A-Level Biology Specification

AQA 7402

Section 2.1.2: Structure of prokaryotic cells and of viruses

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#2.1.2.1

Prokaryotic cells are much smaller than eukaryotic cells. They also differ from eukaryotic cells in having:

- cytoplasm that lacks membrane-bound organelles
- smaller ribosomes
- no nucleus; instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins
- a cell wall that contains murein, a glycoprotein.

#2.1.2.2

In addition, many prokaryotic cells have:

- one or more plasmids
- a capsule surrounding the cell
- one or more flagella.

Details of these structural differences are not required.

#2.1.2.3

Viruses are acellular and non-living. The structure of virus particles to include genetic material, capsid and attachment protein.