intro to viruses pt 1

structure and polarity RNA dependent RNA polymerase

RNA _____ and _____ determine how viral mRNA is generated ad proteins are processed. RNA viruses must carry _____ to replicate

labile and transient cytoplasm RNA dependent RNA polymerase

RNA is _____ and _____. most RNA viruses replicate in the _____. host cell cannot replicate RNA, so the virus must encode for _____.

positive or negative sense

RNA viruses can be considered _____ and _____

labile -temperature, pH, proteases, detergents, drying -detergents can open the lipid membrane

enveloped viruses are considered _____ and are disrupted by _____ (5)

lipid bilayer stolen from the host

enveloped viruses contain nucleic acids and capsid proteins surrounded by a _____

glycoprotein lipoproteins

enveloped viruses have viral _____ or _____ in the envelope for host recognition and entry

attachment flexible and coiled

envelopes of viruses are studded with viral _____ proteins. the nucleocapsid inside the envelope is _____ and _____

sialic acid o epithelial cells for influenza A attachment and recognition (hemaglutinin binds to it)

example of cell surface macromolecules used for host viral receptors

5 protomers come together to make a pentamer (capsomere). 12 capsomeres come together to form a mature virion

explain the assembly of a icosahedral virion with 12 pentamers

3 sialic acid subtypes

the influenza A hemaglutinin spike is composed of _____ functional spike proteins. altering any of these proteins alters its recognition and infectivity. this glycoproteins binds to epithelial cell _____ for infectivity. they are important immunological targets for virus serotyping as the specific hemaglutinin sequence identifies the viral _____

nucleic acid fluid enzymes

there is _____, _____, and _____ inside the icosahedral

-animal virus (humans, birds) -bacteria viruses (phage) (more complicated structure)

2 different types of host cells and how do their structures differ

DNA or RNA

the genetic material, or nucleic acid, of nucleocapsids are _____ and _____

capsomere assembly

the _____ structure and _____ predict the shape of the icosahedral

-icosahedral: nucleic acid and enzymes housed within a closed capsid -helical: nucleic acid wrapped around and with structural and enzymatic proteins

2 different types of structural protein coats (capsid)

-intrinsic capsid structure or surface proteins: grooves -envelope: glycoprotein spikes

2 ways host cells recognize viruses (VAP)

-endocytosis for naked viruses and some enveloped viruses -membrane fusion of only enveloped viruses (because of lips envelope)

2 ways in which viruses can penetrate into the host cell for viral replication cycle

-structure -biochemical characteristics: structure and mode of replication

2 ways to primarily classify viruses based on taxonomy

single chain multimeric segmented

3 different structure of DNA or RNA in viruses

-virus has DNA or RNA -structural proteins -enzymes and nucleic acids to make binding proteins

3 things that add up to a nucleocapsid on a virus

-lytic: blowing up and killing the cell to leave. (always naked viruses) -budding: leave a few at a time in membrane allowing host cell to live (envelope viruses can leave this way) -exocytosis: exported in a vesicle so host cell lives

3 ways a virus can be released from a host cell

-must stay wet -spreads in large droplets, body fluids, and organ transplants -may survive the digestive system (but many do not) -does not need to kill cell to spread (can stay behind and cause reinfection)

4 consequences of enveloped viruses

-easily spread on fomites, hand to hand (because more resistant) -can dry out and retain infectivity -can survive the digestive system -can survive poor sewage treatment

4 consequences of naked capsids

-B-cell complement receptors (CD21): Epstein Barr virus -T-cell CDA: HIV (HIV binds to CD4) -ICAM-1 on epithelial cells for rhinoviruses (common cold) -the neural cell adhesion molecules (NCAM/CD56) neuron on acetylcholine receptors for rabies virus.

