Eukaryotes, prokaryotes and specialised cells – GCSE Biology exam questions with mark scheme

1Grade 1–33 marks

The diagram shows a plant cell.

(a) Name parts A and B. [2]

(b) Give the function of part C. [1]

(a) A: cell wall (allow cellulose cell wall; do not accept cell membrane)(1)
(a) B: nucleus(1)
(b) C (chloroplast) absorbs light for photosynthesis; accept site of photosynthesis / where photosynthesis happens / photosynthesis / contains chlorophyll to absorb light; ignore 'makes food' alone(1)
Answer: (a) A cell wall, B nucleus (b) absorbs light / site of photosynthesis
Examiner tip: The thick outer line is the cell wall, not the membrane — students who label it 'cell membrane' lose the mark.

2Grade 1–3Foundation4 marks

The table shows some structures found in cells.

Complete the table by putting a tick (✓) in each box where the structure is found in that type of cell. The first row has been done for you. [4]

Structure	Animal cell	Plant leaf cell	Bacterial cell
Cytoplasm	✓	✓	✓
Cell membrane
Nucleus
Plasmid
Chloroplast

Cell membrane: ticks in all three columns (animal, plant leaf, bacterial)(1)
Nucleus: ticks in animal cell and plant leaf cell only (no tick for bacterial cell)(1)
Plasmid: tick in bacterial cell only(1)
Chloroplast: tick in plant leaf cell only
Each row must be fully correct for the mark; an extra tick or a missing tick in a row = 0 for that row; allow crosses in empty boxes(1)
Answer: Cell membrane: all three; nucleus: animal and plant; plasmid: bacterial only; chloroplast: plant only
Examiner tip: Most lost marks come from forgetting that bacteria also have a cell membrane, or ticking 'nucleus' for bacteria.

3Grade 4–56 marks

(a) Draw one line from each specialised cell to the feature that helps it carry out its function. [3]

Specialised cell	Feature
Muscle cell	Contains chloroplasts to absorb light
Nerve cell	Long extension that gives a large surface area for absorbing water
Root hair cell	Long, with branched endings that connect to many other cells
	Contains protein fibres that slide over each other to shorten the cell

(b) What is meant by cell differentiation? [1]

(c) A gardener cuts a short piece of stem from a geranium plant and puts it in damp compost. After two weeks the cutting has grown new roots.

A person who loses the tip of a finger cannot grow a new fingertip.

Explain this difference between plants and animals. [2]

(a) Muscle cell → protein fibres that slide over each other to shorten the cell(1)
(a) Nerve cell → long, with branched endings that connect to many other cells(1)
(a) Root hair cell → long extension that gives a large surface area for absorbing water
More than one line from a cell = 0 for that cell(1)
(b) (the process by which) a cell changes / develops to become a specialised cell (to carry out a particular function); allow a cell gains the sub-cellular structures it needs for a particular job; ignore a cell divides alone(1)
(c) many plant cells keep the ability to differentiate throughout life / plants have (meristem) cells that can become any type of cell, so stem cells can become root cells; allow plant cells can still specialise in adults(1)
(c) most animal cells differentiate at an early stage (and cannot change type) / in adult animals cell division is mainly for repair and replacement (not to make new body parts); ignore animals do not have stem cells(1)
Answer: (a) muscle–sliding protein fibres; nerve–long with branched endings; root hair–large surface area for water (b) a cell becomes specialised for a particular function (c) plant cells keep the ability to differentiate all their lives; most animal cells differentiate early and adult cell division is only for repair/replacement
Examiner tip: In (c) you need a point about plants AND a point about animals: answers that only describe the plant miss the second mark.

4Grade 4–55 marks

The diagram shows a bacterial cell.

(a) Name the structures labelled X and Y. [2]

(b) The small dots in the cytoplasm are ribosomes. Give the function of a ribosome. [1]

(c) Give two ways the genetic material in this bacterial cell is different from the genetic material in an animal cell. [2]

(a) X: (single) loop of DNA; allow DNA / chromosomal DNA / genetic material / circular chromosome; do not accept nucleus(1)
(a) Y: plasmid; allow small ring of DNA(1)
(b) (site of) protein synthesis; allow makes proteins / joins amino acids together; ignore makes enzymes alone(1)
(c) any one from: not enclosed in a nucleus / free in the cytoplasm; it is a single loop (of DNA) (not separate chromosomes)(1)
(c) has plasmids / small rings of DNA as well as the main DNA; allow the other point from the list above if not already given
Comparative statements must refer to the bacterial cell, e.g. 'animal cells have a nucleus' alone = 1 mark only if the idea of 'bacteria do not' is clear(1)
Answer: (a) X loop of DNA, Y plasmid (b) protein synthesis (c) any two of: not in a nucleus / single loop / has plasmids
Examiner tip: Never call the DNA loop a 'nucleus': the defining feature of a prokaryote is that its DNA is NOT in a nucleus.

