Eukaryotes and prokaryotes & Animal and plant cells (incl. RP1)

SPEC 8461 · MODULE 1 · CELL BIOLOGY

Eukaryotes, Prokaryotes & Cell Types

In June 2024, students were asked to name a sub-cellular structure in a plant cell. The mark scheme accepted only one answer: "(permanent) vacuole." Students who wrote "fluid sac" or "water store" scored zero. In 10 minutes, you'll know every named structure — in exam wording.

Learning Objectives

By the end of this lesson, you'll be able to:

Identify and compare the sub-cellular structures of eukaryotic and prokaryotic cells

Explain the differences between animal cells, plant cells, and bacterial cells — including structures unique to each

Use the correct AQA mark-scheme wording for every sub-cellular structure

Spec Ref & Paper

Spec 4.1.1.1–4.1.1.2 · Paper 1 · Higher Tier. Cell structure questions appear on every Paper 1. Getting terminology right is the difference between 0 and full marks.

Two Types of Cell

Every living organism has cells that are either eukaryotic or prokaryotic. This distinction is the foundation of all of Module 1.

EUKARYOTIC

A cell whose genetic material is enclosed in a nucleus.

Includes: animal cells, plant cells, fungal cells, and protist cells. Typically 10–100 µm in size.

PROKARYOTIC

A cell whose genetic material is NOT enclosed in a nucleus — it is a single DNA loop in the cytoplasm.

May also have small extra rings of DNA called plasmids. Bacteria are prokaryotic. Typically 1–10 µm — much smaller than eukaryotic cells.

Mark-Scheme Language

For prokaryotes, the mark scheme credits "single loop of DNA" or "single circular DNA molecule." Do NOT write "circular chromosome" — bacterial DNA is not packaged into chromosomes.

Animal Cell

Most animal cells are eukaryotic and share the same five sub-cellular structures — all five appear in exam diagrams for identification and function questions.

Why "Most"?

The AQA spec says "most animal cells" — not all. Some specialised cells lack certain structures. Red blood cells, for example, have no nucleus. Learn the five as the standard set, and note that exceptions exist.

Animal Cell — 5 Structures

Five structures. Every one is examinable for both name and function. Learn both together.

StructureFunction — mark-scheme wording

NucleusContains chromosomes (DNA); controls the cell's activities

CytoplasmJelly-like substance; site of most chemical reactions

Cell membranePartially permeable; controls what enters and leaves the cell

MitochondriaSite of aerobic respiration; releases energy from glucose

RibosomesSite of protein synthesis

Energy Language — All Series

Mark schemes explicitly reject "energy is produced / made / created." Always write "energy is released" or "energy is transferred."

Common Misconception

Plants have mitochondria too. Plant cells photosynthesise AND respire — they need mitochondria to release energy for cell processes, exactly like animal cells. Examiner reports flag this error every series.

Plant Cell

Plant cells have all 5 animal cell structures, plus 3 extra. The large central space (vacuole) and thick outer border (cell wall) are the key visual identifiers.

Plant Cell — 8 Structures

Plant cells have everything animal cells have, plus three additional structures. Algal cells are treated identically by AQA.

Shared with Animal Cells (5)

Nucleus

Cytoplasm

Cell membrane

Mitochondria

Ribosomes

Plant Only — 3 Extra

Cell wall — made of cellulose; strengthens the cell

Permanent vacuole — filled with cell sap; maintains turgor

Chloroplasts — contain chlorophyll; site of photosynthesis — only in green parts of the plant (e.g. leaf cells, not root cells)

"Permanent Vacuole" — Mark-Scheme Alert

Both words matter. Animal cells can have small temporary vacuoles. "Permanent" distinguishes the plant cell structure. "Fluid sac" and "water store" score zero — they describe but do not name.

Bacterial Cell (Prokaryotic)

Bacteria are prokaryotes — no nucleus. Smaller than eukaryotic cells (1–10 µm). Three features unique to bacteria: DNA loop, plasmids, and cell wall made of a non-cellulose polymer.

Bacterial Cell Structures

Know what is present, what is absent, and how to write the DNA description correctly.

Present in Bacteria

Cell wall — different polymer to plant cellulose

Cell membrane — same function as eukaryotes

Cytoplasm — same function

Single circular DNA molecule — in the cytoplasm, not in a nucleus

Plasmids — small extra rings of DNA

Ribosomes — protein synthesis (smaller than eukaryotic ribosomes)

Absent in Bacteria

No nucleus

No mitochondria

No chloroplasts

No permanent vacuole

Key Trap

Never write "bacterial cell wall is made of cellulose." Plant cell walls → cellulose. Bacterial cell walls → different polymer (you don't need to name it).

