VIRUSES

Question 1

What are viruses?

Answer 1

-Lack cytoplasm and are not cells
-Only able to reproduce inside living cells, thus are parasites
-A protein coat called a capsid surrounds the nucleic acid core and the virus’ DNA or RNA contains the code for making new proteins in it’s capsid :. new viruses.
-Each type opf virus will only recognise and infect certain types of cell thus they are highly specific to their hosts

Question 2

Bacteriophage

Answer 2

-Any one of a number of viruses that infect bacteria
-Consist of a core of DNA surrounded by an outer protein coat

Question 3

How do bacteriophages enter a host cell?

Answer 3

-Bacteriophages attach to specific receptors on the surface of the bacteria (specififity means that they can only infect bacteria with the receptors they can bind to)
-Complex bacteriophages use a syringe like motion to inject their genetic material into the cell
-After making contact with the appropraite receptor, the tail fibres bring the base plate closer to the surface of the cell
-Once attached completely, the tail contracts, injecting genetic material through the bacterial membrane

Question 4

Release of new bacteriophages

Answer 4

-The new phages are released by cell lysis
-Many hundred phages can be created in a small amount of time in the cell, therefore this causes the bacterial host cell to ‘burst’ and the phages to be released via lysis

Question 5

HIV defintion

Answer 5

Human Immunodeficiency Virus

Question 6

Structure of HIV

Answer 6

-Belongs to a group of viruses containing RNA called retroviruses (because they can convert their RNA back into a viral DNA copy using reverse transcriptase)
-HIV is made up of a core of RNA bounded by a protien coat and a lipid bilayer containing glycoproteins
-HIV invades a type of lymphocyte called a helper T-cell and so may weaken the immune system thereby causing AIDS (acquired immune deficiency syndrome)