Cambridge International AS & A Level Biology 9700: Cells as the basic units of living organisms – 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 1.2, Cells as the basic units of living organisms, from Topic 1 Cell structure of the Cambridge International AS & A Level Biology 9700 syllabus for examination in 2025, 2026 and 2027: learning outcomes 1 to 7. It is AS Level content, examined on Papers 1 and 2, and Paper 4 can draw on it. Calculators are allowed in all 9700 papers. The questions here are different from those in the topic-level Cell structure practice questions, so use both.

Learn it first: 1.2 study guide · Recall: 1.2 revision notes · Course hub: Cambridge A Level Biology · Checklist: 9700 checklist

Questions

1. Name the structure described in each case.

(a) A dense region inside the nucleus, with no membrane, that makes ribosomal RNA. [1] (b) The partially permeable membrane around the large permanent vacuole of a plant cell. [1] (c) Narrow channels through the walls of neighbouring plant cells that link their cytoplasm. [1]

2. Name the two organelles of a eukaryotic cell that contain 70S ribosomes, and state one feature of their genetic material that they share with a typical bacterium. [3]

3. A muscle cell has many mitochondria.

(a) State the process in mitochondria that provides the cell with ATP. [1] (b) Name two energy-requiring processes in cells that use this ATP. [2]

4. All viruses are described as non-cellular.

(a) Name the two structures found in every virus. [2] (b) Some viruses have an extra outer layer. Name this layer and the type of molecule it is made of. [2] (c) State two structural features of a typical bacterium that a virus does not have. [2]

5. (calculator allowed) A transmission electron micrograph shows a rod-shaped cell. A scale bar labelled 0.5 µm measures 8 mm. The cell measures 52 mm long.

(a) Calculate the magnification of the micrograph. [2] (b) Calculate the actual length of the cell in µm. [2] (c) A student says the structure could be a mitochondrion. State two features visible in the micrograph that would show it is a bacterium. [2]

6. Compare the structure and function of cilia and microvilli. [4]

7. Animal cells contain centrioles and microtubules.

(a) Describe the structure of a centriole. [2] (b) State two functions of microtubules in a cell. [2]

8. (calculator allowed) A student counted the mitochondria visible in electron micrograph sections of five cells of each of two types. Cell type A comes from a tissue that absorbs substances by active transport. Cell type B is a fat-storage cell. The results are hypothetical.

Cell	1	2	3	4	5
Type A	24	31	27	29	34
Type B	9	12	8	11	10

(a) Calculate the mean number of mitochondria for each cell type. [2] (b) Calculate the percentage by which the mean for type A is greater than the mean for type B. [2] (c) Suggest an explanation for the difference. [2]

9. The Golgi body and lysosomes are found in animal cells.

(a) Describe the appearance of the Golgi body in a transmission electron micrograph. [2] (b) Outline how lysosomes are formed and what they do. [2]

10. A typical bacterium, a liver cell and a palisade mesophyll cell are compared.

(a) Copy and complete the table with a tick (present) or a cross (absent) for each cell. [5]

Feature	Bacterium	Liver cell	Palisade cell
Cell wall
Nucleus with nuclear envelope
80S ribosomes
Circular DNA
Chloroplasts

(b) A student sees 70S ribosomes in an electron micrograph and concludes that the cell must be prokaryotic. Explain why this conclusion is not valid. [2]

11. (calculator allowed) A transmission electron micrograph at × 12 000 shows a cell from the lining of a mammalian organ. It shows:

• a nucleus with an image diameter of 84 mm, containing a dark, dense region
• many parallel flattened membrane sacs covered with small dots
• a large curved stack of membrane sacs, with many vesicles near it and near the cell surface
• many oval organelles with two membranes, the inner one folded
• on one surface, a row of small finger-like folds of the membrane with no microtubules inside
• no cell wall, no chloroplasts and no large vacuole.

(a) Calculate the actual diameter of the nucleus in µm. [2] (b) Identify the finger-like folds and state their function. [2] (c) Give two pieces of evidence from the description that this is an animal cell, not a plant cell. [2] (d) Suggest, with a reason, what this cell produces in large amounts. [2]

Answers

1. (a) Nucleolus [1] (b) Tonoplast [1] (c) Plasmodesmata [1] Examiner insight: Naming questions reward the exact syllabus term; “vacuole membrane” for (b) or “pores” for (c) is unlikely to be accepted, and a misspelling that could be another structure (for example “nucleus” for nucleolus) scores zero.

2. Mitochondria [1]; chloroplasts [1]. Both contain small circular DNA, like a bacterium [1]. Examiner insight: “DNA” alone does not earn the third mark: the shared feature the syllabus names is that the DNA is small and circular, so the shape word must be there.

3. (a) Aerobic respiration [1] (b) Any two, one mark each: protein synthesis; active transport; muscle contraction; cell division; movement of vesicles. Muscle contraction [1]; protein synthesis [1]. Examiner insight: Avoid writing that respiration “makes energy” or “produces energy”: energy is released and transferred to ATP, and wording that says energy is created is usually not credited.

