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

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

3. 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

4. 3 Types of Carbohydrate
Monosaccharides
Disaccharides
Polysaccharides

5. 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

6. 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

7. 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

8. 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

9. 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.

10. 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

11. 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

12. Glycerol

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

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

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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

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

24. 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.

25. 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