Compare prokaryotic and eukaryotic cells
Compare cell organisation, DNA, ribosomes, size and organelles using the evidence supplied for each cell.
Section 1.2 · Cells as the basic units of living organisms
AS Level · Cambridge International Biology 9700, 2028–2030. Interpret only the structures supported by the provided image or description. Written practice is self-checked; it does not demonstrate practical microscopy competence.
Before you begin
- Recognise that organisms are made of cells and that a light microscope produces a magnified image.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Where is a typical bacterium’s circular DNA found?
What you will learn
- Compare a typical bacterial cell with typical plant and animal cells
- Use shared and distinguishing features in a structured comparison
Compare the same features in each cell
A typical bacterium is prokaryotic, unicellular and generally 1–5 µm in diameter. It has circular DNA not enclosed in a nucleus, 70S ribosomes, a peptidoglycan cell wall and no double-membraned organelles.
Typical plant and animal cells are eukaryotic and have a nucleus containing linear chromosomes. Their cytoplasm contains 80S ribosomes and membrane-bound organelles such as mitochondria. Typical plant cells also have a cellulose wall, chloroplasts in photosynthetic tissues and a large permanent vacuole.
State similarities as well as differences
All three cell types have a cell-surface membrane, cytoplasm, DNA and ribosomes. Use a named feature for each comparison rather than writing only “more complex”.
A comparison should specify both sides: for example, bacterial DNA is circular and not enclosed in a nucleus, whereas eukaryotic chromosomes are linear and enclosed within a nucleus. If a typical animal cell is compared with a typical plant cell, avoid presenting plant-specific structures as shared by both.
Pause and explain
Which feature is shared by bacterial, plant and animal cells?
Worked example
Compare a typical bacterium with a typical animal cell using DNA organisation, ribosomes and membrane-bound organelles.
Show the worked solution
- State both structures for each feature.
- Include a correct similarity or limitation if useful.
Answer A typical bacterium has circular DNA not enclosed in a nucleus, whereas a typical animal cell has linear chromosomes within a nucleus. Bacteria have 70S ribosomes, whereas eukaryotic cytoplasm has 80S ribosomes. A typical bacterium lacks double-membraned organelles such as mitochondria, while a typical animal cell contains mitochondria.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Compare a typical bacterium and an animal cell by three features.
Give me a hint
Use the same feature in each side of every comparison.
Compare my reasoning
- Bacteria are smaller and lack a nucleus.
- They differ in DNA organisation, ribosome type and double-membraned organelles.
A typical bacterium is generally 1–5 µm in diameter and an animal cell is typically larger. Bacterial circular DNA is not enclosed in a nucleus, whereas animal-cell linear chromosomes are nuclear. Bacteria have 70S ribosomes and lack double-membraned organelles; animal-cell cytoplasm has 80S ribosomes and contains mitochondria.
Look for these in your work
- Three paired comparisons
- Accurate size or organisation
State two similarities and two differences between a typical plant cell and a typical bacterium.
Give me a hint
Compare shared boundary/contents and wall or organelles.
Compare my reasoning
- Both have a cell-surface membrane and cytoplasm.
- Bacteria lack a nucleus and have peptidoglycan; plant cells have a nucleus and cellulose wall.
Both have a cell-surface membrane and cytoplasm. A typical bacterium has circular DNA not enclosed in a nucleus and a peptidoglycan wall; a typical plant cell has a nucleus with linear chromosomes and a cellulose wall, and may contain chloroplasts and a large permanent vacuole.
Look for these in your work
- Two similarities
- Two differences correctly paired
A comparison table says “both cells have 70S ribosomes.” Identify the error when one cell is a typical eukaryotic animal cell.
Give me a hint
Consider the ribosome location.
Compare my reasoning
- Bacterial cytoplasm has 70S ribosomes.
- Eukaryotic cytoplasm has 80S; 70S occurs in mitochondria and chloroplasts.
A typical bacterium has 70S ribosomes. A eukaryotic animal-cell cytoplasm has 80S ribosomes. Eukaryotic mitochondria have 70S ribosomes, but that does not make cytoplasmic ribosomes 70S.
Look for these in your work
- Bacterial type
- Eukaryotic location distinction
Common mistakes
- Using “prokaryotes have no DNA”
- Claiming eukaryotic cells lack 70S ribosomes in organelles
- Comparing two different features rather than the same feature
What can you explain now?
Where is a typical bacterium’s circular DNA found?
Compare with the explanation
Not enclosed in a nucleus
Prokaryotic DNA is not enclosed by a nuclear envelope.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Which features are shared by all cells, and which distinguish prokaryotes from eukaryotes?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.