Organisation
What's covered
Key facts
Enzymes
The region of the enzyme where the substrate binds is called the active site.
Gas Exchange (Edexcel)
Alveoli are adapted for efficient gas exchange by their large surface area, thin walls (one cell), and rich blood supply.
Heart Disease
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.
Plant Organisation
Guard cells open and close the stomata to control gas exchange and water loss.
The Blood and Heart
Arteries carry blood away from the heart at high pressure; veins carry blood back towards the heart at low pressure.
The Human Digestive System
Amylase breaks down starch into simple sugars (maltose / glucose).
Enzymes
Amylase digests starch into maltose (a sugar).
Gas Exchange (Edexcel)
The tiny air sacs in the lungs are called alveoli.
Heart Disease
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.
Plant Organisation
Guard cells control the opening and closing of stomata.
Practice questions with answers
A taste of the 84 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 disease is caused by fatty deposits narrowing the arteries that supply the heart muscle?
- •cardiac arrhythmia
- ✓coronary heart disease
- •heart valve disease
- •myocardial infarction
What does xylem transport in plants?
- •Oxygen from leaves
- •Sugars only
- ✓Water and mineral ions
- •Water and sugar together
Which blood vessel carries oxygenated blood from the lungs to the heart?
- •Aorta
- •Pulmonary artery
- ✓Pulmonary vein
- •Vena cava
Where is bile stored?
- ✓Gall bladder
- •Liver tissue
- •Pancreas duct
- •Stomach wall
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