Cell Type Comparison

StructureAnimal CellPlant CellBacterial Cell

Nucleus✔✔✘ (DNA loop instead)

Cell membrane✔✔✔

Cytoplasm✔✔✔

Ribosomes✔✔✔ (smaller)

Mitochondria✔✔✘

Cell wall (cellulose)✘✔✘ (diff. polymer)

Permanent vacuole✘✔✘

Chloroplasts✘✔ (green parts)✘

DNA loop + plasmids✘✘✔

4 Features All Cells Share

Every cell — animal, plant, or bacterial — has these four: cell membrane, cytoplasm, ribosomes, and genetic material (DNA). This is the answer to any "give a similarity between prokaryotic and eukaryotic cells" question.

Worked Example

A diagram shows a plant cell with three parts labelled X, Y and Z. Part X is the large fluid-filled space inside the cell. Part Y is the outer rigid layer surrounding the cell. Part Z contains the cell's chromosomes.

Name parts X, Y and Z.3 MARKS

Pattern — Recall (AO1)

Step 1: The command word is "name" — write the named term exactly. Descriptions score zero.

Step 2: Match each description to its structure: large fluid-filled space = permanent vacuole; outer rigid layer = cell wall; contains chromosomes = nucleus.

Step 3: Use AQA wording — "permanent vacuole" not "fluid sac." "Cell wall" not "outer casing."

X

(permanent) vacuole — "Vacuole" alone is accepted. "Fluid sac" or "water store" score zero.

Y

cell wall — must say "cell wall," not just "wall" or "outer layer."

Z

nucleus — the structure that contains chromosomes and controls the cell's activities.

Examiner Alerts

Three errors flagged repeatedly across multiple series. Learn these now.

Alert 1 — Describing Instead of Naming

When the question says "name the structure," write the named term. Descriptions like "fluid sac" and "water store" describe the vacuole but do not name it — they score zero regardless of how accurate they are biologically.

Alert 2 — Bacterial Cell Wall = Cellulose

Never write this. Plant cell walls are made of cellulose. Bacterial cell walls use a different polymer. The spec does not require you to name it — but you must never use "cellulose" for bacteria.

Alert 3 — DNA vs Chromosome vs Gene

These three terms are NOT interchangeable. DNA is the molecule. A chromosome is a long coiled strand of DNA (found in eukaryotic nuclei). A gene is a section of a chromosome that codes for a specific protein. Mark schemes are strict — use the correct level of term for the question asked. For bacteria: write "single loop of DNA" not "chromosome" — bacterial DNA is not packaged into chromosomes.

Common Errors

Pause and screenshot. The most frequent mark-losing errors on this topic across 12 papers.

✗ Wrong

"plants don't have mitochondria" / "only animal cells respire"

✓ Correct

Plants do have mitochondria — they photosynthesize AND respire continuously

✗ Wrong

"fluid sac" or "water store" for the large plant cell space

✓ Correct

"(permanent) vacuole" — the named term only

✗ Wrong

"powerhouse of the cell" for mitochondria

✓ Correct

"mitochondria — site of aerobic respiration; releases energy"

✗ Wrong

"bacterial cell wall is made of cellulose"

✓ Correct

"bacterial cell wall — different polymer, NOT cellulose"

✗ Wrong

"bacteria have a nucleus" or "bacteria have a small nucleus"

✓ Correct

"bacteria have no nucleus — DNA is a single loop in the cytoplasm"

Three Things to Remember

Three takeaways. You're set for any cell-identification question on Paper 1.

1. Eukaryotic vs Prokaryotic

Eukaryotic cells (animal, plant, algal, fungal) have a nucleus. Prokaryotic cells (bacteria) have no nucleus — DNA is in a single loop in the cytoplasm, plus possible plasmids.

2. The Structure Lists

Animal: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes. Plant: those 5 plus cell wall (cellulose), permanent vacuole, chloroplasts. Bacteria: cell wall (not cellulose), membrane, cytoplasm, DNA loop, plasmids, ribosomes.

3. Mark-Scheme Wording Matters

Write "permanent vacuole" not "fluid sac." Write "releases energy" not "produces energy." Write "single loop of DNA" not "circular chromosome" for bacteria. Use the AQA term — not a description.

Summary

Three Cell Types — Key Differences

Animal cells: eukaryotic · nucleus · no cell wall · no chloroplasts · no permanent vacuole

Plant cells: eukaryotic · nucleus · cellulose cell wall · permanent vacuole · chloroplasts (green parts)

Bacterial cells: prokaryotic · no nucleus · DNA loop + plasmids · cell wall (not cellulose) · no mitochondria

Algal cells: treated same as plant cells by AQA — chloroplasts, cell wall, permanent vacuole

Wording to Memorise

"(permanent) vacuole" — not "fluid sac" or "water store"

"releases energy" — not "produces / makes / creates energy"

"single loop of DNA" — not "circular chromosome" for bacteria

"different polymer" for bacterial cell wall — not "cellulose"

Next Lesson

Lesson 1.02 — Specialised Cells. Sperm, nerve, muscle, root hair, xylem, phloem — how each cell's structure is adapted to its function. The feature-function link is the mark.