Bacteria and Prokaryotic Cells

IGCSE Edexcel Biology
1.3 Prokaryotic Organisms (Bacteria)
Key Concept: Prokaryotes are single-celled organisms without a nucleus and with circular DNA and plasmids.

Section A: Structure

1. List five features of a typical bacterial cell. [5]
2. Label the diagram with: cell wall, cell membrane, cytoplasm, circular DNA, plasmid. [5]
[Bacterial cell diagram]

Section B: Comparison

3. State three differences between prokaryotic and eukaryotic cells. [3]

Section C: Examples and Roles

4. Give one example of a useful bacterium and one example of a harmful bacterium. [2]
5. Explain two ways bacteria can be useful and two ways they can be harmful. [4]
Total marks: 19

Mark Scheme

1. Any five: cell wall, cell membrane, cytoplasm, circular DNA, plasmids, ribosomes (accept any five) [5]
2. Correct labels for all five structures [5]
3. Any three: no nucleus, circular DNA, plasmids, smaller size, no membrane-bound organelles (any three) [3]
4. Useful: Lactobacillus bulgaricus for yoghurt; Harmful: Pneumococcus causes pneumonia (accept any correct examples) [2]
5. Useful: food production, decomposition, nitrogen fixation; Harmful: disease, food spoilage, toxins (any four) [4]