Chapter 13 MICRO – Flashcards

Cause many infections of humans, animals, plants, and bacteria. Consists of nucleic acid molecule in a protein coat and is able to multiply only with in the living cells of a host.

Viruses lack a cell structure, they cannot exist independently from a host cell, and they can infect both prokaryote and eukaryote organisms. Eukaryotic cells have a nucleus and organelle.

Complete, infective form of a virus outside a host cell

A core of RNA or DNA and a capsid (protein coat)

A virus with a membrane

Phospholipid bilayer and proteins

The capsid is removed, a virus without its capsid exists solely as nucleic acid but is still referred to as a virus

DNA or RNA

Double-stranded DNA, single-stranded DNA, single-standed RNA, and double-stranded RNA

3 genes to 4000 genes

The precise affinity of viral surface proteins or glycoproteins for complementary proteins or glycoproteins on the surface of host cell

Archaea, bacterial, plant, protozoan, fungal, and animal cells

A virus that infects bacteria

No, they are too small

Proteinaceous subunits called capsomeres

Protection for viral nucleic acid and means of attachment to hosts cells

Helical - capsomeres that bond together in a serial fashion to form a tube round the nucleic acid Polyhedral - roughly spherical, with a shape similar to a geodesic dome Complex - have capsids of many different shaped that do not readily fit into either of the other two categories

Icosahedral heads, which contain the genome, attached to helical tails with tail fibers

A naked virion lacks cell membranes, but an enveloped virion has a cell membrane surrounding their capsids.

Phospholipid bilayer and proteins; some proteins are virally-coded glycoproteins (spikes)

Family than genus

Viruses - inert macromolecules outside of a cell but become active inside a cell, do not divide or grow, acellular, obligate intracellular parasites, contain either DNA or RNA, with few exceptions, genome can be dsDNA, ssDNA, dsRNA, ssRNA, usually ultramicroscopic in size, have a proteinaceous capsid around genome; some have an envelope around capsid, and replicate in an assembly-line manner using the enzymes and organelles of a host Cells - metabolize on their own, divide and grow, cellular, most are free living, contain both DNA and RNA, genome is dsDNA, surrounded by a phospholipid membrane and often a cell wall, and self replicating by asexual and or sexual means

They lack genes for all the enzymes necessary for replication, nor do they possess functional ribosomes for protein synthesis

Their hosts enzymes and organelles to produce new visions

Virus that infects bacteria

Composed of a protein coat surrounding DNA or RNA

1. Attachment - proteins on tail fibers attach to host cell 2. Entry - nucleic acid is "injected" into the host cell 3. Synthesis - all different parts of the bacteriophage are made proteins and tail fibers 4. Assembly - all parts are put together 5. Release - new phages burst out of cell, which destroys the cell

Dormant stage, not actively making new viruses, modified replication cycle in which infected host cells grow and reproduce normally for many generation before they lyse.

Bacteriophage that does not immediately kill its host

An inactive bacteriophage, which is inserted into a hosts chromosome.

In virology, excision of a prophage from the host chromosome, at which point the prophage reenters the lytic phase

1. Attachment - proteins on tail fibers attach to host cells 2. Entry - Nucleic acid in "injected" into host cell 3. Prophage - viral DNA incorporated into host DNA in chromosome 4. Replication - of chromosome and cell division 5. Induction - a stress or trigger that will begin lytic cycle

The lytic steps of synthesis, assembly, and release resume from the point at which they stopped.

Ultraviolet light, X rays, and carcinogenic chemicals

1. Attachment - dependent on the chemical attraction and exact fit between proteins or glycoproteins on the virion and complementary protein or glycoprotein receptors 2. Entry - three different mechanisms: direct penetration, membrane fusion, and endocytosis 3. Synthesis - different strategy for DNA or RNA and whether single-stranded, double-stranded 4. Assembly 5. Release

Naked viruses - released one of two way either they may be extruded from the cell by exocytosis or they may cause lysis and death of the cell Enveloped viruses - released via budding

Enveloped viruses because the host cell shed viruses slowly and relatively steadily

An animal virus that remains inactive for a long period of time before becoming active

HIV, chicken pox, and herpes virus

Prolonged for years with no viral activity (signs or symptoms)

Bacteriophage - proteins on tails attach to proteins on cell wall, genome is injected into cell or diffuses into cell, site of synthesis and assembly is in cytoplasm, mechanism of release is lysis, and nature of chronic infection is lysogen always incorporated into host chromosome, may leave host chromosome Animal virus - attachment spikes, capsids, or envelope proteins attach to proteins or glycoproteins on cell membrane, capsid enters cell by direct penetration, fusion, or endocytosis, removal of capsid by cell enzymes, site of synthesis and assembly is RNA viruses in cytoplasm and DNA viruses in nucleus, mechanism of release is naked visions; exocytosis or lysis, enveloped visions; budding, latency with or without incorporation into host DNA; incorporation is permanent.

As long as protooncogenes (genes that play a role in cell division) are repressed, no cancer results. but when active cancer can develop, several genetic changes muct occur before cancer develops

Proteinaceous infective particles

Bovine spongiform encephalitis (mad cow disease), spare in sheep, kuru (human disease that has been eliminated), chronic wasting disease in deer and elk and variant creutzfeldt-jakob disease in humans

By incineration or by autoclaving in concentrated sodium hydroxide

Viruses use sophisticated methods to invade cells, have the means of taking control of their host cells, and posses genomes containing instructions for replicating themselves