5Grade 6–74 marks

The table shows the typical sizes of three structures.

Structure	Typical size
Palisade cell (length)	100 µm
Bacterium (length)	1 µm
Ribosome (diameter)	20 nm

$1\ \mu\text{m} = 1 \times 10^{-6}\ \text{m}$ and $1\ \text{nm} = 1 \times 10^{-9}\ \text{m}$

(a) Give the diameter of the ribosome in metres. Give your answer in standard form. [1]

(b) Calculate how many ribosomes would fit side by side along the length of the bacterium. [2]

(a) $2 \times 10^{-8}$ (m); allow $2.0 \times 10^{-8}$; do not accept $20 \times 10^{-9}$ (not standard form)(1)
(b) $1 \times 10^{-6} \div 2 \times 10^{-8}$ OR $1000\ \text{nm} \div 20\ \text{nm}$ (sizes in the same units)(1)
(b) 50; correct answer with no working = 2 marks(1)
(c) 2; allow $10^{2}$ / 100 times longer(1)
Answer: (a) $2 \times 10^{-8}$ m (b) 50 (c) 2 orders of magnitude
Examiner tip: Convert both sizes to the same unit before dividing; mixing µm and nm gives an answer 1000 times too big or too small.

6Grade 4–54 marks

The diagram shows a human sperm cell.

(a) Part Q is packed with mitochondria. Explain how this helps the sperm cell to carry out its function. [2]

(b) Part P contains enzymes. Suggest how these enzymes help the sperm cell. [2]

(a) mitochondria carry out (aerobic) respiration, which releases / transfers energy; do not accept produces / makes / creates energy(1)
(a) (energy) for the tail to move / for the sperm to swim (to the egg)(1)
(b) enzymes digest / break down the outer layer / membrane / coat of the egg (cell); ignore 'break into the egg' without the idea of digestion(1)
(b) so the sperm (head / nucleus) can get into / penetrate the egg (to fertilise it); allow so the nuclei can fuse(1)
Answer: (a) respiration in the mitochondria releases energy for the tail to move / swim (b) digest the outer layer of the egg so the sperm can enter it
Examiner tip: Write 'releases energy', never 'makes energy' — the first mark is lost for 'produces energy'.

7Grade 6–7Higher4 marks

Xylem cells and phloem cells are both specialised cells found in plant stems.

Compare the structure of xylem cells with the structure of phloem cells.

In your answer, explain how each type of cell is adapted to its function. [4]

Xylem structure: xylem cells are dead / hollow / have no cytoplasm and no end walls, forming a continuous tube; OR walls strengthened with lignin(1)
Xylem function link: so water and mineral ions can flow (up the plant) without obstruction; OR lignin makes them strong so they withstand pressure / do not collapse / support the plant(1)
Phloem structure: phloem cells are living / contain cytoplasm, joined end to end with pores (sieve plates) in their end walls; allow elongated cells; allow companion cells(1)
Phloem function link: so cell sap / dissolved sugars can move from one phloem cell to the next (up or down the plant / translocation)
Max 2 marks if only xylem or only phloem is described; each function mark must be linked to a correct structural feature of that cell(1)
Answer: Xylem: dead, hollow, no end walls, lignified – continuous strong tube for water and minerals. Phloem: living elongated cells with pores in end walls – dissolved sugars move cell to cell.
Examiner tip: A comparison needs both cell types: write a xylem feature AND the matching phloem feature, each with a 'so that…' link to function.

8Grade 6–75 marks

Scientists estimated the mean number of mitochondria in four types of human cell. The bar chart shows the results.

Mature red blood cells have no mitochondria.

(a) Calculate how many times more mitochondria there are in a heart muscle cell than in a liver cell. Give your answer to 2 significant figures. [2]

(b) Explain why heart muscle cells contain so many mitochondria. [2]

(c) Mature red blood cells also have no nucleus. Suggest one advantage to a red blood cell of having no nucleus and no mitochondria. [1]

(a) $5000 \div 1500$(1)
(a) 3.3; allow 3.33 for 1 mark only if not rounded to 2 s.f. (i.e. award M1 only); correct answer with no working = 2 marks(1)
(b) (aerobic) respiration takes place in mitochondria, releasing energy; do not accept produces / makes energy(1)
(b) heart muscle contracts continuously / all the time / needs a lot of energy to contract (to pump blood)(1)
(c) more space for haemoglobin, so it can carry more oxygen; allow it does not use up the oxygen it is carrying; ignore 'smaller' / 'more flexible' alone(1)
Answer: (a) 3.3 (b) respiration in mitochondria releases energy; heart muscle contracts constantly so needs lots of energy (c) more room for haemoglobin to carry oxygen
Examiner tip: Read both bars against the gridlines (1500 sits on a minor gridline) and round to 2 significant figures as asked.

