Bacteria and viruses

Biology Unit 4
Revision Notes




Topic 6: Infection, Immunity and Forensics
8. Distinguish between the structure of bacteria
and viruses.
Bacteria Viruses
Cell surface membrane, cytoplasm, cell wall, No cell wall, cell surface membrane, cytoplasm
ribosomes, plasmids, and sometimes or organelles. Nucleic acid enclosed in protein
Mesosomes, flagellum and pili…

Biology Unit 4
Revision Notes



Retroviruses
Retroviruses (including HIV and Rous sarcoma) have a different and complex lifecycle. Their genetic
material is viral RNA.

1. The retrovirus attacks an animal cell
2. Viral RNA enters the host cell. This RNA cannot be used as mRNA
3. Viral RNA is translated…

Biology Unit 4
Revision Notes



Binary fission ­ once a bacterium reaches a certain size, the DNA is replicated and the old
cell wall begins to break down around the middle of the cell
In certain situations, some types of bacteria can reproduce using what appear to be different
forms…