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Tutorials » Cell Biology » Biological Viruses

Biological Viruses
- Cell Biology

The prime directive of all organisms is to reproduce and survive, which is also the case for viruses, which in most cases are considered a nuisance to humans.

Viruses - An Overview

Viruses possess both living and non-living characteristics. The unique characteristic that differentiates viruses from other organisms is the fact that they require other organisms to host themselves in order to survive, hence they are deemed obligate parasites.

Viruses can be spread in the following exemplar ways

  • Airborne - Viruses that infect their hosts from the open air
  • Blood Borne - Transmission of the virus between organisms when infected blood enters an organisms circulatory system
  • Contamination - Caused from the consumption of materials by organisms such as water and food which have viruses within

Therefore viruses have many means of getting transmitted from one organism to another.

Cell Assimilation by a Virus

Viruses are tiny micro-organisms, and due to their size and simplicity, they are unable to replicate independently. Therefore, when a virus is situated in a host, it requires the means to reproduce before it dies out without producing more viruses.

This is done by altering the genetic make up of a cell to start coding for materials required to make more viruses. By altering the cell instructions, more viruses can be produced which in turn, can affect more cells and continue their existence as a species.

The following is a step by step guide of how an example bacteriophage (a virus that infects bacteria) takes control of its host cell and reproduces itself.

  • The virus approaches the bacteria and attaches itself to the cell membrane
  • The tail gives the virus the means to thrust its genetic information into the bacteria
  • Nucleotides from the host are 'stolen' in order for the virus to create copies of itself
  • The viral DNA alters the genetic coding of the host cell to create protein coats for the newly create viral DNA strands
  • The viral DNA enters its DNA coat
  • The cell is swollen with many copies of the original virus and bursts, allowing the viruses to attach themselves to other nearby cells
  • The process begins all over again with many more viruses attacking the hosts' cells

Without a means of defence, the host that is under attack from the virus would soon die. The next page looks at how organisms defend themselves from these ruthless viruses.


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