AQA GCSE Combined Science Foundation (8464), Foundation tier · Biology › Bioenergetics › Photosynthesis
Practise Uses of glucose from photosynthesis. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
What a plant does with the glucose it makes in photosynthesis: respiration, storage as starch or as fats and oils, cellulose for cell walls, and amino acids for proteins. Mostly short recall and explain questions, often linked to cell structure, transport in plants or food tests.
Key facts
Glucose → respiration (transfers energy)
Glucose → starch (insoluble store)
Glucose → fats and oils (store, e.g. in seeds)
Glucose → cellulose (strengthens cell walls)
Glucose + nitrate ions → amino acids → proteins
Nitrate ions are absorbed from the soil by root hair cells
Dissolved sugars move from the leaves in the phloem (translocation)
Respiration: transfers energy for the plant's living processes. Every living plant cell respires, day and night.
Starch: glucose is converted into insoluble starch for storage, for example in potato tubers, roots, leaves and seeds.
Fats and oils: glucose is used to make fats or oils (lipids) for storage, for example in seeds such as sunflower seeds.
Cellulose: glucose is used to make cellulose, which strengthens the cell wall.
Amino acids: glucose is used to make amino acids, which are joined together to make proteins such as enzymes.
The five uses of the glucose made in photosynthesis.
Why plants store starch
Glucose is soluble; starch is insoluble.
When the plant needs energy, for example at night or when a seed starts to grow, starch is broken back down into glucose for respiration.
Test for starch: iodine solution turns from orange-brown to blue-black.
Making proteins needs nitrate ions
Amino acids contain nitrogen, but glucose does not.
Plants absorb nitrate ions from the soil through their root hair cells by active transport.
Glucose and nitrate ions are used to make amino acids, and amino acids are joined to make proteins.
Moving glucose around the plant
diagram
Glucose is made in the leaves but used or stored all over the plant.
Dissolved sugars are carried from the leaves to the rest of the plant in the phloem. This is called translocation.
In a storage organ such as a potato tuber, the sugars are converted into starch.
Sugars move from the leaves to a potato tuber, where they are stored as starch.
How to answer each type of question
Give uses of the glucose made in photosynthesis
1 to 3 marksGrade 3
Count how many uses are asked for and give exactly that many.
Make each use specific: 'to make cellulose for cell walls', not just 'for growth'.
Check you have not given a use the question has ruled out.
Example. A potato plant makes glucose in its leaves. Give three ways the plant uses this glucose, other than storing it as starch.
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Any three from: for respiration (1); to make cellulose for cell walls (1); to make amino acids / proteins (1); to make fats or oils for storage (1).
Explain how glucose ends up stored in another part of the plant
3 marksGrade 5
Start where the glucose is made: in the leaves, by photosynthesis.
Say how it moves: dissolved sugars are carried in the phloem.
Finish with what happens in the storage organ: it is converted into starch.
Example. Potato tubers grow underground and contain a lot of starch. Explain how the starch in a tuber is made from carbon dioxide taken in by the leaves.
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The leaves use carbon dioxide to make glucose by photosynthesis (1). Dissolved sugars are transported from the leaves to the tuber in the phloem (1). In the tuber the sugar is converted into starch for storage (1).
Don’t lose marks
Saying plants store glucose as glycogen. Glycogen is the storage carbohydrate in animals; plants store starch.
Saying cellulose is an energy store or part of the cell membrane. It strengthens the cell wall.
Saying plants get glucose or proteins from the soil. Only water and mineral ions, such as nitrate, come from the soil.
Forgetting that respiration is a use of glucose: plants respire the glucose they make.
Writing that starch is stored because it is 'small'. Starch is a large, insoluble molecule.
More tips
Memory tricks
Five uses: 'Really Smart Plants Can Feast': Respiration, Starch, Proteins (via amino acids), Cellulose, Fats and oils.
Cellulose → cell wall: both start with 'cell'.
See 'nitrate' in a question? Think nitrogen → amino acids → proteins → growth.
Starch is Stored and Stays put, because it is insoluble.
Exam technique
Give specific uses, each with a purpose: 'converted into starch for storage', 'used to make cellulose to strengthen cell walls'.
In starch storage questions, the key word examiners look for is 'insoluble', linked to osmosis.
For nitrate questions, give the full chain: nitrate ions + glucose → amino acids → proteins → growth.
Be ready to link this topic to others: phloem (transport), iodine test (food tests) and active transport (root hair cells).
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
List the five uses of glucoseRespiration, starch for storage, fats or oils for storage, cellulose for cell walls, and amino acids for proteins.
Grade 4
State what cellulose is used forCellulose strengthens the cell wall of plant cells.
Grade 4
Name where plants store starch and oilsStarch is stored in leaves, roots and tubers such as potatoes; many seeds store oils.
Grade 5
Describe how glucose reaches storage organsSugars made in the leaves are carried in solution in the phloem to where they are used or stored.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Name the substance made from glucose that strengthens plant cell walls.
Cellulose
Plants absorb nitrate ions from the soil. Name the substances that plants make from glucose and nitrate ions.
Amino acids (which are used to make proteins)
Sugar beet makes sucrose from glucose. Name one other substance that plants make from glucose and use as a store of energy.
Starch (or fats / oils)
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Plants use the glucose made in photosynthesis in several ways.
(a) Which two of these are uses of glucose in plants? Tick (✓) two boxes.[2]
To absorb light energy
To make cellulose for cell walls
To make mineral ions
To make oxygen
To make starch for storage
(b) Plants store glucose as starch. Give one reason why starch is better for storage than glucose.[1]
(c) Name the substance made from glucose that strengthens plant cell walls.[1]
(d) Plants use glucose to make amino acids. Which ions, absorbed from the soil, are also needed to make amino acids?[1]
Show the answer and mark scheme
(a)Answer: To make cellulose for cell walls; To make starch for storage
(b)
starch is insoluble (so it does not affect osmosis)
(c)Answer: Cellulose
cellulose
(d)Answer: Nitrate ions
nitrate ions
Question 2Medium7 marks
Plants convert some of the glucose they make into other substances.
(a) Explain why plants convert glucose into starch for storage.[2]
(b) Sunflower seeds store oil rather than starch. Suggest one advantage of this for the seed.[1]
(c) A plant grown in soil containing no nitrate ions can still make glucose, but it cannot make proteins. Explain why.[2]
(d) Plants also use glucose for respiration. Explain why plant cells need to respire.[2]
Show the answer and mark scheme
(a)
starch is insoluble
(so) it does not affect the movement of water into or out of cells by osmosis
starch molecules are large, so they cannot move out of the cell
(b)
oil stores more energy per gram, so the seed can be smaller / lighter
(c)
amino acids / proteins contain nitrogen (as well as carbon, hydrogen and oxygen)
the nitrogen comes from nitrate ions (glucose does not contain nitrogen)
(d)
to transfer energy
for living processes, e.g. building larger molecules / growth / active transport of mineral ions