A-Level Biology AQA Notes
3.2.1.2 Structure of prokaryotic cells and viruses
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Prokaryotic Cells
- Prokaryotes are smaller and simpler than eukaryotes
Feature | Eukaryotic Cell | Prokaryotic Cell |
Nucleus | Present | Absent |
DNA | Linear and packaged into chromosomes in nucleus | Circular and freely floating in cytoplasm |
Cell Membrane | Present | Present |
Membrane-bound Organelles | Present | Absent |
Ribosomes | Present (80S) | Present (70S) |
Cell Wall | Sometimes (Celloulose or chitin) | Present (peptidoglycan) |
Chloroplasts | Sometimes | Absent |
Flagellum | Absent | Sometimes |
Capsule | Absent | Sometimes |
Plasmid | Absent | Sometimes |
- Bacteria replicate by binary fission
Viruses
- Viruses are acellular and non-living.
- The basic structure of viruses is:
- Viruses replicate by binding to the host cell, injecting their genetic material into the cell, using the host’s machinery to replicate & burst out of the host cell.
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