4. (a) A nucleic acid core (DNA or RNA) [1]; a protein capsid [1]. (b) An envelope [1] made of phospholipids [1]. (c) Any two, one mark each: cell wall of peptidoglycan; ribosomes (70S); cytoplasm; cell surface membrane. Peptidoglycan cell wall [1]; 70S ribosomes [1]. Examiner insight: In (a), “DNA and RNA” as the core is wrong: a virus has one or the other, so write “DNA or RNA” to keep the mark.

5. (a) 8 mm = 8000 µm; magnification = 8000 ÷ 0.5 [1] = × 16 000 [1] (b) Length = 52 mm ÷ 16 000 = 52 000 µm ÷ 16 000 [1] = 3.25 µm [1] (c) Any two, one mark each: a cell wall outside the membrane; no double membrane (envelope) around it; no cristae; ribosomes free in the cytoplasm; DNA free in the cytoplasm. Cell wall present [1]; no double membrane or cristae [1]. Examiner insight: Magnification has no units, so “× 16 000 µm” can lose the accuracy mark; allow error carried forward in (b) if a wrong magnification from (a) is used correctly.

6. Both are extensions of the cell surface covered by the cell surface membrane [1]. Cilia contain a 9 + 2 arrangement of microtubules, while microvilli have no microtubule core [1]. Cilia grow from a basal body, and microvilli do not; cilia are also much longer [1]. Cilia beat to move fluid or mucus across a surface, while microvilli increase the surface area for absorption [1]. Examiner insight: “Compare” needs both structures named in each point; separate descriptions of cilia, then of microvilli, usually score fewer marks than matched statements.

7. (a) A short hollow cylinder [1] made of nine triplets of microtubules arranged in a ring; centrioles occur in pairs at right angles [1]. (b) Any two, one mark each: form the spindle in cell division; form the cytoskeleton that supports the cell; move vesicles or organelles; form the core of cilia. Spindle formation [1]; cytoskeleton / moving organelles [1]. Examiner insight: “Nine microtubules” without “triplets” or “groups of three” is an incomplete structural point and may not get the second mark in (a).

8. (a) Type A: (24 + 31 + 27 + 29 + 34) ÷ 5 = 29 [1]; type B: (9 + 12 + 8 + 11 + 10) ÷ 5 = 10 [1] (b) (29 − 10) ÷ 10 × 100 [1] = 190% [1] (c) Active transport is an energy-requiring process that uses ATP [1]; type A cells need more ATP, which is made by aerobic respiration in mitochondria [1]. Examiner insight: In (b) the change is divided by the smaller value (type B); dividing by 29 gives about 66% and loses the accuracy mark, though the method mark may still be given if the subtraction is shown.

9. (a) A stack of flattened, curved membrane sacs [1], with vesicles at the edges [1]. (b) Lysosomes bud off from the Golgi body as vesicles [1]; they contain hydrolytic enzymes that digest worn-out organelles or material taken into the cell [1]. Examiner insight: Mentioning ribosomes on the Golgi body is a contradiction that cancels the mark: the dots belong to the RER, not the Golgi.

10. (a) One mark per correct row: Cell wall: ✓ ✗ ✓ [1] Nucleus with nuclear envelope: ✗ ✓ ✓ [1] 80S ribosomes: ✗ ✓ ✓ [1] Circular DNA: ✓ ✓ ✓ (in mitochondria, and in chloroplasts for the palisade cell) [1] Chloroplasts: ✗ ✗ ✓ [1] (b) Eukaryotic cells also contain 70S ribosomes inside mitochondria and chloroplasts [1], so the cell is only prokaryotic if it also has no nucleus and no double-membrane organelles [1]. Examiner insight: The circular DNA row needs care: the syllabus states that mitochondria and chloroplasts contain small circular DNA, so all three cells get a tick.

11. (a) 84 mm = 84 000 µm; 84 000 ÷ 12 000 [1] = 7 µm [1] (b) Microvilli [1]; they increase the surface area for absorption [1]. (c) Any two, one mark each: no cell wall; no chloroplasts; no large permanent vacuole; microvilli present. No cell wall [1]; microvilli present / no chloroplasts or large vacuole [1]. (d) Protein (for secretion) [1]; there is a lot of rough endoplasmic reticulum and a large Golgi body with many vesicles near the cell surface [1]. Examiner insight: In (c) the evidence must come from the description given; “it has centrioles” is not credited because the micrograph description does not mention them.

Where marks are usually lost

• Writing “DNA” instead of “small circular DNA” for mitochondria and chloroplasts.
• Treating 70S ribosomes as proof that a cell is prokaryotic.
• Giving units with a magnification, or not converting mm to µm before dividing.
• Dividing by the wrong value in a percentage change calculation.
• Writing separate descriptions in a “compare” question instead of matched points.
• Saying a virus core is “DNA and RNA”.
• Describing a centriole as nine single microtubules rather than nine triplets.
• Placing ribosomes on the Golgi body or on the SER.
• Using evidence that is not in the micrograph or description given.

Next steps

• 1.2 revision notes
• 1.2 study guide
• Cell structure study guide for the whole of Topic 1
• Cambridge A Level Biology hub
• 9700 printable checklist
• Free 9700 AS diagnostic
• Book a free trial class

Official syllabus

Cambridge International AS & A Level Biology 9700 syllabus for examination in 2025, 2026 and 2027, Cambridge University Press & Assessment – Topic 1, Cell structure (section 1.2 Cells as the basic units of living organisms).