Human digestive system
Food is broken down so soluble molecules can be absorbed. Enzymes are biological catalysts: amylase digests starch, proteases digest proteins and lipases digest lipids. Bile emulsifies fats and provides alkaline conditions in the small intestine.
The heart is a double pump. Deoxygenated blood goes to the lungs; oxygenated blood goes to the body. Arteries have thick walls, veins have valves, and capillaries are thin for exchange.
Health and non-communicable disease
Coronary heart disease involves fatty deposits in coronary arteries. Risk factors include diet, smoking, lack of exercise and alcohol. Cancer is uncontrolled cell division. Benign tumours stay in one place; malignant tumours can invade and spread.
Plant organisation
Xylem transports water and minerals in one direction. Phloem translocates sugars. Root hair cells have a large surface area for water uptake. Stomata control gas exchange and water loss.
Taught with support from Joseph Danso, Science Lecturer in London. Book a session.