The main functions of food are: Food for Life The main functions of food are: Energy Growth and repair of cells To control metabolism

Chemical components of food There are 5 main types of molecules found in food Water Proteins Lipids Carbohydrates Vitamins + minerals

Carbohydrates Carbohydrates contain the elements Carbon Hydrogen Oxygen In the ratio of 1C:2H:1O You have twice as many oxygen molecules as carbon or hydrogen

3 Types of Carbohydrate Monosaccharides Disaccharides Polysaccharides

These are single sugar molecules Monosaccharides These are single sugar molecules They are known as simple sugars They are soluble in water They are sweet to taste Examples: glucose, fructose Source: Fruit

Source: table sugar, milk Disaccharides These are two sugar units joined together They are known as double sugar molecules They are soluble in water They are sweet to taste Examples: sucrose, lactose Source: table sugar, milk

Polysaccharides These consist of many sugar molecules joined together They are not soluble in water They do not taste sweet Example: starch Source: bread, pasta, cereals

Functions of Carbohydrate Cell Structure Cellulose in plant cell walls Chitin in fungal cell walls Metabolism Respiration – glucose breaks down to form carbon dioxide and water - catabolism Photosynthesis – glucose molecules are forms from carbon dioxide and water using the suns energy –anabolism Carbohydrate is stored as starch in plants Carbohydrate is stored as glycogen in animals

Lipids Lipids are a diverse group of substances which include fats and oils steroids which include cholesterol and some of the sex hormones various other substances such as the waxes which cover insect bodies and plant leaves.

Structure of Lipids They are made up of the elements carbon hydrogen oxygen They do not have the same ratios as carbohydrates. They are made up of two main types of molecules Fatty acids Glycerol

Fatty Acids There are many different types of fatty acid They are all represented by the general equation R COOH R is a long hydrocarbon chain COOH is a carboxyl group

Glycerol

Types of Lipid Two of the main types of lipids are Triglycerides Phospholids

Triglyceride This is the smallest lipid It is made up of 3 fatty acid molecules and 1 glycerol molecule

Phospholipids If one fatty acid of a lipid molecules is replaced by a phosphate group the a phospholipid is formed

Function of Lipids Cell Structure Phospholipids are major components in cell membranes Heat insulation Protection around body organs Waterproof the body Myelin helps transmit messages in nerve cells Metabolism Lipids form the long term energy store of organisms

Proteins Proteins contain the elements Carbon Hydrogen Oxygen Nitrogen Some may also contain sulphur, iron and phosphorous Proteins are found in lean meat, fish pulses, soya and eggs

Structure of Proteins Proteins are made up of long chains of amino acids There are 20 different amino acids Amino acids are joined together by peptide bonds They join together to form polypeptide chains

Amino Acids a single hydrogen atom an amino group All amino acids contain four distinct chemical groups connected to a central carbon atom: a single hydrogen atom an amino group a carboxyl group a side chain

Functions of Proteins Cell structure Proteins combine with phospholipids to from cell membranes They form Keratin in hair skin and nails They form Myosin in muscle Haemoglobin is a protein Metabolism All enzymes are proteins. Enzymes control the chemical reactions in cells. Hormones regulate body functions Chlorophyll traps the sun’s energy during photosynthesis

Vitamins Vitamins are organic compounds We need Vitamins A,B, C, D, E and K in our diets to keep us healthy. Vitamins can be water soluble or fat soluble Vitamins B and C are water soluble Vitamins A D E and K are fat soluble

Sources of Vitamins Vitamin Source A Green leafy vegetables, Eggs, Cheese, Carrots B Lean Meat, Cereals, Nuts C Citrus Fruits, Green vegetables, Turnips D Milk and Milk products, Sunlight E Vegetable oils, fish, nuts K Green leafy vegetables

Functions of Vitamins Functions Fight Infection B Metabolism, Nerve function C Prevents gingivitis, skin and blood vessels D Builds healthy bones and teeth E Prevents heart disease K Helps blood clot

Minerals Minerals are required by organisms in very small amounts They are required to Form part of rigid body tissues Calcium in bones and cell walls Form certain pigments Iron is needed for Haemoglobin is the red pigment of blood Magnesium is needed for Chlorophyll the green pigment in plants Regulate body fluids Sodium balances water content in cells Minerals salts are present in rocks. When they dissolve in water they are absorbed by plants and animals. They do not provide any energy.

Water Cells are made up of 70% to 95% Water Water Keeps temperature steady sweat and transpiration Good solvent – transports chemicals Controls cell shape Participates in chemicals reactions photosynthesis and digestion