akaryotes summary Flashcards
animal viruses
- envelope proteins
- envelope
- nucleocapsid
- viral genome (nucleic acid)
- tegument
envelope proteins
aid attachment to the host cell
envelope
derived from the host cell membrane
aids penetration of the host cell membrane
capsid
protective protein coat surrounding the nucleic acid.
built from capsomeres which are identical protein subunits
protects genetic material of the virus from attack by host cell enzymes
viral genome
DNA or RNA which codes for viral structural proteins and enzymes needed for replication.
tegument
the protein region between the nucleocapsid and the virion envelope
viral enzymes
retroviruses have reverse transcriptase to catalyse RNA into DNA.
bacteriophage
- protein coat
- head containing DNA
- collar
- sheath
- base plate
- tail fibres
viroids
naked pieces of circular RNA that do not have a capsid
interfere with transcription
satellites
nucleic acid surrounded by a capsid
require co-infection with a helper virus for replication to occur
prions
proteins only, do not have nucleic acid DNA or RNA
the trigger a conformational change in protein shape and are related to normal proteins
viruses reproduction
viruses are obligate intracellular parasites that need the host cells resources for reproduction
lysogenic cycle
a copy of the viral DNA is incorporated into the host DNA and remains dormant for a long time.
the viral DNA can be activated when external stressors occur, it can then enter the lytic cycle to produce new virions.
lytic cycle: general
attachment
penetration
biosynthesis
maturation
release
attachment
lytic cycle: general
the virions attach to host cell surface
penetration
lytic cycle: general
virus/viral components enter the cell by either: injecting the genome releasing it from the capsid or the whole nucleocapsid enters the cell
biosynthesis
lytic cycle: general
copies of viral components are produced
maturation
lytic cycle: general
the viral genomes are packaged into assembled capsids creasting intact viral particles/ complete virions
release
lytic cycle: general
virions are released from the cell to infect new host cells, and the host cell lyses due to lysozyme
attachment
bacteriophage lytic cycle
phage attaches to complementary receptor sites on the host cell
lysozyme breaks down a portion of the cell wall
penetration
bacteriophage lytic cycle
phage DNA is inserted into the cytoplasm via the sheath
biosynthesis
bacteriophage lytic cycle
phage DNA hijacks the host genome to produce replicate copies of themselves
maturation
bacteriophage lytic cycle
fragments of phage DNA and capsids are assembled into complete virions
release
bacteriophage lytic cycle
lysozyme breaks down the cell wall causing cell lysis and complete virions are released.
burst time = 50-200 new phages every 20-40 minutes.
attachment
animal virus lytic cycle
attachment sites on animal viruses unite with complementary receptor sites on the hosts cell membrane
attachment sites are distributed over the entire surface of the capsid.
penetration
animal virus lytic cycle
animal viruses are takin into the host cell complete where they then undergo uncoating in the cytoplasm.
biosynthesis
animal virus lytic cycle
the virus provides the information for the enzymes to make the virus components
maturation
animal virus lytic cycle
virus components are assembled into complete virions
release
animal virus lytic cycle
complete virions are released from the cell following cell lysis by lysozyme
benefical effects of viruses
vaccinations
gene therapy
bacteriophage therapy
vaccines
production of vaccines occurs through genetic engineering to render viral DNA harmless or to remove viral proteins. the body is infected with a non-fatal virus causing an immune response within the body.
types of vaccines
live attenuated - a less pathogenic non-disease causing form of the virus
killed - the virus is no longer able to replicate in the host cell
subunit - only part of the virus with the required antigen is introduced to the host.
bacteriophage therapy
bacteriophages are designed to infect specific bacterial infections causing bacterial cell lysis. e.g. used against antibiotic resistant pseudomonas Aeruginosa
gene therapy (viruses)
viruses are used in molecular biology as vectors - they are engineered to introduce DNA into a host.
detrimental effects of viruses
the flu, measles, cold sores
tobacco plant necrosis, spindle potatoes
the flu
caused by influenza A
transmitted by inhalation of air droplets containing influenza virus through sneezing or coughing.
measles
caused by measles virus
transmitted through inhalation of measles virus
cold sores
caused by the herpes simplex virus
transmitted through contact with herpes simplex virus
tobacco plant necrosis
causes tobacco plant death by tobacco mosaic virus which leads to economic damage due to loss of production
spindle potatoes
causes potato plant death by potato spindle which leads to economic damage due to loss of production.
detrimental effects of sub-viral particles
mad cow disease - prion
scrapie - prion
hepatitis D - viroid and satellite
