They are also known as the simple sugars

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Carbohydrates are composed of carbon, hydrogen and fifa 15 coins oxygen, of which the simplest form are monosaccharides such as glucose, fructose and galactose. They are also known as the simple sugars. Disaccharides are made up from two monosaccharide molecules, e.g. sucrose (table sugar) is made from glucose and fructose, maltose is made from glucose and glucose. The complex carbohydrates are polysaccharides of which starch is the plant storage form and glycogen the animal storage form. All the carbohydrates contain approximately the same amount of energy, i.e. 16 kJ/g. provides examples of the types of food high in carbohydrates which are either complex carbohydrates or simple sugars, whilst Table 6.3 illustrates the carbohydrate foods based on their glycaemic index. The latter is an index of the ability of the food to raise blood glucose levels; a high glycaemic index is indicative of a food being digested rapidly and absorbed as glucose, and thus elevating blood glucose. It should be noted that simple sugars such as fructose do not have a high glycaemic index because they do not elevate blood glucose.

Fats are composed essentially of carbon, hydrogen and oxygen. Fat is stored in the form of triglycerides, which consist of a glycerol and three fatty acid molecules. They may be found in adipose tissue, between muscles, and within muscle cells. During exercise triglycerides in adipose tissue are broken down to glycerol and fatty acids, which are then transported to the muscles for oxidation in the mitochondria. Fatty acids have been classified as being saturated or unsaturated depending on whether the bonds between the carbon atoms are saturated or not. Saturated fatty acids are generally of animal origin and are solid at room temperature whereas unsaturated fatty acids are mainly from plant origin and are liquid at room temperature. From a health perspective it is advisable to consume fats which are unsaturated rather than fats which are saturated (suggestions are that 60% of fat intake should be in the form of unsaturated fatty acids).

Proteins are made up of 20 or so naturally occurring amino acids. These molecules consist of carbon, hydrogen, oxygen and nitrogen. It is the nitrogen that has to be broken and eliminated as urea if taken in excess. Proteins are essential in the body not only as structural components but also because all enzymes are proteins; many of the hormones that integrate metabolism are proteins, and so are large macromolecules such as haemoglobin. The human body has a minimum requirement of protein in quantity and also in quality. The requirement with regard to quality is concerned with the fact that out of the 20 amino acids which make up all the proteins in our body, eight of them are essential. The eight essential amino acids are needed in small amounts regularly since we are incapable of making them ourselves, and a deficiency will ultimately lead to death. Essential amino acids can be found in meat, fish and some dairy products, as well as in plant products such as cereals, pulses and nuts.