Organisation
What's covered
Key facts
The region of the enzyme where the substrate binds is called the active site.
Alveoli are adapted for efficient gas exchange by their large surface area, thin walls (one cell), and rich blood supply.
Artificial (mechanical) hearts avoid donor-rejection issues and waiting-list delays, but mechanical parts can fail and the patient typically needs anticoagulant medication. They are usually a temporary bridge to transplant.
Guard cells open and close the stomata to control gas exchange and water loss.
Arteries carry blood away from the heart at high pressure; veins carry blood back towards the heart at low pressure.
Amylase breaks down starch into simple sugars (maltose / glucose).
Amylase digests starch into maltose (a sugar).
The tiny air sacs in the lungs are called alveoli.
Coronary heart disease (CHD) is caused by fatty plaques (atheroma) building up inside the coronary arteries, narrowing them and restricting blood flow to the heart muscle.
Guard cells control the opening and closing of stomata.
Sample questions
A taste of the 99 questions in this topic — answers marked. Sign up to practise the full set with spaced repetition.
What is an enzyme?
- ✓A biological protein catalyst
- •A simple carbohydrate sugar
- •A type of fat-storage molecule
- •A waste product from digestion
What adaptation gives the alveoli a large surface area for gas exchange?
- •A coating of cilia that beat to circulate air
- •A single large hollow chamber inside the lung
- •A thick muscular wall around each lung lobe
- ✓Millions of tiny air sacs lining each lung
What causes coronary heart disease?
- •Excess water in the bloodstream
- ✓Fatty plaques in coronary arteries
- •Lack of red blood cells
- •Viral infection of the heart wall
What is transpiration?
- •Absorption of water by roots
- ✓Loss of water vapour from leaves
- •Movement of sugar through phloem
- •Photosynthesis in leaf cells
Which blood vessel carries oxygenated blood from the lungs to the heart?
- •Aorta
- •Pulmonary artery
- ✓Pulmonary vein
- •Vena cava
What is the role of bile?
- •Absorbs water from food residues
- •Breaks down protein to amino acids
- ✓Emulsifies fats and neutralises acid
- •Produces enzymes in the pancreas
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