IGCSE Biology 0610: Nutrients in a Balanced Diet, Their Sources and Functions

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]

Part (a): Identifying nutrients and their functions

(i) Chicken filling. Protein

Chicken is rich in protein. Protein is needed by the body mainly for the growth and repair of body tissues.

(ii) Margarine. Fat

Margarine is a fat. Fat provides the body with a concentrated store of energy (more energy per gram than carbohydrate or protein) and also provides insulation, helping to reduce heat loss from the body.

(iii) Wholemeal flour. Carbohydrate and fibre

Wholemeal (whole grain) flour supplies carbohydrate, mainly as starch, which is the body’s main source of energy. It also supplies fibre, since whole grain flour retains the outer, indigestible parts of the grain. Fibre adds bulk to the food passing through the gut and helps it move along the alimentary canal, preventing constipation.

Part (b): The function of water

Water acts as a solvent in which many of the body’s chemical reactions take place, and it forms the main part of blood plasma, acting as a transport medium that carries dissolved substances, such as digested nutrients, around the body.

Part (c): The orange and scurvy

Oranges are a good dietary source of vitamin C. Eating an orange regularly, as part of a balanced diet, supplies Amara’s body with enough vitamin C to keep her gums, skin and other connective tissue healthy. Without a regular dietary source of vitamin C, over time, a person develops the deficiency disease scurvy, so including the orange in this lunch helps protect Amara from developing it.

Final answers

(a)(i) Protein; growth and repair of body tissues.
(a)(ii) Fat; a concentrated store of energy, and insulation.
(a)(iii) Carbohydrate (starch), providing energy; and fibre, adding bulk and preventing constipation.
(b) Water is a solvent for reactions and a transport medium (in blood plasma) for dissolved substances.
(c) Oranges supply vitamin C, which keeps gums and skin healthy and prevents scurvy.