Prokaryotic Cells and Viruses

The Edexcel A-Level Biology specification (9BI0) requires a thorough understanding of prokaryotic cell structure and how it differs from eukaryotic cells. You must also understand the structure of viruses and the debate surrounding whether they can be classified as living organisms. This lesson covers all the key content for Topic 2.

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What Is a Prokaryotic Cell?

Prokaryotic cells are cells that lack a true nucleus — their genetic material is not enclosed within a nuclear envelope. The term "prokaryote" comes from the Greek pro (before) and karyon (kernel/nucleus). Prokaryotes include the domains Bacteria and Archaea.

Prokaryotic cells are typically much smaller than eukaryotic cells, usually in the range of 0.2–5.0 $\mu m$μm in diameter, compared to 10–100 $\mu m$μm for most eukaryotic cells.

Exam Tip: The specification requires you to understand the structural features of prokaryotic cells and be able to compare them with eukaryotic cells. A comparison table is almost always the best way to present this in an exam answer.

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Structure of a Prokaryotic Cell

Cell Wall