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SCIPAD - BIG IDEAS - BOOK 2
LIFE OF MICROBES
Viral Reproduction
Viruses require a host cell in order to reproduce. They cannot perform the chemical processes
needed to reproduce, and rely on the host cell's processes to multiply. The host cell is usually
destroyed at the end of this process. Viral infections are always harmful to the host.
Viral reproduction can be broken down into five basic steps:
Adsorption Penetration Synthesis Maturation Release
Attachment/Adsorption
Spike proteins on the surface of the virus
bind with the outside of the host cell
allowing her virus to attach itself to the
Penetration
The virus releases its genetic
material (DNA or RNA) into the host
Synthesis
The genetic material of the virus instruct
the cell to make components of the virus.
Maturation
The various viral proteins and nucleic
acids are assembled into new virus
Release
Once the viruses have used all the host cell’s
resources, the newly formed viruses are
released and the host cell dies. The new virus
particles are now free to infect new host cells.
Viral Reproductive Cycle of a T4 Bacteriophage
Bacteriophages (from ‘bacteria’ and the Greek word ‘phagein’ meaning “to devour”) are
viruses that infect bacteria. They are one of the most common types of virus on Earth.
1. Complete the table by briefly summarising the stages of viral reproduction.
Order Name of Stage Summary of processes
1
2 Penetration
3
4 New viruses are assembled.
5
2. State why all viral infections are considered harmful. 

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