Chapter 10b Flashcards
protective carrier
the thing that transports dna or rna
often made of protein
there is no cellular activty inside the carrier
viruses
simply carriers of genetic material
their only job is to reproduce
nonliving obligate parasites
have togo into a cell to replicate and cannot reproduceoutside of cells
Many viruses are species specific meaning they bind to particular “docking” site on cells
viruses with membranes
some viruses have a membrane enclsing dna or rna - most viruses that infect humans have membranes since our cells have membraces
how do viruses cause infection?
cannot reproduce on their own; must enter a cell and use the cell’s enzymes and ribosomes to make more viruses
viral replication types
lytic cycle
lysogenic cycle
budding
lytic cycle
tkaes over the cell and makes mutliple copies; lyses the cell and releases all viruses at once by breaking open the cell
viruses make copies of itself and destroys the cell
(1. injects dna into cell 2. takes over normal cell functions to make copies of itself 3. assembles new viruses 4. lyses the cell; breaks it open to release new virus at once
lysogenic cycle
inserts its dna in the dna of cell for a period of time; can go on to lytic cycle
inserts viral DNA in host’s dna and can remain there for a periodof time; viral dna is replicated when bacteria replicates; at some pointthe viral dna can come out which it then moves into the lytic cycle
budding
takes over cell and makes copies; new viruses bud off the cell individually (cell continues to be a virus factory)
- viral membrane fuses to membrane allow rna or dna to enter cell
- rna uncoated
- viral rna is sythesized
- viral proteins made
- more rna made
- parts assembled
- new virus”buds” off cell individually using some of cells membrane for its membrane
AIDS
acquired immune deficiency syndrome
HIV
human immunodeficiency virus
rna virus that uses revers transcriptase
reverse transcriptase (RT)
an enzyme that reverses the transcription process, making dna from rna instead of (dna>mrna>protein) HIV uses RT to (rna>Dna>mran>protein)
retrovirus
name of HIV because it goes backward
how HIV infects a cell
HIV binds to and fuses to cell membranes
(1. reverse transcriptase makes HIVdna from HIVrna 2. double stranded HIVdna is made 3. HIVdna is inserted into person’s dna and stays there 4. if HIV expresses itseld, HIVrna is made from HIVdna 5. HIVrna carries code to make and assemble HIVdna 6. HIV buds off cell)
why is HIV so dangerous
- it attacks the white blood cells that protect us against viruses (Helper T cell that directs the immune attack)
- it can hide in the host cell’s dna for years undetected
- it mutates rapidly - even within an individual, so it can evade the immune system and become resistant to medicines
drug therapies for HIV
nucleotide analogues
reverse transcriptase inhibitors
protease inhibitor
nucleotide analogues
adapted nucleotides that block reverse transcriptase from working
ex: AZT
side effects of nucleotide analogues
healthy cells also take up AZT by mistake, preventing them fro dividing
reverse transcriptase inhibitors
stops HIV enzyme RT from functioning (so no HIVdna is made)
we don’t havethe RT enzyme so these drugs do not effect us, little or no side effects
protease inhibitor
prevens the HIV enzyme Protease from functinoing
viral cells treated with protease inhibitors “produce defective HIV, lacking infectious viral core”
problems with treatments for HIV
HIV mutates rapidly (have to change medications regularly, most people have gone through most or all of the medications used to treat HIV)
drug cocktails (most people take 3-4 drugs together to attack the virus in a number of ways, expensive, toxic, 10-15 pills a day for the rest of your life)
still a very dangerous virus (we can treat hiv, but we are far from curing it)
avoid it (passes through body fluids (blood, semen, vaginal fluid, breast milk)
