Overview
What you’ll learn
- Label animal, plant and bacterial cells and link every part to its job.
- Put cells, organelles and DNA into order-of-magnitude size order with the right prefixes.
- Explain how sperm, nerve, muscle, root hair, xylem and phloem cells are adapted to their roles.
- Describe the microscopy required practical and calculate magnification with clean unit conversion.
- Order the events of the cell cycle and explain why mitosis keeps cells genetically identical.
- Compare embryonic, adult and meristem stem cells and weigh up therapeutic cloning.
Specification checklist (AQA Trilogy 8464 · Edexcel 1SC0 · OCR Gateway J250)
Statements are paraphrased from the shared DfE combined science subject content and grouped by tier. Foundation content is studied by every student; Higher statements are examined on Higher-tier papers only. This chapter covers only what Combined Science (double award) examines — separate-science extras live on the GCSE Biology, Chemistry and Physics hubs. QuizQuip is not affiliated with AQA, Pearson Edexcel or OCR.
Foundation — every student
- 1.1Describe plant and animal cells (eukaryotic cells) as having a cell membrane, cytoplasm and genetic material enclosed in a nucleus, and bacterial cells (prokaryotic cells) as much smaller, with cytoplasm and a cell membrane surrounded by a cell wall, and genetic material that is a single DNA loop not enclosed in a nucleus, plus plasmids.
- 1.2Explain how the main sub-cellular structures — nucleus, cell membrane, mitochondria, ribosomes, and in plant cells chloroplasts and a permanent vacuole plus a cellulose cell wall — are related to their functions.
- 1.3Use estimations to explain the relative size and scale of cells, including order-of-magnitude calculations in standard form and the prefixes centi, milli, micro and nano.
- 1.4Explain how the structures of specialised cells — sperm, nerve and muscle cells; root hair, xylem and phloem cells — relate to their functions, and describe cells becoming specialised by differentiation.
- 1.5Carry out the microscopy required practical: use a light microscope to observe, draw and label a selection of plant and animal cells, including a magnification scale, and explain why electron microscopes gave scientists a clearer picture of sub-cellular structures.
- 1.6Use the equation magnification = image size ÷ real size, converting between centimetres, millimetres, micrometres and nanometres.
- 1.7Describe the nucleus as containing chromosomes made of DNA molecules, with each chromosome carrying a large number of genes; in body cells chromosomes are normally found in pairs.
- 1.8Describe the cell cycle: before a cell divides it grows and copies its DNA, during mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides, and finally the cytoplasm and cell membrane divide to form two identical cells — important for the growth and development of multicellular organisms.
- 1.9Describe the function of stem cells in embryonic tissue, in adult bone marrow and in the meristems of plants, and evaluate the benefits and risks of using stem cells in medicine, including therapeutic cloning in which an embryo is produced with the same genes as the patient.
Key points
- 1Eukaryotic cells (animals, plants, algae, fungi) keep DNA in a nucleus; prokaryotic cells (bacteria) are far smaller, have no nucleus, a single DNA loop and plasmids.
- 2Animal cell kit: nucleus · cytoplasm · cell membrane · mitochondria · ribosomes. Plant cells add chloroplasts, a permanent vacuole and a cellulose cell wall.
- 3Function map: nucleus stores DNA · membrane controls what enters and leaves · mitochondria release energy in respiration · ribosomes build proteins · chloroplasts trap light for photosynthesis.
- 4Specialisation = differentiation: sperm have a streamlined tail and many mitochondria, nerve cells are long with branching connections, root hair cells have a huge surface area.
- 5Magnification = image size ÷ real size; 1 cm = 10 mm, 1 mm = 10⁻³ m, 1 µm = 10⁻⁶ m, 1 nm = 10⁻⁹ m.
- 6Electron microscopes beat light microscopes on both magnification and resolution — that is how organelles were mapped.
- 7Cell cycle: growth + DNA copying → mitosis → cytoplasm and membrane divide → two genetically identical cells; body-cell chromosomes come in pairs.
- 8Stem cells are undifferentiated: embryonic cells can become almost any cell type, adult bone marrow makes blood cells, and meristems keep dividing for life — the basis of plant cloning.
Notes · 1 of 6
Eukaryotes and prokaryotes
Two cell designs: one keeps its DNA in a nucleus, the other lets it float in a loop.
