HIV and viral structure Flashcards
(14 cards)
what are viruses categorised as?
acellular (contain no cells and cellular structures) and non-living
what do viruses contain and where do they replicate?
contain nucleic acid core with DNA or RNA as genetic materials but replicates inside host cells because…
-no ribosomes so can’t synthesise proteins
-no mitochondria so no ATP
what is the nucleic acid core of viruses enclosed in?
capsid which is a protein layer that encloses and protects nucleic acid core, and enzymes
what do attachment proteins (on lipid envelope for HIV or on capsid for others) do?
helps virus identify/ attach to host cells so that DNA/ RNA can enter the cell
what does the viral lipid envelope on HIV do?
-helps protect virus from host’s immune system
-site of attachment proteins
-fuses with cell membrane to allow virus to enter host cell
what are the two enzymes in HIV?
reverse transcriptase and integrase
what does reverse transcriptase do in HIV?
catalyses the production of DNA from RNA
what type of cells do HIV cells replicate in?
helper T-cells called CD4 cells
at the start of HIV replication, where does the HIV virus attach?
to a receptor molecule on the cell membrane of the cell because the HIV virus has an attachment protein on its surface that has a complementary shape to the receptor
what happens once the HIV virus has attached to the membrane of the host cell?
the capsid of the HIV virus is released into the cell where the protein capsid is removed and the RNA is released along with the enzymes
reverse transcriptase is used to make a DNA copy of the RNA
once a DNA copy has been made, what happens?
the DNA is made to be double stranded and the integrase enzyme enables the DNA copy to be inserted into the human DNA
transcription of the viral genes occurs
describe how transcription of the viral gene occurs after the DNA copy is inserted into the human DNA?
the RNA polymerase within the cell and the free nucleotides of the cell are used to make mRNA
then the mRNA to the ribosome and translation occurs- specific tRNA molecules bring in specific amino acids in the correct order as their anticodons complementary base pair with codons on mRNA
how do amino acids in the sequence join during translation?
condensation reactions occur between the amino acids to form peptide bonds that join amino acids
viral proteins are produced and assembled into new virus capsids containing the viral enzymes
what happens as the virus leaves the cell once it has been replicated?
it removes part of the cell membrane to form the lipid envelope into which attachment proteins and antigens are inserted
the viruses go on to infect other cells
