Microbio Ch 6

Microbiology Chapter 6 - an introduction to viruses and prions

each capsid is made of identical subunits called _____, made of _____

capsomers, proteins

What type is the specialized capsid only with bacteriophages?

complex

_____ is a state in which a bacteriophage (virus that infects bacteria) becomes dormant within the host bacterium without immediately killing it

Lysogeny

1. have a specific receptor on its surface for viral attachment, and 2. has to contain all of the enzymes and materials needed to produce new virions =

what a cell must have for a virus to infect it

_____ is for phage, _____ for animal viruses

lysogeny, latency

animal viruses cannot _____

inject their DNA

_____ virus replication is more complex than _____ replication because host cells are more complex

animal, phage

RNA viruses compared to DNA are _____ and _____

unstable, sensitive

What are the 3 media used to grow viruses?

live animal tissues, bird embryos, human cells and culture

what is the size range of viruses?

0.02-0.3 nanometres

What do viruses possess that allows adhesion to cells?

glycoprotien spikes

What are the two cycles viruses can go through (both animal and phage)

Lytic and Lysogenic

1. the viral genome directs the cell to manufacture new capsid proteins and replicate the viral genome, 2. new viruses are assembled inside the cell, 3. the new viruses either bud from the cell surface or erupt en masse from the cell, killing the host cell

the lytic cycle

1. viral genome is inserted into host genome (prophage/ provirus), 2. the viral genome remains in a latent state or lysogeny without causing disease, 3. each time the cell replicates, the viral genome is copied, 4. stressor = viral genome is activated and proceeds to direct the production of new viruses entering the lytic cycle

the Lysogenic Cycle

initial response by monocytes and lymphocytes, inflammation at site of viral entry, followed by antibody production =

immune response to viruses

immune response to viruses includes initial response by _____ and _____, ______ at site of viral entry, followed by _____ production.

monocytes, lymphocytes, inflammation, antibody

A fully formed extracellular particle that is virulent is a =

virion

Some animal viruses remain _____ and bacteriophages remain _____, where they do not enter the lytic stage and lyse cells

latent, lysogenic

When growing viruses on tissue, you detect them when you see _____

plaques

Why are viral infections hard to treat?

drugs that attack viral replication have serious side effects

the protein shell enclosing the viral genome; may be rod-shaped, polyhedral, or more complex in shape; made from protein subunits (capsomeres)

Capsid

a membrane, derived from membranes of the host cell, that cloaks the capsid; vesicles can leave (exocytosis)

Viral Envelope

20-sided capsid with 12 corners is described as =

Icosahedral

Complex viruses: atypical viruses examples =

Poxviruses and bacteriophages

Either DNA or RNA, never both; carries necessary genes needed to invade host cells and redirect cell's activity to make new viruses

Viral genome

Nucleic Acid molecules (DNA OR RNA) and Matrix Proteins enzymes (not found in all viruses), describes =

Central core of a virus

-range from 2300 to 31,000 bases

-generally have fewer genes

-more fragile than double stranded nucleic acids

ssRNA genomes

an enzyme that brings about the formation of a particular polymer, especially DNA or RNA.

polyamerase

An enzyme encoded by some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis.

reverse transcriptase

"Long COVID": ongoing, relapsing, or new symptoms or conditions present 30 or more days after COVID infection

post-acute sequelae of covid

transmission of SARS-CoV-2

respiratory droplets

small, noncellular particles with a definite shape, size, and chemical composition =

virus

viruses can infect which cell types?

any

viruses are considered the most _____ microbes on earth

abundant

viruses are _____ _____ parasites

obligate intracellular

are viruses living organisms?

