Food Science and Nutrition
Core concepts
You must be able to classify nutrients (macronutrients: carbohydrate, protein, lipid; micronutrients: vitamins, minerals; plus water and fibre), state their functions, and link them to food sources. Know the chemistry of macronutrients: monosaccharides and disaccharides (glucose, fructose, sucrose, lactose), polysaccharides (starch, glycogen, cellulose), amino acids and peptide bonds, and the difference between saturated, monounsaturated, polyunsaturated and trans fatty acids. Digestion should be traced as mechanical plus chemical breakdown: salivary amylase in the mouth, gastric acid and pepsin in the stomach, bile emulsifying fats, pancreatic and brush-border enzymes in the small intestine, and absorption of monosaccharides and amino acids into the bloodstream via villi. Metabolism means anabolism versus catabolism and the role of ATP; energy balance is intake versus expenditure, with 17 kJ/g for carbohydrate and protein and 37 kJ/g for fat.
Traps
Questions often confuse functions with sources, or treat all fibre as digestible (it is not). Watch for 'essential' used loosely: essential amino acids and fatty acids cannot be synthesised in adequate amounts. Do not claim vitamins supply energy; they are coenzymes. Distinguish deficiency (scurvy, rickets, anaemia, iodine deficiency) from excess (saturated fat and cardiovascular risk, excess sodium and hypertension).
Worked rule of thumb
To estimate energy from a label: multiply grams of carbohydrate and protein by 17, fat by 37, then sum. A food with 20 g carbohydrate, 10 g protein and 5 g fat gives (20×17)+(10×17)+(5×37) = 340+170+185 = 695 kJ. Always show units and state that fibre and alcohol are excluded unless asked.