Food Science Nutrition - Definitions © PDST Home Economics

Definitions Nutrition: study of foods and their effects on the body. Nutrients: Chemical components of food needed for growth & repair of cells, providing heat and energy and proper body functioning. Macronutrients: nutrients needed in large amounts (grams g) by the body e.g. protein, fat, carbohydrate. (grams g) by the body e.g. protein, fat, carbohydrate. Micronutrients: nutrients needed by the body in very small amounts (milligrams mg, micrograms μg) by the body e.g. vitamins and minerals.

Definitions Elements: simple substances that cannot be broken into anything simpler. Nutrients are made of molecules made up of these elements. Organic Nutrients: Nutrients that contain the element Carbon e.g. protein, lipid, carbohydrate and vitamins. Inorganic Nutrients: do not contain the element Carbon e.g. minerals elements like Iron and Calcium. Metabolism: the total of chemical reactions which occur in the body. There are two types of metabolic reactions: (a) Catabolic reactions where big molecules are broken down and energy is released (e.g. cellular respiration). (a) Catabolic reactions where big molecules are broken down and energy is released (e.g. cellular respiration). (b) Anabolic reactions where small molecules are built into bigger ones using up energy (e.g. Growth). (b) Anabolic reactions where small molecules are built into bigger ones using up energy (e.g. Growth).

Definitions Enzymes: Biological catalysts that control chemical reactions in living things e.g. salivary amylase. Substrate: Substance the enzyme works on e.g. starch is the substrate for salivary amylase. Product: end result of the reaction controlled by the enzyme e.g. maltose is the product of the action of salivary amylase on starch.

Definitions Malnutrition: an imbalance in the diet, it could be due to too much of a nutrient e.g. obesity, or too little of a nutrient e.g. anaemia. Undernutrition: result of starvation e.g. Kwashiorkor and Marasmus due to lack of protein in the diet