Three and four mark questions

You may be expected to write in more depth for three and four mark questions. They might ask you about a process such as photosynthesis or respiration or compare differences, for instance between these two processes.

Where it is appropriate (Sample question 1 is an exception) remember to try to answer in complete sentences. The number of lines given to write your answer will give you an indication of how much writing is expected.

These questions have been written by Bitesize consultants as suggestions to the types of questions that may appear in an exam paper.

Sample question 1 - Foundation


Complete the following table comparing aerobic and anaerobic respiration. [4 marks]

Presence of oxygenPresent _________
Oxidation of glucose _________ Incomplete
Oxidation of glucoseThe products of respiration still contain energy
Products of respirationCarbon dioxide and waterMammalian muscle: _________
Products of respirationYeast: _________
Amount of energy released _________ Small amount
Presence of oxygenPresentAbsent/in short supply
Oxidation of glucoseCompleteIncomplete
Oxidation of glucoseThe products of respiration still contain energy
Products of respirationCarbon dioxide and waterMammalian muscle: lactic acid
Products of respirationYeast: ethanol and carbon dioxide
Amount of energy released(Relatively) large amountSmall amount

One mark is awarded for completing each row of the table.

For the answer on the presence of oxygen in anaerobic respiration, you would be allowed a mark for saying 'absent' or 'in short supply'.

Sample question 2 - Foundation


In an experiment investigating the effect of light intensity on photosynthesis in a pondweed, explain how a student kept the carbon dioxide constant at the beginning of the experiment. [3 marks]

Marking points are made from:

  • the student placed the pondweed in sodium hydrogencarbonate solution/added sodium hydrogencarbonate to the water [1]
  • the sodium hydrogencarbonate is a source of carbon dioxide [1]
  • the sodium hydrogencarbonate solution was the same concentration for each light intensity investigated [1]
  • or it could be that the same mass of sodium hydrogencarbonate was added, or sufficient sodium hydrogencarbonate was added to ensure that it wasn't limiting [1]

Sample question 3 - Higher


In a wood where bluebells live around the base of the trees, suggest what factors limit the rate of the bluebells' photosynthesis in the spring, and then in midsummer.

Explain your answer. [4 marks]


  • light intensity is limiting, because of shorter day lengths.
  • an answer referring to the possibility of poorer/more variable weather would be accepted.
  • temperature is limiting, because average daytime temperature would be lower.


  • light intensity is limiting, because the tree canopy would reduce light reaching the bluebells.
  • carbon dioxide concentration is limiting, because of the photosynthesis of other woodland plants and trees lowering it.

Sample question 4 - Higher


The graph shows some data from Long et al (2004) on how elevated carbon dioxide concentration affects production of glucose and starch in a plant.

Graph showing how CO2 affects production of glucose and starch in plants

Describe and explain the effects of elevated carbon dioxide concentration on glucose and starch in the plant. [4 marks]

Marking points are made from:

  • plant shows increased percentages of glucose and starch per unit leaf area.
  • the increases are 30% for glucose and 83% for starch. When asked to discuss data or information, try to quantify your analysis with numbers and look as closely at the data as you can.
  • because of increased rates of photosynthesis.
  • starch is built up from the glucose produced by photosynthesis.
  • starch showed a wider range of percentage increase - as shown by the range bars. This range could be quantified.

Remember, you must both describe and explain in order to access all of the marks available.