WJEC Level 3 Certificate in Food Science and Nutrition

Section 2: Nutrition (LO2) 5 56 (AC2.1, AC2.2) The structure of nutrients Introduction In Chapter 4 you learned that there are five groups of nutrients: protein, fat, carbohydrate, vitamins and minerals. These are divided into macronutrients (protein, fat [ lipids ] and carbohydrate) and micronutrients (vitamins and minerals). All nutrients are vital for body growth, development and functions, but macronutrients are needed in larger amounts than micronutrients. In this chapter you will learn about the chemical structure of the nutrients and how this influences the way they are digested and used by the body. Having a knowledge of the chemical structure and chemical terms used in nutrition will also help you to understand the chemical properties and working characteristics of different foods, and how the nutrients they contain function in different recipes and are affected by food preparation and cooking processes. Water is also included in this chapter. Although it is not classified as a nutrient, it is nevertheless an essential component of the diet and the body cannot live without it. The chemical structure of the macronutrients AC 2.1 Chemical composition of protein Protein is made of the following chemical elements: Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen (N) Phosphorus (P) Sulphur (S) These elements are arranged into chemical units called amino acids , which join together in long chains, or polymers , to form protein molecules. A polymer is the general name for a substance that is mainly made up of a large number of similar units bonded together. You will find it is also used for other nutrients. Amino acids are known as the ‘building blocks’ of protein molecules. All living things – plants and animals – contain proteins, which perform a wide range of functions. In humans, there are twenty amino acids that are important. You need to be familiar with their names. These twenty amino acids join together in thousands of different sequences to form a vast number of different proteins that are found in the body. Chemical structure of proteins All amino acids have the same general formula, which is written like this: Study Tip Use the prompt word ‘N-CHOPS’ to help you remember the chemical elements in protein C NH 2 H OH O R C C NH 2 H R C C NH 2 H OH O R C Lipids – substances that are insoluble in water, but soluble in solvents, e.g. alcohol and ether. Lipids are referred to as fats when used in cooking Macronutrients – protein, fat and carbohydrate, which are needed in larger amounts than micronutrients Micronutrients – vitamins and minerals, which are needed in smaller amounts than macronutrients Key terms