A-LEVEL NOTES
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A-LEVEL NOTES

A-LEVEL BIOLOGY AQA NOTES 
structure of prokaryotic cells & 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
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​Viruses
  • Viruses are acellular and non-living.
  • ​The basic structure of viruses is:
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  • ​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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