing most micro-organisms taken in with food, hydrochloric acid in gastric juice is important because it

   A. emulsifies fats before they pass on into the duodenum.

   B. provides the acidic pH at which pepsin works best and activates pepsinogen into pepsin.

   C. neutralises the alkaline pancreatic juice as it flows into the stomach.

   D. breaks down proteins directly into amino acids.

   (1 mark)

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5. Question 5

   1 mark

   A dog stripping meat from a bone places it at the side of its mouth and shears with the last upper premolar working against the first lower molar. These specialised teeth are

   A. canines, used for holding and killing prey.

   B. molars with broad ridged surfaces, used for grinding plant material.

   C. incisors, used for cutting flesh from the bone.

   D. carnassial teeth, used for shearing flesh and cracking bone.

   (1 mark)

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6. Question 6

   1 mark

   After a meal of chapati fried in oil, the fatty acids and glycerol absorbed by the villi of the ileum follow which route?

   A. Into the blood capillaries, where they are first converted to glucose.

   B. Into the lacteal, then through the lymphatic system before joining the blood.

   C. Into the blood capillaries and straight to the liver through the hepatic portal vein.

   D. Into the stomach lining, where they are stored as body fat.

   (1 mark)

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7. Question 7

   4 marks

   Learners at a school who eat sweets and drink sugary sodas during break, and who rarely brush their teeth, develop painful holes in their teeth. Explain how this happens.

   (4 marks)

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8. Question 8

   5 marks

   Describe what happens to the protein in a meal of githeri from the time it enters the stomach until it is absorbed.

   (5 marks)

   Marking scheme

   Award 1 mark each, maximum 5: - In the stomach, hydrochloric acid provides an acidic pH (about 2) suitable for gastric enzymes. - Pepsin hydrolyses the proteins into shorter chains called peptides (polypeptides). - The partly digested food passes into the duodenum, where bile and pancreatic juice make the medium alkaline. - Trypsin from the pancreatic juice acts on the remaining proteins and peptides, breaking them into smaller peptides. - In the ileum, peptidases from the intestinal juice hydrolyse the peptides into amino acids. - The amino acids are absorbed through the villi into the blood capillaries and carried in the hepatic portal vein to the liver.

9. Question 9

   1 mark

   A Grade 10 class examined the skull of a cow at an abattoir. They found no incisors on the upper jaw but a tough pad of tissue in their place, and a wide gap between the front teeth and the cheek teeth. Which statement best explains this arrangement?

   A. The missing upper incisors show that the cow swallows grass whole without cutting it.

   B. The cow wore away its upper incisors by grinding grass throughout its life.

   C. The gap is where the canine teeth will grow once the animal is fully mature.

   D. The lower incisors cut grass against the horny pad, while the gap allows the tongue to move the cut grass back to the grinding cheek teeth.

   (1 mark)

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10. Question 10

    3 marks

    Explain why food taken in by an animal must be digested before it can be used by the body cells.

    (3 marks)

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11. Question 11

    3 marks

    Account for the fact that a person whose diet contains very little roughage often suffers from constipation.

    (3 marks)

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12. Question 12

    2 marks

    State two factors that determine the amount of energy a person needs in a day.

    (2 marks)

    Marking scheme

    Award 1 mark each, maximum 2: - Age: growing children and adolescents need more energy for their body mass, while the need falls in old age. - Sex: males generally need more energy than females of the same age and body size. - Occupation or level of physical activity: a person doing heavy manual work needs more energy than one sitting in an office. - Body size or mass: a larger body needs more energy. - Special states of the body: pregnancy, breastfeeding and recovery from illness raise the energy need. - (Accept) Climate: more energy is needed to keep warm in cold conditions.

13. Question 13

    1 mark

    During a practical, a learner squeezed fluid from the gall bladder of a goat into a test tube containing cooking oil and water. After shaking, the oil formed very many tiny droplets that stayed suspended instead of settling as one layer. What does this demonstrate about the role of bile in digestion?

    A. Bile breaks the oil into tiny droplets, increasing the surface area on which lipase can act.

    B. Bile carries the oil into the lacteals of the villi.

    C. Bile supplies the acidic conditions that lipase needs in order to work.

    D. Bile digests the oil into fatty acids and glycerol.

    (1 mark)

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14. Question 14

    1 mark

    After a meal of githeri, more amino acids are absorbed than the body needs for growth and repair. The excess amino acids are carried in the hepatic portal vein to the liver. What happens to them there?

    A. They pass through the liver unchanged and leave the body as amino acids in the urine.

    B. They are stored in the liver as extra protein until the body needs them.

    C. The nitrogen-containing part is removed and converted to urea, while the remainder is used to release energy or is stored as glycogen.

    D. They are joined together to form starch, which is stored in the liver.

    (1 mark)

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15. Question 15

    3 marks

    Describe how you would test a sample of porridge for the presence of starch, and state the result you would expect if starch is present.

    (3 marks)

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16. Question 16

    4 marks

    State the role of each of the following nutrients in the human body: (i) iron; (ii) calcium; (iii) vitamin C; (iv) vitamin A.

    (4 marks)

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17. Question 17

    1 mark

    A two-year-old child is fed almost entirely on ugali and sukuma wiki, with hardly any milk, beans, eggs or fish. The child becomes swollen in the feet and abdomen and has thin, discoloured hair. The most likely cause of this condition is

    A. a diet lacking enough protein.

    B. too much starch, which the body stores as water in the tissues.

    C. a diet lacking enough carbohydrate, leaving the child with no energy.

    D. a lack of vitamin C, which causes bleeding under the skin.

    (1 mark)

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18. Question 18

    4 marks

    A patient has a pancreatic duct blocked by a stone. Explain why such a patient passes stools containing a lot of undigested fat.

    (4 marks)

    Marking scheme

    Award 1 mark each, maximum 4: - Pancreatic juice cannot flow from the pancreas into the duodenum. - The juice contains the enzyme lipase, which normally digests fats. - Fats are therefore not hydrolysed into fatty acids and glycerol. - Undigested fat molecules are too large and insoluble to be absorbed through the wall of the ileum. - The unabsorbed fat is therefore passed out in the faeces. - (Accept) The alkaline hydrogencarbonate in pancreatic juice is also missing, so the duodenal contents stay acidic and the little lipase present works poorly.

19. Question 19

    3 marks

    State three structural features of the ileum that adapt it for the absorption of digested food.

    (3 marks)

    Marking scheme

    Award 1 mark each, maximum 3: - It is long and its inner wall is folded and covered with numerous villi (and microvilli), giving a very large surface area for absorption. - The epithelium lining each villus is only one cell thick, giving a short distance for diffusion of digested food into the blood. - Each villus contains a dense network of blood capillaries that carry absorbed food away quickly, maintaining a steep concentration gradient. - (Accept) Each villus contains a lacteal for the absorption of the products of fat digestion / villi contain muscle fibres that keep them moving in the digested food.

20. Question 20

    1 mark

    Ugali eaten at lunch is chewed, mixed with saliva and swallowed. Starch digestion stops a short while after the food arrives in the stomach. Which statement explains why?

    A. The stomach secretes no juices, so no chemical digestion can occur there.

    B. All the starch has already been broken down to glucose in the mouth.

    C. Pepsin takes over and digests the starch more slowly than amylase does.

    D. Hydrochloric acid in the gastric juice denatures the salivary amylase.

    (1 mark)

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