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State the three most common elements of life

• Carbon
• Hydrogen
• Oxygen

State the other elements needed by living organisms

See below

State a function of these elements

• Nitrogen - Component of DNA
• Sulphur - Components of proteins and coenzymes
• Phosphorus - Constituents of nucleic acids, ATP, phospholipids, Bones, and teeth
• Iron - Constituent of many enzymes, electron carriers, haemoglobin and myoglobin
• Potassium - Needed for nerve and muscle action and in protein synthesis

Outline the difference between an atom and an ion

• An ion is a charged particle.

An atom is the smallest particle of an element that can exist either alone or in combination.

Define organic

Compounds containing carbon that are found in living organisms (except hydrogen carbonates, carbonates, and oxides of carbon).

Outline the significance of water in biology

1. Transparency
2. Cohesion
3. Surface tension
4. Solvent properties
5. Thermal properties
6. Polarity of water molecules

Discuss the significance of water to organisms

• Coolant
• Transport medium
• Habitat

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