5 high-yield, syllabus-aligned questions on Cell structure & function, covering 16 individually creditable mark points. Each one shows the answer that scores full marks under our guide, which phrase earns which mark, and a common incomplete answer — so you can see the difference rather than guess at it.
Free to read. No account needed for anything on this page.
Every question and solution is reviewed by examiners versed in WAEC and JAMB, each with more than thirty years of experience.
Mark allocations are TopMarks’ own, written against the published syllabus and Chief Examiners’ reports. They are a guide to how these answers are usually credited, not an official marking scheme.
State4 marks
State four differences between a plant cell and an animal cell.
TopMarks model answer
A plant cell has a cellulose cell wall, while an animal cell has only a cell membrane. A plant cell contains chloroplasts for photosynthesis; an animal cell has none. A mature plant cell has one large permanent central vacuole filled with cell sap, whereas an animal cell has only small temporary vacuoles or none. A plant cell has a fixed, regular shape while an animal cell has an irregular shape that can change.
Suggested marking guide
1Cell wall present in plant cell only
2Chloroplasts present in plant cell only
3Large permanent vacuole in plant cell
4Fixed regular shape versus irregular shape
Why it scores
Each mark requires the plant side AND the animal side. “Plant cells have a cell wall” is only half a difference; “a plant cell has a cell wall while an animal cell has only a membrane” is a whole one. This is the single most common way marks are lost on comparison questions across the whole of Biology.
A common incomplete answer
“Plant cells have a cell wall and chloroplasts.”
What it costs: Two marks of four, and only because the contrast is obvious enough to be inferred. The vacuole and the shape are not mentioned at all.
State the function of the mitochondrion and explain why muscle cells contain many of them.
TopMarks model answer
The mitochondrion is the site of aerobic respiration, in which glucose is oxidised to release energy that is stored as ATP. Muscle cells contract repeatedly and therefore have a very high energy demand. They contain many mitochondria so that enough ATP can be produced to meet that demand.
Suggested marking guide
1Site of aerobic respiration
2Releases energy stored as ATP
3Muscle cells have a high energy demand from contraction
Why it scores
“The powerhouse of the cell” is a phrase, not biology, and it earns nothing. The examiner wants the process named — aerobic respiration — the product named — ATP — and then the demand explained. Three named things, three marks.
A common incomplete answer
“Mitochondria release energy for the cell, and muscles need a lot of energy.”
What it costs: Two marks of three. Energy release and the muscle demand are credited, but aerobic respiration is never named, so the first mark is lost.
Key ideas to include: aerobic respiration, ATP, energy demand, contraction.
Define3 marks
Define osmosis.
TopMarks model answer
Osmosis is the movement of water molecules from a region of higher water potential, that is a dilute solution, to a region of lower water potential, that is a more concentrated solution, through a semi-permeable membrane.
Suggested marking guide
1Movement of water molecules
2From dilute to concentrated / high to low water potential
3Through a semi-permeable membrane
Why it scores
Three marks, and the third is the one that walks out of the exam hall unclaimed. Without the semi-permeable membrane the statement describes diffusion, not osmosis — the membrane is the ONLY thing that makes osmosis a distinct process. If you write nothing else, write the membrane.
A common incomplete answer
“Osmosis is the movement of water molecules from a dilute solution to a concentrated solution.”
What it costs: Two marks of three. Everything written is correct, and the one thing omitted — the semi-permeable membrane — is the definition’s whole point of difference from diffusion.
Key ideas to include: water molecules, water potential, dilute, concentrated, semi-permeable membrane.
Explain3 marks
Explain what happens when a red blood cell is placed in distilled water.
TopMarks model answer
Distilled water has a higher water potential than the cytoplasm of the red blood cell, so water enters the cell by osmosis through the cell membrane. The cell swells because it has no cell wall to resist the increase in volume. It eventually bursts, and this is called haemolysis.
Suggested marking guide
1Water enters by osmosis
2The cell swells because it has no cell wall
3The cell bursts — haemolysis
Why it scores
The middle mark is a reasoning mark, not a recall mark: the cell bursts BECAUSE it has no cell wall. A plant cell in the same distilled water becomes turgid and does not burst, and the examiner is checking that you know why the two behave differently.
A common incomplete answer
“The cell will burst.”
What it costs: One mark of three. The outcome is right, but osmosis is never named and the absence of a cell wall — the reason for the outcome — is never given.
Key ideas to include: water potential, osmosis, cell membrane, no cell wall, haemolysis.
Explain3 marks
Explain the difference between diffusion and active transport.
TopMarks model answer
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration, that is down the concentration gradient, while active transport moves substances against the concentration gradient, from a lower to a higher concentration. Diffusion is a passive process that requires no energy, whereas active transport requires energy supplied as ATP from respiration. Active transport also requires carrier proteins in the membrane, which diffusion does not.
Suggested marking guide
1Down the gradient versus against the gradient
2Passive and no energy versus energy as ATP
3Active transport needs carrier proteins
Why it scores
Two of these three marks are easy and one is not. Almost every candidate gets the energy difference. The carrier protein is what separates a 2 from a 3, and the direction relative to the concentration gradient must be stated in those words — “goes the other way” is not credited.
A common incomplete answer
“Diffusion does not need energy but active transport does need energy.”
What it costs: One mark of three. The energy difference is credited. Nothing is said about the concentration gradient or about carrier proteins.
Key ideas to include: concentration gradient, passive, against the gradient, ATP, carrier protein.
Practise Cell structure & function on real questions
Reading a full-mark answer is the first half. Writing one under time is the other. A free account opens exam-standard practice in Biology with the full solution on every question.