Human Nutrition and Digestion: Biology 0610 (Cambridge O Level / IGCSE)

A school dietician is reviewing the lunch menu for a boarding school. The new menu removes the daily serving of milk, cheese and yoghurt from every meal, and replaces it with extra portions of rice and beans. No other change is made to the students' diet.

Which statement about the effect of this menu change is correct?

Farida eats a bowl of lentil and vegetable stew for dinner. Below are five events that happen to the stew inside her body, listed in a random order.

Event 1: Undigested plant fibre from the vegetables in the stew leaves Farida's body as part of her faeces.

Event 2: Farida places a spoonful of stew into her mouth and begins to chew it.

Event 3: Starch in the stew is broken down into smaller, soluble sugar molecules.

Event 4: The soluble sugar molecules produced in Event 3 pass through the lining of the gut wall into Farida's bloodstream.

Event 5: Once in the blood, some of the glucose is taken up by Farida's liver cells, which convert it into a stored carbohydrate called glycogen.

(a) For each of Events 1 to 5, name the biological process it describes. Choose each answer from: absorption, assimilation, digestion, egestion, ingestion. [5]

(b) State the region of the alimentary canal in which Event 4 mainly takes place. [1]

(c) Name one organ, other than a part of the alimentary canal itself, that releases a substance into the gut to help digest the stew, and state the substance that it releases. [2]

A stew contains rice (rich in starch), diced chicken (rich in protein) and a spoonful of groundnut (peanut) oil (a fat). After the stew is swallowed, it is digested as it passes along the alimentary canal.

(a) For each of the following nutrients in the stew, name the type of enzyme that digests it and state the small, soluble product(s) that are formed.

(i) starch in the rice [1]

(ii) protein in the chicken [1]

(iii) fat in the groundnut oil [1]

(b) Explain how bile helps in the digestion of the fat in this stew, and explain why bile itself is not classified as a digestive enzyme. [3]

(c) The partly digested food (chyme) leaving the stomach is strongly acidic, but the enzymes acting on the stew in the small intestine work best in alkaline conditions. Explain how the alkaline mixture released into the small intestine solves this problem, and suggest one reason why a strongly acidic stomach is still useful earlier in digestion. [3]

A rare intestinal condition damages the lining of a patient's small intestine, causing the villi there to become flattened and far less folded than normal, although the overall length of the small intestine does not change.

Which statement best describes the most direct effect of this condition on the patient?

A dentist is explaining to a young patient how different teeth are suited to eating different foods. She describes four teeth found in the patient's mouth without naming them.

Tooth W has a broad, flat biting surface with four rounded bumps, and is one of the two largest teeth found right at the back of the jaw.

Tooth X has a single sharp point and is used for gripping and tearing tougher food, such as meat.

Tooth Y has a thin, flat, chisel-shaped edge and is found at the very front of the jaw, used for cutting food into smaller pieces.

Tooth Z has two rounded bumps on its biting surface and sits between the pointed tooth and the teeth at the very back of the jaw.

(a) Name each tooth, W, X, Y and Z. [4]

(b) Describe how the enamel, dentine and pulp of a tooth are arranged, and state one function of each. [3]

(c) The dentist also explains that the stomach continues to physically break down food after it has been swallowed. Describe how the stomach carries out physical digestion of food. [2]

A sailor spends four months on a long sea voyage, eating only dried meat, ship's biscuit and salted fish, with no fresh fruit or vegetables available. Toward the end of the voyage, he develops swollen, bleeding gums, and small wounds on his skin stop healing properly.

Which statement best explains these symptoms?

Amara packs a lunch made up of a sandwich (wholemeal bread, chicken and margarine), an orange, and a bottle of water.

(a) For each of the following parts of the lunch, name the main class of nutrient it supplies to Amara's body and state one function of that nutrient.

(i) the chicken filling in the sandwich [2]

(ii) the margarine spread on the bread [2]

(iii) the wholemeal (whole grain) flour used to make the bread, name two different classes of nutrient it supplies, and state one function of each [2]

(b) State one function of the water that Amara drinks with her lunch. [1]

(c) Explain how including the orange in this lunch helps to protect Amara from the deficiency disease scurvy. [2]

Karim eats a mouthful of rice. Below are three events that happen to this mouthful as it moves along his alimentary canal.

Event 1: Saliva, which contains an enzyme that begins digesting the starch in the rice, is mixed with the food as Karim chews it.

Event 2: The chewed food is pushed by a wave of muscular contraction down a narrow muscular tube in the neck and chest, before it reaches the stomach.

Event 3: After most digestion of the rice is complete, water is reabsorbed from the remaining undigested material, producing semi-solid faeces.

(a) Name the organ in which each event mainly takes place. [3]

(b) Name the process by which the food is pushed along the tube described in Event 2, and describe how the muscles in the wall of this tube bring about this movement. [2]

(c) Suggest one problem Karim would experience if the muscles surrounding this tube stopped contracting properly. [1]

(d) Explain why the reabsorption of water described in Event 3 is important, and suggest what would happen to Karim's faeces if this organ failed to reabsorb water normally. [2]

A patient has a disease that severely damages her pancreas, so that it can no longer release digestive enzymes. Her salivary glands, stomach and the wall of her small intestine all continue to function normally.

Which statement correctly describes the most direct effect of this disease on digestion in her small intestine?

The wall of the small intestine is folded into millions of tiny, finger-like villi, and the surface of each villus is further covered in even smaller microvilli.

(a) Name two structures found inside each villus that absorb the small, soluble products of digestion, and state which digested nutrients each structure mainly absorbs. [4]

(b) State one feature of the wall of a villus that allows absorbed substances to diffuse into these internal structures over a very short distance. [1]

(c) Explain how the microvilli on the surface of each villus further increase the rate of absorption. [2]

(d) Explain why having millions of villi, rather than just a small number of larger folds, further helps the small intestine absorb nutrients efficiently. [1]