4 examples of viruses using host cell surface integral membrane proteins as their viral receptors

-disease presentation -means of transmission -host cell (host range) -tissue or organ targets (tropism)

4 ways to secondarily classify viruses

-recognition of target cell -attachment (adsorption): sticking to -penetration: breaking through -uncoating: unpacking and taking over (unpack virus in host cell) -macromolecular synthesis: making new (protein synthesis and genome replication) -assembly and release: packing up and moving out

6 steps to the viral infection cycle

stabile transient and labile

DNA is more _____ and is NOT _____ or _____ like RNA

encephalitis and hepatitis

Disease presentations: _____ and _____ are each caused by multiple types of viruses

protomer

_____ are the individual capsid protein unites that are intimately associated with the genome

complex

_____ capsids have multiple subunits with specialized shapes and functions. -ex: bacteriophages

helical

_____ is a capsid composed of nucleic acids bound to protomers (proteins) in a spiral with a hollow phase inside

capsid

_____ is the grouping of structural proteins that surround and encase the viral genome

caps-mere

_____ is the individual structural protein subunits of a capsid -like the individual protein panels of icosahedral

envelope

_____ is the lipid membrane surrounding the nucleocapsid

tropism epithelium (nasopharyngeal, respiratory, intestinal)

_____ is the target organ or tissue a virus is infecting. viruses are only infectious for certain cells and a vast majority of viruses enter through _____

genome positive negative

_____ structure of RNA viruses determines the mechanism of transcription and replication. _____ RNA viruses act as mRNA and translate immediately. _____ RNA viruses must be copied to mRNA first

genome

_____ type heavily dictates the replication cycle of the virus

-DNA or RNA, rarely both -single or double stranded

a viruses genome can either be _____ or _____. then the can either be _____ or _____

negative

all _____ RNA viruses are enveloped

helical

all _____ viruses have are enveloped

envelope

all human helical viruses have an _____

nucleocapsid

all proteins have a _____ composed of protein and nucleic acid

virus

an infective agent that typically consists of a nucleic acid molecule in a protein coat that replicates in a host cell -broad term. any point during life cycle (inside or out. packaged or unpackaged)

host transcriptional machinery in the nucleus

because viral DNA resembles host DNA, a viruses can use _____

no, a virus is specifically targeting a specific host cell. it has certain proteins to attach to certain host cell receptors

can a virus infect any cell?

- +RNA: acts like mRNA in human cells and can be translated by the host cell - -RNA: cannot be translated by human cell, so virus must contain RNA polymerase to copy the RNA strand into a +RNA strand.

compare + and - sense RNA

-DNA: double stranded -RNA: mostly single stranded, but can be double

compare DNA and RNA in number of strands

-DNA viruses are transcribed in the nucleus and use host cell DNA polymerases -RNA viruses are translated in the cytoplasm and bring their own RNA polymerase

compare location of transcription and translation of DNA and RNA viruses

-glycoprotein on virus binds to host receptor -the viral glycoproteins promote membrane fusion so both cells become one giant cell -nucleocapsid expelled into cytoplasm -host cell is marked with residual viral glycoproteins now (how immune system can recognize viral infected cells)

explain the process of endocytosis for enveloped viruses in the viral replication cycle

-virus binds to surface protein -stimulates receptor mediated endocytosis -virus is internalized in a vesicle -virus is released into the cytoplasm to unpack

explain the process of endocytosis for naked and enveloped viruses in the viral replication cycle

intrinsic capsid antigenic and cytotoxic

fiber proteins on adenoviruses are _____ structures for human immune cells to recognize the virus. they are _____ and _____ are are grooves in the capsid durface

disassembled self-assemble

for viruses replication, the initial virus is _____ during the infection process and viral components must _____

nucleic acid

helical capsids are coiled springs shaped by _____

rod

helical viruses are _____ shaped.

they can be released by budding through the membrane or cell lysis (like naked)

how are enveloped viruses released

-size: nm to micrometers -morphology: nucleocapsid shape and envelope characteristics -nucleic acid type and structure of nucleic acid

how can a virus be classified based on structure

antibodies bind to the host cell receptors, blocking viruses from binding to the receptor, the virus can then be internalized into the cell to be neutralized -used in vaccinations

how can antibodies block the adoption process of viral replication cycle

they have a groove in outer protein layer to interact

how do naked capsid viruses interact with human cells

viruses steal the functionality of already existing receptors on host cells and make them receptors for the virus.

