T2: Viruses Flashcards
what is the structure of viruses?
a nucleic acid core (their genomes are either DNA or RNA, and can be single or double-stranded)
a protein coat known as a ‘capsid’
some have a ‘envelope’ formed usually from the membrane phospholipids of a cell they were made in
how does HIV lead to AIDS?
weakens the immune system by infecting and destroying T helper cells, so B cells are no longer activated and antibodies aren’t produced
this leads to the development of AIDS
how do viruses replicate?
a virus uses attachment proteins on its surface to bind to complementary receptor proteins on the surface of a host cell
the virus then injects its DNA or RNA into the host cell
the host cell then uses its nucleic acid and ribosomes to
produce new viral particles
eventually, new viral particles are released through lysis or budding
the exiting of viruses damages their host cells, causing disease
why are viruses specific?
different viruses have different attachment proteins so can only bind to cell types with the complementary receptor proteins
how does HIV replicate (6)
1- HIV attaches to CD4 receptors on T helper cell and injects RNA and reverse transcriptase
2- Reverse transcriptase uses the viral RNA as a template to make a DNA copy inserted into the chromosome
3- The vial DNA is transcribed to viral mRNA and translated to viral proteins
4- Viral proteins and RNA form new HIV particles which burst out of the host cell to infect more T helper cells
5- This destroys the T helper cell, leading to a dramatic reduction in immune capability of the host
