Food and Nutrition Science: Nutrients, Functions, Sources, Digestion and Metabolism
What this domain tests
Food and Nutrition Science is the foundation domain. The exam tests whether you can classify nutrients, state their functions and food sources, trace digestion and absorption, and explain energy metabolism in simple terms. Expect short structured questions and applied calculations.
Core rules and concepts
- The six nutrient classes are carbohydrates, proteins, fats, vitamins, minerals and water. Dietary fibre is a carbohydrate that is not digested and helps prevent constipation.
- Energy values: carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g. Alcohol supplies 7 kcal/g but is not a nutrient.
- Carbohydrates are the main energy source; proteins build and repair tissues and form enzymes; fats supply concentrated energy and carry fat-soluble vitamins A, D, E and K.
- Digestion begins in the mouth: salivary amylase acts on starch. Protein digestion begins in the stomach with pepsin and acid. Fat digestion is mainly in the small intestine, assisted by bile emulsification and lipase.
- Absorption occurs through villi in the small intestine; the large intestine absorbs water and some minerals. Metabolism includes catabolism (breaking down) and anabolism (building up), with ATP as the energy currency.
Worked example
A 100 g serving of boiled rice supplies about 28 g carbohydrate, 2.5 g protein and 0.3 g fat. Energy = (28 × 4) + (2.5 × 4) + (0.3 × 9) = 112 + 10 + 2.7 = 124.7 kcal. Reasoning: multiply each macronutrient mass by its energy factor, then add. If the same meal includes 100 g cooked beans (about 20 g carbohydrate, 9 g protein, 0.5 g fat), beans add (20 × 4) + (9 × 4) + (0.5 × 9) = 120.5 kcal. The combined dish supplies about 245 kcal and complementary plant proteins.
Traps that cost marks
- Do not treat fibre as a mineral or as a source of significant energy.
- Vitamin C and B vitamins are heat- and water-sensitive; long boiling lowers them.
- Plant iron is non-haem iron and is absorbed better with vitamin C; tea can inhibit absorption.
- Deficiency names are examinable: vitamin A night blindness, iron anaemia, iodine goitre, vitamin D rickets.
- Protein quality depends on essential amino acids; cereal-legume combinations improve it.