What's covered
Key facts
Cellular respiration
Aerobic respiration: glucose + oxygen → carbon dioxide + water (+ energy released).
Photosynthesis
Chlorophyll is the green pigment in chloroplasts that absorbs light energy (mainly red and blue wavelengths) for photosynthesis.
Cellular respiration
Aerobic respiration takes place in the mitochondria of cells.
Photosynthesis
The iodine test detects starch in a leaf: iodine solution turns blue-black in the presence of starch, confirming that photosynthesis has occurred.
Cellular respiration
Aerobic respiration requires oxygen and releases far more energy per glucose molecule than anaerobic respiration.
Photosynthesis
Carbon dioxide concentration is a limiting factor — increasing CO₂ up to a point raises the photosynthesis rate.
Cellular respiration
In animals, anaerobic respiration: glucose → lactic acid (+ a small amount of energy).
Photosynthesis
Light intensity is a limiting factor for photosynthesis — doubling light intensity increases the rate of photosynthesis until another factor becomes limiting.
Cellular respiration
In yeast (and some plant cells), anaerobic respiration: glucose → ethanol + carbon dioxide (+ a small amount of energy). This is called fermentation.
Photosynthesis
Photosynthesis is an endothermic reaction: it takes in (absorbs) energy from light, storing it as chemical energy in glucose.
Sample questions
A taste of the 22 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What is respiration?
- •Breathing air in and out of the lungs
- •Making glucose from CO₂ in plants
- •Pumping blood around the body in vessels
- ✓Releasing energy from glucose in cells
What raw materials does photosynthesis need?
- •Carbon dioxide and oxygen
- ✓Carbon dioxide and water
- •Nitrogen and water
- •Oxygen and glucose
What does aerobic respiration need?
- •Glucose and CO₂
- ✓Glucose and oxygen
- •Oxygen only
- •Water and oxygen
What products does photosynthesis make?
- •Glucose and carbon dioxide
- ✓Glucose and oxygen
- •Starch and nitrogen
- •Water and carbon dioxide
What products does aerobic respiration make?
- ✓Carbon dioxide and water
- •Ethanol and CO₂
- •Glucose and oxygen
- •Lactic acid and energy
Which factor limits photosynthesis on a cloudy day?
- •Air temperature
- ✓Light intensity
- •Plant height
- •Soil quality
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