Viruses

virus

an infectious particle consisting of little more than genes packaged in a protein coat

5 differences between bacteria and viruses

living vs non living, live anywhere vs infect a host, larger vs submicroscopic, localized vs systemic

Examples of Bacteria

pneumonia, tetanus, food poisoning

Examples of Viruses

HIV, influenza, Covid, and Epstein Bar

capsid

Outer protein coat of a virus and houses the genetic material

capsomere

subunit of the capsid

Virus dna types

helical(helix), polyhedral, spherical, complex

capsid shapes

Rod-shaped, polyhedral, spherical

Steps of virus infection

attachment, entry, replication and assembly, egress (release)

attachment

when a virus attaches to a host cell, it binds to specific receptors for the capsomeres

entry

a host cell takes in the entire virus through endocytosis, or it attaches to the host cell and injects its genetic material into the host cell

replication and assembly: DNA

DNA serves as the genetic material for the virus, and is incorporated into the host cell, mRNA is then transcribed, and capsid proteins are made via translation, the DNA is then duplicated

replication and assembly: RNA

RNA is the genetic material for a virus, sometimes complementary RNA is made, capsid proteins are translated from mRNA, and RNA is copied for other viruses to have

replication and assembly: RNA retrovirus

Reverse transcriptase reverse transcribes RNA into DNA, and the new DNA is added to the host cell's DNA, where it goes through normal transcription and translation and produces viral DNA

Egress

the virus is detached from the host cell and causes its death via lysis or the virus detaches in a way that the host cell can be reused

reverse transcriptase

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

viral envelope

extra layer of protection around the capsid, but are only produced when a virus comes into contact with a host cell

host range

The limited range of host cells that each type of virus can infect, some viruses can infect almost all life, but others can only infect humans

Viral replicative cycle

virus taken into host cell via endocytosis and is then separated into two parts, capsid proteins and DNA, some viral DNA is replicated while others is transcribed and translated into capsid proteins, all of the viral DNA and capsid proteins are reassembled into viruses and leave the cell

the lytic cycle

a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses

virulent phages

reproduce strictly through the lytic cycle and always kill their host cells

the lysogenic cycle

a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA

temperate phage

A phage that is capable of reproducing by either the lytic or lysogenic cycle.

prophages

form when phage DNA integrates into the bacteria chromosome

phage lambda

temperate phage that injects its DNA into the host cell, and then can use either the lytic or lysogenic cycles

retrovirus

virus that contains RNA as its genetic information

HIV and its replication

retrovirus that causes AIDS, enters a host cell and its reverse transcriptase molecules are released, viral DNA then enters the nucleus and integrates into the DNA of a chromosome, the integrated provirus never leaves, remaining a permanent resident of the cell

Replicative cycle of enveloped RNA viruses

RNA virus binds to receptors on the host cell via glycoproteins, which causes the host cell to take in the virus via endocytosis, the host cell rapidly degrades the capsid, isolating the RNA, which serves as a template to make complementary RNA, some of that is used to make more, while the rest is used to translate more glycoproteins and capsid proteins, which are all reassembled to form a capsid and viral envelope around the viral RNA

Replicative cycle of HIV

Binds to receptor of WBC via glycoproteins, which takes in the virus via endocytosis, where the HIV disassembles exposing its RNA and reverse transcriptase, which catalyzes DNA forming a DNA RNA complex, a second DNA strand is then made, forming a double strand DNA which is inserted into the DNA of the WBC forming a provirus. This provirus then makes new RNA to act as the genome for future HIVs, mRNA is also translated to make new capsid proteins and glycoproteins and reverse transcriptase, everything is then assembled and exported

provirus

a virus that has become part of the DNA of a host cell

horizontal transmission

virus typically enters by way of damaged plant tissue, from pollen, another plant, or vectors such as insect bites

vertical transmission

virus is transmitted from the parent plant

hyperplasia

galls(tumors)

hypoplasia

thinned yellow splotches on leaves

cell necrosis

dead blackened stems, leaves, or fruit

viroids

small circles of RNA, mainly infect large amounts of crops, only seen in plants and can replicate within cells

components of a vaccine

live virus, killed virus, and molecular subunits, give a very small risk of infection

prions

proteinaceous infectious particles, very small with no nucleic acid, but cause fatal neurodegenerative diseases