Every organism is built from cells, and every cell follows one of two plans. Eukaryotic cells — animals, plants, algae and fungi — enclose their genetic material inside a nucleus. Prokaryotic cells — bacteria — are much smaller and keep a single loop of DNA free in the cytoplasm, often alongside tiny rings of DNA called plasmids that can be swapped between bacteria. Exam answers earn marks for naming the plan and the organism it belongs to.
| Feature | Eukaryotic cell (plant, animal, algal, fungal) | Prokaryotic cell (bacteria) |
|---|---|---|
| Nucleus | Yes — DNA stored inside it | No — DNA loose in the cytoplasm |
| Genetic material | Chromosomes made of DNA | One circular DNA loop, plus plasmids |
| Typical size | About 10–100 µm | About 1–2 µm — tens of times smaller |
| Cell wall | Plants and algae (cellulose); fungi (chitin) | Always present, but not made of cellulose |
| Mitochondria and chloroplasts | Mitochondria in almost all; chloroplasts in plants and algae | Neither — no membrane-bound organelles |
| Plasmids | Absent | Usually one or more small DNA rings |
Size ladder worth memorising
1 cm = 10 mm = 10 000 µm = 10 000 000 nm. A human hair is roughly 100 µm across, a cheek cell about 60 µm, and a bacterium around 2 µm — so about thirty bacteria would line up across one cheek cell.
Notes · 2 of 6
Animal and plant cells
Same basics, three plant extras — and every part has a job you must be able to name.
| Structure | Found in | Function |
|---|---|---|
| Nucleus | Plant and animal cells | Stores genetic material; controls the cell’s activities |
| Cytoplasm | Plant and animal cells | Jelly where most reactions happen |
| Cell membrane | Plant and animal cells | Controls what enters and leaves the cell |
| Mitochondria | Plant and animal cells | Site of aerobic respiration, transferring energy from glucose |
| Ribosomes | Plant and animal cells | Build proteins |
| Chloroplasts | Plant cells (and algae) | Absorb light for photosynthesis |
| Permanent vacuole | Plant cells | Sap-filled space that keeps the cell rigid |
| Cellulose cell wall | Plant cells | Strengthens and supports the cell |
The trick examiners look for is the link between structure and function. Mitochondria are folded and crowded because respiration enzymes live there; the vacuole pushes outwards so leaves stay firm; the cell wall is a mesh of cellulose that stops the cell bursting when it takes in water. “Chloroplasts are green” earns nothing — “chloroplasts contain chlorophyll which absorbs light for photosynthesis” earns the mark.
Notes · 3 of 6
Specialisation and differentiation
Cells finish up shaped for one job — and the shape is the mark scheme.
Most animal cells differentiate early in development; many plant cells keep dividing and differentiating for life. A specialised cell has a structure that fits its function, and every GCSE answer pairs the structure with the job it does:
Sperm cell
Streamlined swimmer
A long tail for propulsion, many mitochondria to power it, enzymes in the head to help enter the egg, and half the chromosomes of a body cell.
Nerve cell
Long-distance wire
An elongated axon carries impulses over long distances, and branched endings connect to many other cells.
Muscle cell
Contractile fibre
Packed with mitochondria to release energy for contraction, and stores of glycogen that break down to glucose in exercise.
Root hair cell
Absorption expert
A tiny finger-like projection multiplies surface area for taking up water and mineral ions.
Xylem cell
Dead water pipe
Hollow, strengthened tubes carry water and dissolved minerals up the plant.
Phloem cell
Living food line
End walls with small pores let dissolved sugars flow to where they are needed.
Notes · 4 of 6
The microscopy required practical
Method, risks, magnification maths and what electron microscopes added.
- 11. Peel and mount
Peel a thin layer of onion epidermis (plant) or scrape cheek cells (animal) onto a drop of water on a slide.
- 22. Stain
Add two drops of iodine solution (plant) or methylene blue (animal) so the nucleus and other parts stand out.
- 33. Cover
Lower a cover slip slowly at an angle so air bubbles are pushed out — bubbles hide the specimen.
- 44. Focus low, then high
Start with the lowest-power objective; use the coarse focus first, then the fine focus at higher power.
- 55. Draw and scale
Draw what you see with a sharp (not sketchy) pencil line, label the parts, and add a magnification scale such as “×400”. The drawing should be at least 5 cm across.
Risks and controls
Iodine and methylene blue stain skin and clothes — wear eye protection and wash splashes straight away. Cover slips and slides are glass: handle carefully and dispose of sharp waste in the designated bin. Cheek-cell samples come from inside your body: used mouth-exit paper towels go in the disposal bag, never the bin.
Typical results: at ×100 you can see the cell wall, cytoplasm and nucleus of onion cells clearly; at ×400 the nucleus looks larger and the vacuole boundary is easy to draw. Resolution limits how much detail appears: two structures closer together than the resolution limit blur into one. Electron microscopes use beams of electrons instead of light, giving far higher magnification and resolution — that is how ribosomes, mitochondria details and plasmids were discovered.
