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Answers · A balanced diet

A balanced diet — final check key

Check meaning, not exact wording. These are teaching points, not official Cambridge marks.

1. NK1 · Final check

Model answer. (a) Carbohydrates are a source of energy; bread, rice, potatoes and pasta are rich in starch. (b) Fats and oils are a source and store of energy, insulate the body and are used to make cell membranes; butter, cooking oil and nuts are rich in fat. (c) Proteins are used for growth and repair of cells and tissues; meat, fish, eggs, beans and cheese are rich in protein.

A full answer includes

  • (a) Energy; for example bread, rice, potatoes or pasta.
  • (b) Energy (and a store of energy), insulation, cell membranes; for example butter, cooking oil or nuts.
  • (c) Growth and repair of cells and tissues; for example meat, fish, eggs, beans or cheese.

Also accept

  • (a) energy + a starchy source; (b) energy store, insulation or membranes + a fatty source; (c) growth and repair + a protein source

Watch for

  • “Protein is mainly for energy.” — Its main job is growth and repair.

2. NK2 · Final check

Model answer. (a) Vitamin C keeps the skin and gums healthy and helps wounds heal; oranges, blackcurrants, peppers and broccoli are good sources. (b) Vitamin D helps the body absorb calcium, for strong bones and teeth; oily fish, egg yolk and fortified foods contain it, and the skin makes it in sunlight. (c) Calcium makes bones and teeth hard; milk, cheese and yoghurt are good sources. (d) Iron is needed to make haemoglobin, which carries oxygen in red blood cells; red meat, beans, lentils and spinach contain iron.

A full answer includes

  • (a) Healthy skin and gums, wound healing; citrus fruit, blackcurrants, peppers, broccoli.
  • (b) Absorbing calcium for strong bones and teeth; oily fish, egg yolk, fortified foods (also made in the skin in sunlight).
  • (c) Hard, strong bones and teeth; milk, cheese, yoghurt, sardines eaten with their bones, fortified plant drinks.
  • (d) Making haemoglobin, which carries oxygen in red blood cells; red meat, beans, lentils, spinach.

Also accept

  • (a) skin, gums, healing + fruit or vegetable; (b) calcium absorption, bones + oily fish, egg, fortified food; (c) bones and teeth + dairy; (d) haemoglobin + meat, beans, leafy greens

Watch for

  • “Vitamin D makes bones hard by itself.” — Calcium hardens bones; vitamin D helps the body absorb it.

3. NK3 · Final check

Model answer. Fibre is not digested, but it adds bulk to the food in the gut, so the gut muscles can push food along and constipation is prevented. Water is needed as the solvent in which the reactions in cells happen, to carry substances in the blood plasma, to carry waste out in urine and to cool the body by sweating. Nutrients have other jobs besides releasing energy.

A full answer includes

  • Fibre adds bulk so the gut muscles can push food along; it prevents constipation.
  • Water is a solvent for the reactions in cells, carries substances in the blood plasma and waste in urine, and cools the body in sweat.

Also accept

  • fibre: bulk, keeps food moving, prevents constipation; water: solvent, transport, waste removal or cooling

Watch for

  • “Water is not a nutrient, because it gives no energy.” — The body needs water every day for jobs that have nothing to do with energy.

4. BK1 · Final check

Model answer. A balanced diet is one that contains all the nutrients the body needs, carbohydrates, fats and oils, proteins, vitamins, mineral ions, fibre and water, each in the right amount: not too little of any, and not far more than needed.

A full answer includes

  • It contains all the nutrients: carbohydrates, fats and oils, proteins, vitamins, mineral ions, fibre and water.
  • Each nutrient is in the right amount (not too little, and not far more than needed).

Also accept

  • all the nutrients; in the right amounts

Watch for

  • “A balanced diet has equal amounts of every nutrient.” — Each nutrient is needed in its own right amount.

5. BK2 · Final check

Model answer. (a) Scurvy is caused by too little vitamin C in the diet. (b) Rickets is caused by too little vitamin D or too little calcium.

A full answer includes

  • (a) Too little vitamin C in the diet.
  • (b) Too little vitamin D or calcium.

Also accept

  • (a) too little vitamin C; (b) too little vitamin D or calcium

Watch for

  • “Rickets is caused by too little vitamin C.” — That is scurvy.

6. BK3 · Final check

Model answer. (a) The store is not balanced. Vitamin D would last only 4 weeks and calcium 7 weeks, far less than the 16-week winter, and a balanced diet needs every nutrient in the right amount. (b) In children, too little vitamin D or calcium can cause rickets. (c) Add a food rich in both, such as sardines eaten with their soft bones or a fortified plant drink with vitamin D and calcium added.

A full answer includes

  • (a) Not balanced: vitamin D (4 weeks) and calcium (7 weeks) would run short; every nutrient must be in the right amount.
  • (b) Rickets.
  • (c) Sardines or other oily fish eaten with bones, or a fortified plant drink: it supplies vitamin D and calcium.

Also accept

  • (a) not balanced, vitamin D and calcium short; (b) rickets; (c) sardines or fortified drink, vitamin D and calcium

Watch for

  • “If most nutrients are enough, the diet is balanced.” — Every nutrient must be there in the right amount.