Carbohydrates, fats and proteins

Proteins are made of amino acids joined in long chains. Amino acids contain carbon, hydrogen, oxygen and nitrogen. Animal sources of protein are meat, fish, eggs and milk; plant sources are beans, lentils, nuts and soya. Proteins have many jobs: they build and repair muscles and cells, they make enzymes, which are catalysts in the body and in washing powders, and they make antibodies that help to fight germs. Gelatin is a protein too. Insulin is a protein, and medicines can be made with genetic engineering. Laboratory tests exist for the three groups of food: iodine turns dark blue with starch, Benedict’s solution changes colour on warming with glucose, Sudan IV colours fat red, and Biuret turns violet with protein. We only read about these tests. Never use a test on yourself to find out if you have a medical condition: see a doctor. Use protein supplements only if a doctor advises. Whether people eat only plants is a discussion with different views.