HIV

5.7 - Describe the structure of HIV

* Lipid envelope + attachment proteins embedded



* inside the envelope, Capsid encloses two single RNA strands + enzymes including reverse transcriptase(it is called this because it catalyses the production of DNA from rna )

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* It's a retrovirus as it contains RNA

Explain the process by which HIV replicates (7)

1. HIV Enters bloodstream + circulates
2. Protein on HIV binds to CD4 protein receptors (normally on T-Helper cells)
3. The protein capsid fuses with cell surface membrane. RNA + enzymes of HIV enter the helper t cell.
4. HIV Reverse transcriptase converts RNA → DNA
5. DNA is moved into helper t cells nucleus and inserted into host DNA.
6. DNA transcribed into mRNA, which uses ribosomes to make viral proteins.

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7)mRNA passes out of the nucleus through a nuclear pore and uses the cells’ protein synthesis mechanisms to make HIV particles.

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8) HIV particles leaves helper t cell , using part of cell’s CSM to from lipid envelope.

How does HIV infect a host?

Infects and kills helper T-cells (the host cells)
Their role in the immune response is stopped
AIDS occurs when the number of helper T-cells in the body reaches a low level

What organelles does the HIV require form the host T-helper cell and why?

Needs the enzymes and ribosomes to enable it to reproduce

How does HIV lead to the development of AID’s?

Attacks helper T cells

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\-t cells are important in cell mediated immunity.without a sufficient number of t cells, the immune system cannot stimulate the b cells to produce antibodies or the cytotoxic t cell.

Memory cells may also become infected and destroyed

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infects immune system, so sufferers cannot respond effectively to other pathogens secondary diseases ultimately cause deaths.

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Recall 2 ways to diagnose AIDs. MS [2]

check for AIDs-related symptoms
Number of Th cells

5.7 - Explain why antibiotics are ineffective against viral disease

Antibiotics work by preventing bacteria making normal cell walls; causing them to burst when water enters via osmosis
Viruses rely on host cells for metabolic activities; no metabolic pathways for antibodies to disrupt
Viruses have a protein coat so do not have sites where antibiotics can work

What does AIDs stand for?

acquired immunodeficiency syndrome

What is AIDS?

The immune system deteriorates and eventually fails
Those with AIDS are vulnerable to other infections such as pneumonia