1. Chapter 3Food

2. Why do we need Food? 1.Source of Energy 2.To make chemicals needed for metabolic reactions 3.As the raw materials for growth and repair of structures in an organism. Elements Present in Food Mainly made up of 14 elements The six common elements found in food are: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P) and Sulphur (S) Compounds containing Carbon are known as organic compounds.

3. There are 5 elements present as dissolved salts are: Sodium (Na), Magnesium (Mg), Chloride (Cl), Potassium (K) and Calcium (Ca). There are 3 trace (tiny quantities) elements: Iron (Fe), Copper (Cu), Zinc (Zn). Biomolecules contain carbon and are also called biochemicals. There are 4 main groups of biomolecules: Carbohydrates Lipids (fats, oils) Proteins Vitamins

4. Carbohydrates Elements in Carbohydrates: Carbon (C), Hydrogen (H), Oxygen (O) Elements are usually present in the ratio: Where X and Y are the same number (i.e. X = Y) Formula for Glucose:

5. Glucose is made by plants in photosynthesis and it is the main molecule used by living things for energy. Fructose: Same formula as glucose buy atoms arranged in a different way. Found in fruits and sweeter than glucose.

10. 4. Vitamins Vitamins are complex carbon based substances that the body cannot make. Two types: a)Water Soluble Vitamins

11. b.

12. Minerals

13. Water Water is essential for life for 3 main reasons: Importance of water for living things 1.It is a component of cytoplasm and body fluids 2.Water is an excellent solvent 3.Water participates in chemical reactions e.g. digestion 4.Water can easily pass in/out of cell membranes 5.Water is a good absorber of heat

14. Energy Transfer Reactions Examples 1.Formation of muscle from amino acids

15. Examples of catabolic reactions: 1.Respiration 2.Decay of plants