Life Processes and Health
Life Processes and Health
This domain covers nutrition, transport, reproduction, disease and the body's defences. Questions often ask you to link structure to function, interpret a health scenario, or correct a common claim about diet, blood or infection.
Core rules and concepts
- Photosynthesis stores energy: carbon dioxide + water → glucose + oxygen, using light and chlorophyll. Respiration releases energy from glucose in all living cells, all the time. Plants respire day and night; they photosynthesise only in light.
- Digestion is mechanical and chemical. Amylase acts on starch in the mouth; protease acts on protein; lipase acts on fats. Enzymes are specific and work best at optimum temperature and pH; high temperature denatures them.
- Transport: the heart pumps blood; arteries carry blood away from the heart, veins return it, capillaries exchange materials. The pulmonary artery carries deoxygenated blood to the lungs - an artery is not always oxygenated. Plants transport water and minerals in xylem and sucrose in phloem; transpiration pulls water up.
- Reproduction: pollination precedes fertilisation in flowering plants; in humans, fertilisation occurs in the oviduct. Pathogens include bacteria, viruses, fungi and protozoa. Antibiotics act on bacteria, not viruses. Immunity can be natural or acquired, active or passive.
Worked example
A patient has a fever and a sore throat. A swab shows a bacterium. Explain why an antibiotic may help but a cold remedy will not cure the infection. Reasoning: the antibiotic targets bacterial structures such as cell walls or ribosomes; the cold remedy relieves symptoms but does not kill the pathogen. The antibiotic must be prescribed and the full course taken to reduce resistance. If the swab showed a virus, antibiotics would be useless and misuse would select resistant bacteria.
Traps that cost marks
Saying plants only respire at night; claiming digestion begins in the stomach (starch digestion begins in the mouth); calling the pulmonary artery oxygenated; saying antibiotics cure viral infections; confusing pollination with fertilisation; forgetting that enzymes are proteins and are denatured, not 'killed'.