Viruses Flashcards
(21 cards)
What are viruses measured in?
nanometers (nm) as they are very small
What 2 structures do all viruses have?
All viruses have a protein coat (capsid) that surrounds a nucleic acid. Viruses can have DNA or RNA
Give an example of a virus with DNA as it’s nucleic acid
Bacteriophage
Give an example of a virus with RNA as it’s nucleic acid
HIV (Human Immunodeficiency Virus)
What is HIV comprised of? (It’s structure)
HIV viruses have an RNA core, surrounded by a protein capsid.
There is a lipid bilayer containing glycoprotein that surrounds the virus.
Within the core there is also RNA Transcriptase
Describe the additional layer that surrounds the protein coat in HIV
A phospholipid bilayer (obtained from the human cell). Glycoproteins are present in this layer too
What is the role of RNA reverse transcriptase?
The reverse transcriptase catalyses the synthesis of DNA from viral RNA
What does the newly synthesised DNA then do in the progression of HIV infection?
The DNA codes for new protein coats (capsids) and viral RNA to make new viruses
Why is HIV known as a retrovirus?
HIV contains RNA which is used as a template to make DNA
What type of cell does HIV invade?
Human lymphocytes called helper T-cells. These T-cells are important in the immune response
What is AIDS? How is it developed from HIV?
AIDS is a medical condition in which the immune system is critically compromised as a large amount of Helper T-cells are invaded by the HIV virus
The structure of a bacteriophage
The nucleic acid core is DNA which is surrounded by a protein head.
There is a contractile sheath also made from protein.
There is a base plate with tail fibres
What two structures of a bacteriophage are made of protein?
The protein head and the contractile sheath
What type of cell does a bacteriophage infect?
Bacterial cells
What does the DNA code for in a bacteriophage?
The production of new bacteriophage proteins
What is the role of the tail fibres?
The tail fibres attach to the bacterial cells
What is the progress of infection in a bacterial cell after it’s been infected by a bacteriophage?
The viral DNA synthesises new proteins heads (capsids).
The DNA will then replicate and package the new DNA into the new protein heads.
The bacterial cell is destroyed and will rupture to release the new viruses
Why are viruses not true cells?
Viruses contain no cytoplasm or organelles. Viruses are also inert unless they have access to a living cell
State 3 similarities between HIV and bacteriophages
- Very small
- Non-cellular
- Genetic material is within a capsid
State 5 differences between HIV and Bacteriophages
•They have different shapes. Phages have tail fibres attached to a base plate
• HIV protein coat is within a phospholipid bilayer
• Glycoproteins are present in HIV but not in phages
• Bacteriophages normally contain DNA while HIV contains RNA
• HIV contains reverse transcriptase
Why do most phages not contain reverse transcriptase
Most phages already have DNA which can replicate immediately
