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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
The key difference
Eukaryotic cells (plants, animals, fungi) have a membrane-bound nucleus and organelles like mitochondria. Prokaryotic cells (bacteria) have no true nucleus: their DNA is a single circular chromosome free in the cytoplasm.
All living organisms are made of cells, but cells come in two fundamentally different types. Prokaryotic cells are simpler, smaller, and lack membrane-bound organelles. Eukaryotic cells are more complex, larger, and contain compartmentalised organelles. This distinction is tested in Topic 2 of the IGCSE Biology syllabus.
Feature
Prokaryotic Cells
Eukaryotic Cells
Nucleus
No true nucleus: DNA free in cytoplasm (nucleoid region)
The defining difference between prokaryotic and eukaryotic cells is the nucleus. In eukaryotes, the nucleus is surrounded by a double membrane (nuclear envelope) that separates the genetic material from the cytoplasm. This allows eukaryotic cells to regulate gene expression more precisely. In prokaryotes, the DNA floats freely in the cytoplasm with no membrane barrier, giving direct access for transcription but less regulation.
Plasmids and Antibiotic Resistance
Prokaryotic cells (bacteria) often contain small extra circles of DNA called plasmids in addition to their main circular chromosome. Plasmids can carry genes for antibiotic resistance and can be transferred between bacteria through a process called conjugation. This is one mechanism by which antibiotic resistance spreads through bacterial populations: and why it is a major public health concern.
Plasmids are also used in genetic engineering as vectors to carry desired genes into bacterial cells for producing useful proteins (e.g. Human insulin).
Try a comparison question (3 marks)
State three differences between a bacterial cell and an animal cell. [3]
Show the answer and marking guidance
Bacterial cells have no true nucleus / DNA is free in the cytoplasm; animal cells have a membrane-bound nucleus
Bacterial cells have a cell wall made of peptidoglycan; animal cells have no cell wall
Bacterial cells have no membrane-bound organelles (e.g. No mitochondria); animal cells have mitochondria and other membrane-bound organelles
Original Cambridge-style practice written for this site.
Common comparison mistakes
When answering a compare question, write matched pairs rather than two separate descriptions.
Saying bacteria have "no DNA": they do have DNA, it is just not enclosed in a nucleus
Confusing bacterial cell walls (peptidoglycan) with plant cell walls (cellulose): they are different materials
Saying eukaryotic cells are "always bigger": while generally true, some eukaryotic cells (e.g. Red blood cells ~7 μm) are smaller than some bacteria
Forgetting that both cell types have ribosomes: prokaryotic ribosomes are just smaller