Exam tips
- Worked example — magnification of a drawing. A student draws an onion cell 42 mm long. The real cell is 0.21 mm long. Magnification = image size ÷ real size = 42 ÷ 0.21 = ×200. Both lengths were already in millimetres, so no conversion was needed — check the units before you divide.
- Worked example — converting before dividing. A drawing of a chloroplast measures 36 mm. The real chloroplast is 120 µm long. Convert first: 36 mm = 36 000 µm. Then magnification = 36 000 ÷ 120 = ×300. Dividing millimetres by micrometres without converting gives a nonsense ×0.3 — the classic slip.
- Worked example — real size from a magnification. A mitochondrion is drawn 18 mm long at a magnification of ×600. Real size = image size ÷ magnification = 18 ÷ 600 = 0.03 mm. Convert: 0.03 mm = 30 µm. State the final unit — a bare 0.03 loses the mark.
Notes · 5 of 6
Chromosomes, the cell cycle and mitosis
Copy the DNA, pull the copies apart, split the cell — in that order, every time.
The nucleus stores chromosomes — long strands of DNA carrying hundreds of genes each. Body cells hold chromosomes in matching pairs: a human body cell has 46 chromosomes, i.e. 23 pairs. Before a cell can divide it must copy the DNA so each new cell gets a full set.
| Stage | What happens | Why it matters |
|---|---|---|
| 1 · Growth and DNA copying | The cell grows, doubles its organelles and copies its DNA | Each daughter cell needs a full set of instructions |
| 2 · Mitosis | One set of chromosomes is pulled to each end of the cell and the nucleus divides | Keeps the chromosome number constant |
| 3 · Cytokinesis | The cytoplasm and cell membrane divide | Two genetically identical cells are produced |
Mitosis matters wherever cells must be identical: growth of a seedling, repair of a scraped knee, and replacement of worn-out skin and gut lining. Because the copies are pulled to opposite ends before the cell splits, each new cell carries the same number and type of chromosomes as the parent.
Notes · 6 of 6
Stem cells and therapeutic cloning
Undifferentiated cells from embryos, bone marrow and meristems — and the debate around them.
| Source | What the cells can become | Typical use |
|---|---|---|
| Human embryo | Almost any cell type | Research; potential transplants made by therapeutic cloning |
| Adult bone marrow | Mainly blood cells | Treating leukaemia and some blood disorders by transplant |
| Plant meristem | Any plant cell type, for the plant’s whole life | Cloning rare plants and producing crop copies quickly |
In therapeutic cloning, an embryo is produced with the same genes as the patient, so cells made from it would not be rejected when transplanted. The benefits — treating paralysis, diabetes and blood cancers — are weighed against objections: embryos are potential lives, and unregulated clinics carry infection or rejection risks. Meristem cloning avoids the ethical issue entirely, which is why plant nurseries use it commercially.
Revise
Key terms
The words examiners expect you to use precisely.
- Eukaryotic cell
- A cell that stores its genetic material inside a nucleus; plants, animals, algae and fungi.Contrast with prokaryotes in every compare question.
- Prokaryotic cell
- A small cell, such as a bacterium, with a single DNA loop and plasmids but no nucleus.
- Plasmid
- A small ring of DNA in a bacterium, separate from the main DNA loop.
- Differentiation
- The process by which a cell gains structures to become specialised for its job.
- Mitosis
- Cell division that pulls one set of chromosomes to each end of the cell, producing two genetically identical cells.
- Stem cell
- An undifferentiated cell that can divide and develop into other cell types.
Show 1 more key termShow fewer key terms
- Magnification
- How many times bigger an image is than the real object: image size ÷ real size.
Revise
Common mistakes
Where students most often lose marks in this chapter — and what to do instead.
Mistake: Saying bacteria have a nucleus
Prokaryotic DNA sits free in the cytoplasm as a single loop.
Instead: Prokaryotes have no nucleus — “single DNA loop plus plasmids” is the full-credit phrase.
Mistake: Giving chloroplasts to animal cells
Animal cells have no photosynthesis machinery.
Instead: Chloroplasts appear in plant cells and algae only.
Show 10 more mistakesShow fewer mistakes
Mistake: Writing magnification with units (×400 µm)
Magnification is a ratio of two lengths in the same units, so units cancel.
Instead: Magnification is written ×400 or “×400 magnification” — never with a length unit.
Mistake: Dividing real size by image size
It flips the magnification equation and gives a number below 1.
Instead: Magnification = image size ÷ real size; rearrange only after writing the equation.
Mistake: Mixing millimetres and micrometres mid-calculation
A 1000× error smuggles itself into the working.
Instead: Convert everything to one unit first, then divide.
Mistake: Saying mitosis makes gametes
Gamete production is a different division that halves the chromosome number.
