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InkFlaskCambridge IGCSE
Contains the answers

Answers · A balanced diet

A balanced diet — return questions key

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

1. NR1 · Return

Model answer. Iron is needed to make haemoglobin, which carries oxygen in red blood cells. Calcium is for bones and teeth.

A full answer includes

  • Iron.

Also accept

  • iron

Watch for

  • “Calcium is needed for blood.” — Calcium is mainly for bones and teeth. Haemoglobin needs iron.

2. NR2 · Return

Model answer. Oranges, blackcurrants and red peppers are rich in vitamin C. Rice, butter and cheese contain almost none.

A full answer includes

  • Oranges, blackcurrants and red peppers.

Also accept

  • oranges, blackcurrants, red peppers

Watch for

  • “Every food from a plant is rich in vitamin C.” — Rice comes from a plant but has almost no vitamin C. Look for fruit and vegetables.

3. NR3 · Return

Model answer. Fibre adds bulk to the food in the gut, so food keeps moving and constipation is prevented. Water is a solvent in which the reactions in cells happen; it carries dissolved substances in the blood plasma; it carries waste out in urine; and sweat cools the body as it evaporates. The water comes from drinks and from food: fruit, vegetables and soup are mostly water.

A full answer includes

  • Fibre: adds bulk so food keeps moving through the gut, preventing constipation.
  • Water, any two of: solvent for the reactions in cells; transport in the blood plasma; carrying waste out in urine; cooling by sweating.
  • Sources of water: drinks, and foods that contain a lot of water, such as fruit, vegetables and soup.

Also accept

  • fibre: bulk, food keeps moving, prevents constipation; water: two of solvent, transport, urine, cooling; source: drinks and watery foods

Watch for

  • “Fibre is useless because it is not absorbed.” — Fibre does its job inside the gut.

4. NR4 · Return

Model answer. Carbohydrates are the main source of energy in most diets, and fats and oils are a source of energy too: the body stores spare energy as fat. Proteins are used for growth and repair, because new cells are built partly from proteins. Protein is not the main fuel, fats and oils do give energy, and making bones and teeth hard is the job of calcium, not of carbohydrates.

A full answer includes

  • Carbohydrates are the main source of energy in most diets.
  • Fats and oils are a source of energy that the body can store.
  • Proteins are used for growth and repair of cells and tissues.

Also accept

  • carbohydrates: main energy source; fats and oils: energy, stored; proteins: growth and repair

Watch for

  • “Protein is the body's main fuel.” — The body can respire protein, but its main job is building and repairing cells. Most energy comes from carbohydrates and fats.
  • “Fats and oils are of no use to the body.” — Fats and oils are a source and store of energy; they also insulate the body and are part of every cell membrane.

5. BR1 · Return

Model answer. Scurvy is caused by too little vitamin C in the diet. Citrus fruit, rich in vitamin C, cures it.

A full answer includes

  • Too little vitamin C in the diet.

Also accept

  • too little vitamin C

Watch for

  • “Scurvy is caught from other sailors.” — It is caused by the diet.

6. BR2 · Return

Model answer. A balanced diet contains all the nutrients the body needs, in the right amounts.

A full answer includes

  • g1: nutrients.
  • g2: amounts (proportions).

Also accept

  • nutrients; amounts (or proportions)

Watch for

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

7. BR3 · Return

Model answer. Rickets is caused by too little vitamin D or too little calcium. It affects the bones of children: they become soft and weak, and the legs may bend.

A full answer includes

  • Too little vitamin D or calcium.
  • The bones (they become soft and weak and may bend).

Also accept

  • too little vitamin D or calcium; the bones

Watch for

  • “Rickets is caused by too little vitamin C.” — That is scurvy. Rickets is about vitamin D and calcium.

8. BR4 · Return

Model answer. (a) No. Every other nutrient lasts the winter, but a balanced diet contains all the nutrients in the right amounts, and iron would run out after 8 weeks. For the last 8 weeks the team would get too little iron, which the body needs to make haemoglobin, the substance in red blood cells that carries oxygen. (b) Add a food rich in iron, such as dried beans, lentils or dried apricots (or red meat). It fills the gap because it contains the missing nutrient.

A full answer includes

  • (a) Not balanced: a balanced diet contains all the nutrients in the right amounts, and iron runs out after 8 of the 16 weeks, so the team would get too little iron for the rest of the winter.
  • (b) A food rich in iron, e.g. dried beans, lentils, dried apricots or red meat: it contains the missing nutrient, which is needed to make haemoglobin.

Also accept

  • (a) not balanced: iron runs short after 8 of the 16 weeks; (b) beans, lentils, dried apricots or red meat, because they contain iron

Watch for

  • “The crate is nearly balanced, because only one nutrient is short.” — One missing nutrient is enough: a balanced diet has every nutrient in the right amount.
  • “Milk powder would fill the gap, because milk is good for the blood.” — Milk is rich in calcium, for bones and teeth, but contains very little iron.