microbio lec chapter 13 acellular organisms

3 main parts of a virus

protein coat

envelope (some)

nucleic acid

viruses always require a

host

describe host range

spectrum of host cells that a virus can multiply in

what are host ranges limited by for a virus

structural compatibility, biochemical requirements for replication, and host immune defenses

host ranges are determined by

specific attachment sites/receptors on host cells and availability of certain host cell factors

viruses are on a ___ scale (size)

nanometer ; 10^-9

what must be used to observe a virus

electron microscopy

describe protein coat

capsid ; surrounds the virus

describe nucleic acid

DNA or RNA (never both)

single or double stranded

linear/circular

describe envelope

lipids, proteins, carbohydrates, glycoproteins

glycoproteins are the what on enveloped viruses

spikes

different morphologies for viruses

helical

polyhedral

pleomorphic

complex

describe helical

hollow cylinder ; TMV

what is TMV

tobacco mosaic virus

describe polyhedral

many sides

what is icosa hedral

20 sides ; HPV

describe HPV

human papillovirus

describe pleomorphic

nonspecific shape, enveloped viruses, roughly spherical

describe complex

complex structure, bacteriophages

what is the shape bacteriophages

polyhedral capsid with helical tail

viruses must be grown on

living cells

how are animal viruses grown

use of embryonated eggs / cell/tissue culture

how are bacterial viruses grown

bacterial plate with bacterial cells

2 types of bacteriophage multiplication

lytic and lysogenic cycle

what are the steps of a lytic cycle

attaches to surface of cell

injects/entry DNA into cell

goes through biosynthesis

assembly/mature into phages

release through lysis

what are the steps of lysogenic cycle

attachment to cell

entry into cell

injects DNA into cell’s chromosomes

host cell makes copies of its DNA and prophage

environmental trigger to release prophages into cytoplasm

lytic switch:

prophages assemble

prophages release through host cell lysis

example of lysogenic cycle

vibrio cholera

describe cholera disease

dysentery disease that causes digestive system to shut down and ability to absorb water is gone

cholera disease only produces toxin when it is

lysogenic

steps for animal virus

attachment to cell

entry

uncoat

synthesis of viral proteins

assembly

release

attachment depends on

cell surface and attachment type

types of entry for animal viruses

receptor mediated endocytosis and fusion

describe receptor mediated endocytosis

virus attaches to receptor and brought in through a vesicle

describe fusion

capsule brings in virus content

where is RNA virus uncoated in animal cells

cytoplasm

where is DNA virus uncoated in animal cells

nucleus

viral RNA goes where for translation

ribosomes

types of release for animal viruses

non-lytic and lytic

describe lytic

lyse cell

describe non-lytic

use exocytosis to exit

which type of virus use non-lytic the most

enveloped viruses

types of RNA viruses

+ strand

- strand

retroviruses

describe + strand

translated directly from mRNA

describe - strand

complement to mRNA

- strand being complimented undergoes what process

transcription

what enzyme completes the compliment

viral RNA polymerase

describe retroviruses

undergo reverse transcription (RNA —→ DNA)

what enzyme completes reverse transcription

reverse transcriptase

where is DNA inserted after reverse transcription

into host genome/chromosome

what is an example of retrovirus

HIV

describe prions

infected proteins

what do prions target

brain tissue ; leads to spongiform encephalopathy

describe spongiform encephalopathy

brain tissue has holes in it

prions are a result of

altered protein

PrP^c is the ___ protein

normal

PrP^sc is the ___ protein

altered

symptoms for prions happen

quickly

example of prions

mad cow disease