Instead: Mitosis produces identical body cells for growth, repair and replacement.
Mistake: Ordering the cell cycle as mitosis → copy → split
The DNA copy happens first, before any pulling apart.
Instead: Growth and DNA copying, then mitosis, then cytoplasm and membrane division.
Mistake: Claiming adult bone marrow cells become any cell type
Adult stem cells are partly limited in what they can form.
Instead: Bone marrow stem cells mainly make blood cells; embryonic cells are the flexible ones.
Mistake: Saying electron microscopes just magnify more
Resolution — telling close structures apart — improved too.
Instead: Electron microscopes improved both magnification and resolution.
Mistake: Forgetting the cover-slip angle in the practical
Dropping it flat traps air bubbles that obscure the field of view.
Instead: Lower the cover slip at an angle to push air out.
Mistake: Using the coarse focus knob on high power
The big jump can crack the slide or lens.
Instead: Coarse focus at low power; fine focus only at higher powers.
Mistake: Describing therapeutic cloning as rejected-free without reason
The claim needs the genetic-match explanation for the mark.
Instead: A cloned embryo has the patient’s genes, so transplants from it are not rejected.
Check yourself
Quick quiz
20 questions with instant explanations. About 5 minutes.
Question 1 of 3· free preview of 20
- Question 1: current question
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- Question 3: not answered
Explain eukaryotes and prokaryotes
A bacterium is best described as a prokaryote because it
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Practise
Topical questions
12 exam-style questions with model answers and mark schemes.
A set of structured and calculation questions matched to this chapter, in three tiers, each with a model answer, mark scheme and examiner tip. Higher-tier questions are tagged.
Practise topical questionsExam practice
Practice paper
A 30-mark paper in the style of a Combined Science paper, with a separate mark scheme. Give yourself 40 min.
Question paper
Chapter 1 Practice Paper
30 marks · 40 min · 5 pages
6 multiple-choice questions and structured questions with answer lines. Cells and cell division: eukaryotes and prokaryotes, animal and plant cells, specialisation, the microscopy required practical, mitosis and the cell cycle, stem cells.
Mark scheme
PROChapter 1 Practice Paper — mark scheme
Answers · Marking points · 3 pages
Model answers with a mark for each creditworthy point — for marking at home or in class.
How does this chapter fit the real exams?
Biology Paper 1
1 h 15 · 70 marks (Trilogy)
Cell biology, organisation, infection and response, bioenergetics (chapters 1–7)
Biology Paper 2
1 h 15 · 70 marks (Trilogy)
Homeostasis, inheritance variation and evolution, ecology (chapters 8–10)
Tiers
Foundation (grades 1-1 to 5-5) · Higher (4-3 to 9-9)
Two grades are awarded together; the 21 required practicals are examined on the written papers
Want a full paper? Try the Biology Paper 1-style (Foundation), Biology Paper 1-style (Higher), Biology Paper 2-style (Foundation), Biology Paper 2-style (Higher), Chemistry Paper 1-style (Foundation), Chemistry Paper 1-style (Higher), Chemistry Paper 2-style (Foundation), Chemistry Paper 2-style (Higher), Physics Paper 1-style (Foundation), Physics Paper 1-style (Higher), Physics Paper 2-style (Foundation), Physics Paper 2-style (Higher), Required practicals practice sets.
Questions
Frequently asked questions
Is this chapter part of GCSE Combined Science (Trilogy)?
Yes. Cells and cell division is core Combined Science content in the DfE subject content shared by AQA Trilogy (8464), Pearson Edexcel (1SC0) and OCR Gateway (J250). Only separate-science extras such as culturing microorganisms are missing, and those never appear on combined papers.
Which paper examines this chapter?
Cell biology is examined on Biology Paper 1 (AQA Trilogy paper 1, Edexcel Biology paper 1, OCR Gateway Biology paper 1), together with organisation, infection and response, and bioenergetics.
Do I need the magnification equation for Foundation?
Yes. Magnification = image size ÷ real size with millimetre–micrometre conversion is assessed at both tiers. Higher papers usually hide an extra conversion step, such as a final answer in nanometres.
How is Combined Science different from triple GCSE Biology?
Combined Science is a double award with shorter, merged papers covering all three sciences. Triple Biology goes deeper — adding topics such as monoclonal antibodies, the brain and the eye, the kidney and plant hormones — and awards three separate grades. Everything on this page is needed for both routes.
Do stem-cell evaluation questions need both sides?
Yes. A strong answer gives a benefit (flexible embryonic cells), a limitation or objection (embryo ethics, infection risk) and a conclusion. One-sided answers cap at half marks.
Up next
Chapter 2: Transport in cells