no

the structure of a virus includes =

genetic material and protein

viruses lack _____ ____ machinery

protein synthesizing

viruses only contain the parts needed to _____ and _____ a host cell

invade, control

all viruses have _____, protein coats that enclose and protect their nucleic acid

capsids

protein coats that enclose and protect a viruses nucleic acid

capsids

a capsid together with the nucleic acid is the _____

nucleocapsid

some viruses have an external covering called an _____ made from the _____ _____

envelope, phospholipid bilayer

viruses lacking an envelope are termed =

naked

the two structures of a viral capsid are =

helical, icosahedral

a viral capsid that is _____ is described as a continuous helix of capsomers forming a cylindrical nucleocapsid

helical

mostly animal viruses contain a _____ _____

viral envelope

exposed proteins on the surface of a viral envelope are called _____

spikes

viral spikes are essential for ______

attachment to host cell

complex viruses are _____ viruses

atypical

______ viruses are atypical viruses

complex

_____ lack a typical capsid and are covered by a dense layer of lipoproteins

poxviruses

_____ are proteins attached to fats/lipid molecule

lipoproteins

some _____ have a polyhedral nucleocapsid along with a helical tail and attachment fibers

bacteriophages

either DNA or RNA based but never both =

viral genome

the two types of viral genome

DNA or RNA

type of viral genome that is usually double stranded (ds) but may be single stranded (ss), can be circular or linear

DNA

type of viral genome that is usually single stranded (ss) but may be double stranded (ds), may be segmented into separate ____ pieces

RNA

ssRNA genomes ready for immediate translation are termed =

positive-sense RNA

ssRNA genomes that must be converted into proper form are termed =

negative-sense RNA

viral enzyme that deals with DNA or RNA

polymerase

viral enzyme that copies RNA

replicases

viral enzyme that deals with synthesis of DNA from RNA

reverse transcriptase

the phases in the animal virus multiplication cycle =

absorption, penetration, uncoating, synthesis, assembly, release

phase of the animal virus multiplication cycle characterized by the binding of virus to specific molecules on the host celll

absorption

the phase of the animal virus multiplication cycle characterized by genome enters the host cell

penetration

the phase of the animal virus multiplication cycle characterized by the viral nucleic acid is released from the capsid (only in animal viruses)

uncoating

the phase of the animal virus multiplication cycle characterized by viral componenets are produced

synthesis

the phase of the animal virus multiplication cycle characterized by assembled viruses are relased by budding (exocytosis) or cell lysis

release

the spectrum of cells a virus can infect is called =

host range

hepatitis B infects which kinds of cells

human liver

poliovirus infects which type of cells

primate intestinal and nerve cells

rabies infects which type of cells

various cells in many mammals

during penetration, the flexible cell membrane is penetrated by the whole virus or its nucleic acid by _____ or _____

endocytosis, fusion

process in which the entire virus is engulfed and enclosed in a vacuole or vesicle

endocytosis

process in which the viral envelope merges directly with the host cell membrane resulting in the nucleocapsids direct entry into the cytoplasm

fusion

shedding of the viral envelope during uncoating happens in _____ cells only

animal

DNA viruses generally are replicated and assembled in the _____

nucleus

_____ viruses generally are replicated and assembled in the nucleus

DNA

RNA viruses generally are replicated and assembled in the _____

cytoplasm

_____ viruses generally are replicated and assembled in the cytoplasm

RNA

assembled viruses leave the host in two ways =

budding (exocytosis) or lysis

nucleocapsid binds to the host cell membrane which pinches off and sheds the viruses gradually; cell is not immediately destroyed

budding (exocytosis)

nonenveloped and complex viruses release when the host cell dies and ruptures

lysis

viruses are the most common cause of _____ _____

acute infections

virus-induced damage to cells is termed =

cytopathic effects

changes in size and shape, cells fusing together, cell lysis, altered DNA, and transformation of cells into cancerous cells are examples of viral _____ _____

cytopathic effects

when cells harbor the virus and are not immediately lysed =

persistent infections

infection can last weeks or a hosts lifetime, several can periodically reactivate =

chronic latent state

virus that may remain hidden in brain cells for many years

measles

virus characterized by cold sores and genital sores

herpes simplex

virus causing chickenpox and shingles

herpes zoster

SARS-CoV-2 virus causes what condition

COVID-19

term for vaccine effectiveness determined by measuring vaccinated vs unvaccinated

absolute effectiveness

term for vaccine effectiveness determined by comparing vaccine types or regimen

relative vaccine effectiveness

term for vaccine effectiveness determined by comparing the number of doses

incremental vaccine effectiveness

mode of transmission for influenza

aerosol droplets

someone with influenza is the most infectious in the first _____ days after symtpoms develop

3-4

population at risk for influenza is =

everyone