9Grade 6–76 marks

A palisade cell from a leaf is about 100 µm long. A typical bacterial cell is about 1 µm long.

Compare the structure of a palisade cell with the structure of a bacterial cell. [6]

Similarity: both have a cell membrane(1)
Similarity: both have cytoplasm (with ribosomes for protein synthesis)(1)
Similarity: both have a cell wall (the palisade cell wall is made of cellulose)(1)
Similarity: both contain genetic material / DNA(1)
Difference: the palisade cell is eukaryotic, so its DNA is enclosed in a nucleus; the bacterial cell is prokaryotic, so it has no nucleus and its DNA is a single loop free in the cytoplasm; do not credit 'bacteria have a nucleus'(1)
Difference: the bacterial cell may contain plasmids (small rings of DNA); the palisade cell does not(1)
Difference: the palisade cell has (many) chloroplasts for photosynthesis; the bacterial cell has none(1)
Difference: the palisade cell has mitochondria; the bacterial cell has none(1)
Difference: the palisade cell has a permanent vacuole containing cell sap; the bacterial cell does not(1)
Difference: the palisade cell is about 100 times longer / 2 orders of magnitude bigger than the bacterial cell(1)

Level	Marks	What it looks like
Level 3	5–6	A detailed comparison giving both similarities and differences. Differences are written as linked pairs (what one cell has and what the other has instead or lacks), including where the genetic material is found in each cell. May include a size comparison.
Level 2	3–4	Some correct similarities and/or differences, with some linked comparison, but may be mainly separate lists of structures for each cell or miss the position of the genetic material.
Level 1	1–2	Simple statements about the structures of one or both cells with little or no comparison; may contain errors.
No marks	0	No relevant content.

Answer: Both have a cell membrane, cytoplasm (with ribosomes), a cell wall and DNA. The palisade cell's DNA is in a nucleus; the bacterium's is a single loop in the cytoplasm, plus plasmids. Only the palisade cell has chloroplasts, mitochondria and a permanent vacuole, and its wall is cellulose. The palisade cell is about 100 times (2 orders of magnitude) longer.
Examiner tip: 'Compare' needs similarities as well as differences, and each difference written as a pair ('the palisade cell has…, but the bacterial cell…'); two separate lists of parts rarely get above Level 2.

10Grade 8–9Higher5 marks

A student looked at three different cells, A, B and C, using electron micrographs. The table shows the student's observations.

Feature	Cell A	Cell B	Cell C
Cell wall	present	present	absent
Nucleus	present	absent	present
Mitochondria	present	absent	present
Chloroplasts	absent	absent	absent
Permanent vacuole	present	absent	absent
Length in µm	120	3	20

(a) Which cell, A, B or C, is a prokaryotic cell? Give two reasons for your answer using the table. [2]

(b) Another student says:

“Cell A cannot be a plant cell, because it has no chloroplasts.”

Evaluate this statement. [3]

(a) (cell B) has no nucleus / its genetic material is not in a nucleus; allow no mitochondria(1)
(a) (cell B) is much smaller / only 3 µm long / about 40 times shorter than A / an order of magnitude smaller than the eukaryotic cells
Both marks require cell B to be identified; reasons must be different (e.g. 'no nucleus' and 'no mitochondria' can both score if size not given)(1)
(b) the statement is wrong / cell A could be a plant cell(1)
(b) cell A has a (cellulose) cell wall and a permanent vacuole (and a nucleus), which are features of plant cells; allow the cell wall alone is not enough evidence because bacteria also have cell walls(1)
(b) not all plant cells have chloroplasts / cells in parts that get no light, e.g. root (hair) cells, have no chloroplasts
Allow a balanced conclusion, e.g. 'cell A is probably a plant root cell, but it could be another organism with a cell wall', for the first mark(1)
Answer: (a) B: no nucleus (no mitochondria) and much smaller (3 µm) (b) The statement is wrong: A has a cell wall and permanent vacuole like a plant cell, and plant cells that receive no light (e.g. root cells) have no chloroplasts.
Examiner tip: 'Evaluate' needs a judgement: say whether the statement is right or wrong, then back it up with evidence from the table and a reason why some plant cells lack chloroplasts.

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