Uses of glucose from photosynthesis - AQA GCSE Biology Exam Questions

Practise 36 exam-style questions on Uses of glucose from photosynthesis for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.

36 questions
2–6 marks each
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20 questions, marked as you go

Sample questions with model answers

Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.

Question 1

3 marks

Explain how plants use glucose and nitrate ions to make proteins.

Model answer

glucose provides carbon and energy; nitrate ions supply nitrogen; amino acids synthesised then joined to form proteins

Explanation

Plants combine carbon from glucose and nitrogen from nitrate ions to synthesise amino acids; these amino acids are linked together to form proteins used for growth and enzymes.

Mark scheme

1 mark
glucose provides carbon skeletons / energy
1 mark
nitrate ions supply nitrogen for amino acids
1 mark
amino acids are assembled into proteins (by peptide bonds)
Accept 'used in protein synthesis'.

Question 2

3 marks

Explain why high temperatures above optimal can reduce the conversion of glucose to starch.

Model answer

high temperatures denature enzymes involved in starch synthesis, reducing their activity; increased respiration at high temperature uses more glucose, leaving less for starch

Explanation

Enzymes that convert glucose to starch work within an optimal temperature range; overheating reduces their function and more glucose may be respired, so starch synthesis drops.

Mark scheme

1 mark
high temperature can denature / reduce activity of enzymes for starch synthesis
1 mark
higher respiration rates use more glucose for energy at high temperature
1 mark
overall less glucose available and less enzyme activity so less starch made

Question 3

4 marks

Explain why leaves synthesise cellulose but do not store most of their glucose as starch.

Model answer

cellulose is needed for cell wall structure to support leaf tissues; storing glucose as starch in leaves may disrupt osmotic balance and limit photosynthetic function, so starch is often stored in roots/tubers instead

Explanation

Leaves prioritise structural cellulose to maintain shape and function; storing large amounts of soluble sugars as starch in leaves could affect cellular water relations and photosynthesis, so plants translocate sugar to specialised storage organs.

Mark scheme

1 mark
cellulose is synthesised for cell walls to provide structural support
1 mark
starch storage in leaves would affect water potential (osmotic balance) and could interfere with cell function
1 mark
leaves are primary sites of photosynthesis and transport sugars away to storage organs (roots/tubers/seeds)
1 mark
starch is stored in specialised organs not usually in high amounts in leaf mesophyll

Question 4

5 marks

Compare the roles of glucose and sucrose in plants. Include transport, storage and metabolic use in your answer.

Model answer

glucose is primary product of photosynthesis and used in respiration and as building block (cellulose, starch); sucrose is a disaccharide formed for transport in phloem because it is less reactive and easily loaded/unloaded; starch is main storage; both can be converted into each other as needed

Explanation

Glucose is the immediate photosynthetic product used for metabolism and biosynthesis. For efficient transport, plants convert glucose into sucrose which is translocated in the phloem; at sinks it is converted and used or stored as starch.

Mark scheme

1 mark
glucose is produced by photosynthesis and used in respiration / as carbon source
1 mark
glucose is used to make structural molecules (cellulose) and storage (starch)
1 mark
sucrose is formed from glucose for transport in the phloem
Accept 'disaccharide' or 'transport sugar'.
1 mark
sucrose is less reactive / good for transport and is actively loaded into phloem
1 mark
interconversion: sucrose can be converted back to glucose at sinks; glucose can be polymerised to starch

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