AQA GCSE Biology 8461: Cell structure – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover section 4.1.1 Cell structure (4.1.1.1 to 4.1.1.6) of the AQA GCSE Biology (8461) specification, for first teaching 2016 with exams from 2018 (version 1.0), including required practical activities 1 and 2. Cell biology is examined on Paper 1, set at Foundation and Higher Tier. The part that needs standard form for bacterial numbers is marked (Higher), because the specification makes giving that answer in standard form Higher tier only; all other questions and parts suit both tiers. A calculator is allowed.

Learn the content first with the Cell structure study guide and the Cell structure revision notes. These questions are different from the topic-level Cell biology practice questions, which also test division and transport. The course hub is AQA GCSE Biology and the printable checklist lists every topic.

Questions

1. Bacterial cells and animal cells share some features but differ in others.

(a) Name two structures found in both a bacterial cell and an animal cell. [2] (b) Give two ways the genetic material of a bacterial cell differs from that of an animal cell. [2]

2. Sub-cellular structures have specific functions.

(a) State the function of mitochondria. [1] (b) State the function of ribosomes. [1] (c) State the function of the cell membrane. [1] (d) Root hair cells are found underground. Suggest why they have no chloroplasts. [1]

3. Unit conversions.

(a) Convert 0.025 mm to micrometres. [1] (b) Convert 450 nm to micrometres. [1] (c) Write 25 μm in metres, in standard form. [1]

4. In an electron micrograph a chloroplast is 48 mm long. Its real length is 6 μm.

(a) Calculate the magnification of the micrograph. [3] (b) Explain why an electron microscope is used, rather than a light microscope, to study the inside of a chloroplast. [2]

5. A drawing of an animal cell has a scale bar 30 mm long, labelled 5 μm. The nucleus in the drawing is 42 mm across.

(a) Calculate the magnification of the drawing. [2] (b) Calculate the real diameter of the nucleus in micrometres. [2]

6. Cell X is 8 × 10⁻⁵ m long. Bacterium Y is 8 × 10⁻⁷ m long.

(a) How many times longer is cell X than bacterium Y? [1] (b) State how many orders of magnitude apart the two lengths are. [1] (c) Give the length of cell X in micrometres. [1]

7. Sperm cells and xylem cells are specialised.

(a) Explain how a sperm cell is adapted to its function. [3] (b) Describe one adaptation of xylem cells and explain how it helps the plant. [2]

8. Cells lining the small intestine have many tiny folds in their cell membrane. They contain many mitochondria. They absorb some substances by active transport, which needs energy.

Use this information to explain how these cells are adapted to their function. [4]

9. Cell differentiation.

(a) Describe what happens to a cell as it differentiates. [2] (b) Compare differentiation in animals and plants, and state what cell division is mainly used for in mature animals. [3]

10. A student wants to observe onion epidermis cells with a light microscope.

(a) Describe how she should prepare the slide, use the microscope and record what she sees. [6] (b) The eyepiece lens is ×10 and the objective lens is ×40. Calculate the total magnification. [1]

11. A student investigated the effect of two antiseptics, A and B, on the growth of bacteria. She placed a paper disc soaked in each antiseptic, and a control disc, on an agar plate covered with bacteria. After incubation, the clear zone around disc A had a diameter of 12 mm. The clear zone around disc B had a diameter of 22 mm. There was no clear zone around the control disc.

(a) Explain why the lid of the Petri dish was secured with tape and the dish was stored upside down. [2] (b) Explain why the plate was incubated at 25°C. [1] (c) Calculate the area of each clear zone. Give your answers to 3 significant figures. [3] (d) Calculate how many times larger the clear area for B is than for A. [1] (e) State what the control disc should have been soaked in, and why it is used. [1] (f) Give two variables the student should have kept the same. [2]

12. A bacterium has a mean division time of 20 minutes. A culture starts with 250 bacteria.

(a) (Higher) Calculate the number of bacteria after 4 hours. Give your answer in standard form. [3] (b) Suggest one reason the real number may be lower than your answer. [1]

Answers

1. (a) Cell membrane [1]; cytoplasm [1]. (b) Not enclosed in a nucleus [1]; it is a single DNA loop, and there may be plasmids (small rings of DNA) [1]. Examiner insight: “Bacteria have no DNA” scores nothing in (b); the mark needs the idea that the DNA is not in a nucleus.

2. (a) Site of aerobic respiration, releasing energy [1]. (b) Protein synthesis [1]. (c) Controls which substances enter and leave the cell [1]. (d) No light reaches them, so they cannot photosynthesise [1]. Examiner insight: “Mitochondria make energy” is usually not credited, because energy is released, not made; write “release energy”.

3. (a) 0.025 × 1000 = 25 μm [1]. (b) 450 ÷ 1000 = 0.45 μm [1]. (c) 2.5 × 10⁻⁵ m [1]. Examiner insight: In standard form the number in front must be between 1 and 10, so 25 × 10⁻⁶ m is not accepted where standard form is asked for.

