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Chapter 3 Food
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.
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
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:
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.
4. Vitamins
Vitamins are complex carbon based substances that
the body cannot make.
Two types:
a) Water Soluble Vitamins
b.
Minerals
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
Energy Transfer Reactions
Examples
1.
Formation of muscle from
amino acids
Examples of catabolic reactions:
1.
Respiration
2.
Decay of plants