how do viruses obtain host viral receptors

they have early and late genes that are transcribed. early genes include encoding for DNA polymerases and DNA binding proteins (replication and regulatory transcription proteins). late genes encode for structural and other proteins (capsid proteins for packaging)

how is DNA viruses gene transcription temporally regulated

they must be copied to the positive strands before they can be translated, so they must pack their own active RNE dependent RNA polymerase enzymes because human host cells will not have it.

how is negative sense RNA viruses translated

naked or enveloped

icosahedrals may be _____ or _____

triangular capsid subunit assembly

icosahedron capsids have _____ shaped capsomeres like a multi-sided dice. it is shaped by _____

naked capsid virus enveloped virus

if a virus only has a nucleocapsid, then it is considered _____. if it has a nucleocapsid and glycoproteins and membrane (stolen membrane from human cells), it is _____

nucleic acids

in a helical virus, the _____ are in a spiral inside the hollow chamber of the protomers

nucleic acids enzymes nucleic acid binding proteins -everything needed for replication

in a naked virus, the outer layer of capsid protein encases _____, _____, and _____

replication

in enveloped viruses, they modify and use the cell membrane for the envelope during _____

naked

in general, are naked or enveloped viruses more stable

glycolipids co-opted

in the adsorption process of viral replication cycle. the initial attachment of the virus uses surface proteins, or _____, and the host cell receptors (inter grins and other surface proteins) are _____

virion viral genome

in the viral replication cycle, the uncaring process is the disassembly of the _____, separating the _____ from the envelope and capsid

virion

the complete, infectious form of a virus outside a host cell -seen in a microscope -packaged

persistent (latent) nucleus cytoplasm virion

many DNA viruses establish _____ infections. viral DNA genomes must enter and reside in the _____. the mRNA is exported to the _____, and then the proteins are transported into the nucleus for _____ assembly

ssRNA dsDNA

most common virus types are _____ and _____

more

naked capsids are _____ resistant than envelope

cell lysis -do not have a membrane to go through, so just burst out

naked capsids are released by _____

temperature pH proteases detergents drying

naked capsids are resistant to _____ (5)

recognition host entry

naked viruses have virion surface structures (spikes or binding grooves) for receptor _____ and _____

spike hemaglutinins (HA)

on an envelope virus, the host cell recognizes the glycoproteins _____ proteins embedded in the membrane. another example of oral attachment proteins (VAP) are one that bind to erythrocytes causing them to clump, they are called _____

small

picornavirus is a very _____ RNA virus

mRNA translated

positive sense RNA viruses are functionally the same as _____ and can be immediately _____

binding

spike proteins function for _____

protein membrane lipids glycoproteins

structural components of enveloped viruses

protein only

structural components of naked capsid

capsid

the _____ of a nucleocapsid is a structural protein coat

glycoproteins

the _____ of enveloped viruses help bind the nucleocapsid to the stolen membrane

capsid (assembly with nucleic acid and lips envelope)

virion shapes are determined by inherent _____ structure

nucleic acid protein

viruses exclusively us ghost cell machinery and resources for _____ and _____ production

make new copies spread

viruses only role is to _____ and _____

assembly

viruses reproduce by new _____ of component parts

living cell -obligate intracellular parasite requiring eukaryotic cell

viruses require _____ to replicate

arbovirus

viruses spread by biting arthropods (insects, ticks) -means of transmission

adenovirus

viruses that target lymphatic tissues

enterovirus

viruses that target the GI system

viral attachment proteins (VAP) or structures

what does the human immune system recognize on viruses

stolen membrane from host cells and glycoproteins

what is an virus envelope composed of

copy its genome and makes RNA

what is the first thing a virus does once it unpacks itself inside a host cell

from budding though the ER of the host cell, or directly from the host cells membrane

where does a virus get its envelope

they are tethered to the membrane of the virus as it passes through the ER in a host cell

where does the influenza virus obtain the hemaglutinin spike

they are mostly single stranded, so they do not have another strand to compare and ensure no errors were made during replication

why are RNA viruses more prone to mutations?

-in their simplest form, they are a nucleic acid and proteins (and maybe a capsule) -they have no metabolic function, so do not create now energy or utilization ATP

why are viruses not quite considered living