4. (a) 48 mm = 48 000 μm [1]; magnification = 48 000 ÷ 6 [1] = ×8000 [1]. (b) The electron microscope has a much higher resolution (resolving power) [1], so small structures that are close together can be seen as separate, in fine detail [1]. Examiner insight: The unit-conversion step earns its own mark, and a final answer with no unit for magnification is correct; ×8 from unconverted values gets only the method mark.

5. (a) 30 mm = 30 000 μm, and 30 000 ÷ 5 [1] = ×6000 [1]. (b) 42 mm = 42 000 μm, and 42 000 ÷ 6000 [1] = 7 μm [1]. Examiner insight: An error carried forward from (a) is normally allowed in (b), so show the division even if you doubt your magnification.

6. (a) (8 × 10⁻⁵) ÷ (8 × 10⁻⁷) = 100 times [1]. (b) Two orders of magnitude [1]. (c) 8 × 10⁻⁵ m = 80 μm [1]. Examiner insight: An order of magnitude is a factor of 10, so “100” alone is not an answer to (b); the question asks how many powers of ten.

7. (a) A tail lets it swim to the egg [1]; many mitochondria release energy for the tail to move [1]; enzymes in the head digest a way into the egg [1]. (b) Xylem forms hollow tubes of dead cells [1], so water and mineral ions flow through freely [1]. (Also accept: walls strengthened with lignin, so the tubes do not collapse and they support the plant.) Examiner insight: Each mark needs a feature linked to what it does; “it has a tail” with no reason earns nothing on an “explain” question.

8. Folds increase the surface area of the membrane [1], so more substances can be absorbed at the same time [1]. Many mitochondria release energy by respiration [1], which is needed for active transport [1]. Examiner insight: This tests applying the “structure relates to function” idea to an unfamiliar cell; use the information given, and two linked pairs are needed for 4 marks.

9. (a) The cell gains different sub-cellular structures [1] that let it carry out a certain function, so it becomes specialised [1]. (b) Most animal cells differentiate at an early stage [1]; many plant cells keep the ability to differentiate throughout life [1]. In mature animals, cell division is mainly for repair and replacement [1]. Examiner insight: A “compare” answer needs both animals and plants named; a statement about one alone is not a comparison.

10. (a) Peel a thin layer of epidermis so light can pass through [1]. Add a drop of iodine solution to stain the cells [1]. Lower the coverslip at an angle to avoid air bubbles [1]. Start with the lowest-power objective and focus with the coarse, then fine, focus [1]. Change to a higher-power objective and refocus with the fine focus only [1]. Draw in pencil with clear lines, labels and a magnification scale [1]. (b) 10 × 40 = ×400 [1]. Examiner insight: A 6-mark method is marked on logical, ordered steps; “look at it under a microscope” earns nothing, and the magnification scale is a required feature of the drawing.

11. (a) Tape stops microorganisms from the air getting in [1]; upside down stops condensation dripping onto the agar [1]. (b) It reduces the chance of growing pathogens that could harm humans [1]. (c) Radii are 6 mm and 11 mm [1]; A: π × 6² = 113 mm² [1]; B: π × 11² = 380 mm² [1]. (d) 380 ÷ 113 = 3.36 times [1]. (e) Sterile water, to show that any clear zone is caused by the antiseptic and not the disc [1]. (f) Any two from: size of disc; soaking time; type of bacterium; incubation temperature; incubation time [1] [1]. Examiner insight: Using the diameter in πr² gives areas four times too big and loses the method mark; units (mm²) are expected on areas.

12. (a) 4 hours = 240 minutes, so 240 ÷ 20 = 12 divisions [1]; 250 × 2¹² = 1 024 000 [1] = 1.024 × 10⁶ bacteria [1]. (b) Nutrients run out, or toxic waste builds up, so division slows [1]. Examiner insight: The answer mark depends on standard form here; 1 024 000 scores 2 of 3 because the question asks for standard form.

Where marks are usually lost

• Dividing image size by real size without first putting both in the same unit.
• Writing “bacteria have no DNA” instead of “no nucleus”.
• Using diameter, not radius, in πr².
• Treating 4 hours of 20-minute divisions as 4 divisions instead of 12.
• Giving “optimum temperature” as the reason for incubating at 25°C.
• Naming an adaptation without the “so that…” that explains it.
• Saying an electron microscope is better only because it magnifies more, without resolution.
• In a method question, missing the coverslip angle, the order of focusing, or the magnification scale.

Next steps

• Recap with the Cell structure revision notes.
• Reread weak areas in the Cell structure study guide.
• Course hub: AQA GCSE Biology.
• Tick off topics on the printable checklist.
• Try all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

AQA GCSE Biology (8461) specification, for first teaching 2016, exams from 2018, version 1.0, published by AQA – section 4.1.1 Cell structure (4.1.1.1 to 4.1.1.6), with required practical activities 1 and 2.