2.1.6 Prokaryotic v Eukaryotic Cells

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Prokaryotic and eukaryotic cells are the two main types of cells in living organisms. They differ in structure, size, and complexity, with prokaryotic cells being simpler and smaller compared to eukaryotic cells.

Comparison of Prokaryotic and Eukaryotic Cells:

Feature	Prokaryotic Cells	Eukaryotic Cells
Size	Small (0.1–5 μm in diameter).	Larger (10–100 μm in diameter).
Nucleus	No true nucleus; DNA is free in the cytoplasm as a nucleoid.	True nucleus enclosed by a nuclear envelope.
DNA	Single, circular DNA molecule without proteins.	Linear DNA associated with histone proteins.
Organelles	No membrane-bound organelles.	Membrane-bound organelles (e.g., mitochondria, chloroplasts).
Ribosomes	Smaller (70S ribosomes).	Larger (80S ribosomes).
Cell Wall	Made of peptidoglycan (in bacteria).	Made of cellulose in plants or chitin in fungi. Animal cells lack a cell wall.
Reproduction	Binary fission (asexual).	Mitosis and meiosis (asexual and sexual).
Cytoskeleton	Very simple or absent.	Well-developed cytoskeleton for support and intracellular transport.
Flagella	Made of a single protein filament.	Made of microtubules arranged in a 9+2 structure.
Plasmids	Common (small circular DNA molecules).	Rare (found only in certain cell types).

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Key Points:

Prokaryotic Cells:

Found in bacteria and archaea.
Lack a nucleus and membrane-bound organelles.
Simpler structure suitable for unicellular organisms.

Eukaryotic Cells:

Found in plants, animals, fungi, and protists.
Contain a nucleus and a range of specialised organelles.
More complex and adapted for multicellular organisms.

Examples:

Prokaryotic: Bacteria (e.g., E. coli).
Eukaryotic: Plant cells (e.g., leaf cell), animal cells (e.g., nerve cell).

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Tip for Exams:

Use a comparison table for clarity in explaining differences.
Highlight unique features, such as the nucleoid in prokaryotes and membrane-bound organelles in eukaryotes.
Be prepared to give specific examples of each cell type.

Prokaryotic v Eukaryotic Cells Simplified Revision Notes for A-Level AQA Biology

2.1.6 Prokaryotic v Eukaryotic Cells

Comparison of Prokaryotic and Eukaryotic Cells:

Key Points:

Examples:

Tip for Exams:

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