What is a function of glycogen?
- support
- storage
- transport
- insulation
Show answer and explanation
Answer: B. storage
Glycogen is a storage polysaccharide.
A Level Biology: Biological molecules, questions with answers
Practise 70 real questions on Biological molecules from 2021 to 2026. See the answer and explanation as soon as you answer.
70real questions
66multiple choice
11exam sessions
About Biological molecules in A Level Biology
Biological molecules is one of the 11 main topics in our A Level Biology (Cambridge (CAIE) 9700) question bank, and about 11% of its real questions come from it. Tayyari Karo has 70 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2; 66 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 43 medium, 19 hard, 8 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
Try 6 real questions
These are real past-paper questions. Think of your answer first, then open the explanation.
Many animals use triglycerides for long-term energy storage. Which statements are correct additional functions of triglycerides?
1 They provide buoyancy in some marine animals.
2 They are the main components of cell membranes.
3 They are used as thermal insulation.
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
- 2 and 3 only
Show answer and explanation
Answer: C. 1 and 3 only
Triglycerides provide buoyancy and thermal insulation (statements 1 and 3); phospholipids, not triglycerides, are the main membrane component, so statement 2 is wrong.
In some people a mutation can affect the beta chains in their haemoglobin molecules. As a result polar amino acids on the outer surfaces of the chains are replaced by non-polar amino acids. What will be the effect on haemoglobin?
- Haemoglobin will become less soluble.
- Haemoglobin will become more soluble.
- Hydrophobic interactions between amino acids will decrease.
- More hydrogen bonds will form in the molecule.
Show answer and explanation
Answer: A. Haemoglobin will become less soluble.
Non-polar amino acids on the outer surface reduce interaction with water, so haemoglobin becomes less soluble (as in sickle cell haemoglobin).
The test for non-reducing sugars requires a second Benedict's test to be carried out. Which set of steps is the correct method for carrying out the non-reducing sugar test BEFORE carrying out the second Benedict's test?
- Perform the Benedict's test (negative result); warm gently with dilute hydrochloric acid; neutralise with sodium hydrogencarbonate.
- Perform the Benedict's test (colour remains red); boil with dilute hydrochloric acid; neutralise with sodium hydrogencarbonate.
- Perform the Benedict's test (colour remains blue); boil with dilute hydrochloric acid; neutralise with sodium hydrogencarbonate.
- Perform the Benedict's test (negative result); neutralise with sodium hydrogencarbonate; warm gently with dilute hydrochloric acid.
Show answer and explanation
Answer: C. Perform the Benedict's test (colour remains blue); boil with dilute hydrochloric acid; neutralise with sodium hydrogencarbonate.
A first Benedict's test must give a negative (blue, i.e. no reducing sugar) result; the sample is then boiled with dilute HCl to hydrolyse any non-reducing sugar into reducing sugars, then neutralised with sodium hydrogencarbonate before the second Benedict's test.
Bread contains a mixture of polypeptides known as gluten. Two of the polypeptides found in gluten are glutenin and gliadin. Which statement describes the tertiary structure of a protein?
- Disulfide bonds form between glutenin and gliadin.
- A large proportion of the amino acids in gliadin are glutamine.
- α-helical sections are found in glutenin and gliadin.
- Amino acids with hydrophobic R groups are found on the inside of glutenin.
Show answer and explanation
Answer: D. Amino acids with hydrophobic R groups are found on the inside of glutenin.
Tertiary structure describes the further folding of a single polypeptide chain, stabilised partly by hydrophobic interactions that bury hydrophobic R groups on the inside of the folded protein; bonds between two separate polypeptides (glutenin and gliadin) would be quaternary-level interactions, and α-helices are secondary structure.
In a healthy human, the mean value for the number of haemoglobin molecules in one red blood cell is 260 million. How many α-globin chains does one red blood cell contain in a healthy human?
- 1.3 × 10^8
- 2.6 × 10^8
- 5.2 × 10^8
- 1.04 × 10^9
Show answer and explanation
Answer: C. 5.2 × 10^8
Each haemoglobin molecule has 2 α-globin chains, so 260 000 000 × 2 = 5.2 × 10^8 chains.
Sessions with Biological molecules questions
| Session | Paper 1 | Paper 2 |
|---|---|---|
| May/June 2026 | 5 | – |
| May/June 2025 | 9 | 1 |
| October/November 2025 | 6 | – |
| May/June 2024 | 5 | – |
| October/November 2024 | 5 | – |
| May/June 2023 | 5 | 1 |
| October/November 2023 | 5 | – |
| May/June 2022 | 7 | 1 |
| October/November 2022 | 6 | – |
| May/June 2021 | 7 | 1 |
| October/November 2021 | 6 | – |
Common questions
What does the Biological molecules topic cover on this page?
70 real A Level Biology (9700) questions on Biological molecules from 2021 to 2026, from Paper 1, Paper 2. Each one shows the year, session and paper it came from.
Do I get the answers and explanations?
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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