BIOG251 Chapter 5: Viruses

Covers bacterial and animal viruses, and important terms surrounding viruses.

Virus

Obligate intracellular parasites, are not made of cells, antibiotics are not able to treat them

Viruses need what to be able to reproduce?

Be inside of a host cell

Virion

Viruses that are able to establish infections

Virome

The viruses associated with the human body

How can viruses vary?

Whether the genetic material is DNA or RNA, the shape, the host(s) it can infect

Capsid

The protective protein shell surrounding a virus

Capsomere

The protein subunit that creates the capsid

Nucleocapsid

When the capsid is combined with the viral genetic material

Naked viruses

Lack an envelope, only require a capsid

Enveloped viruses

Have an extra external covering that comes from the host cell’s membrane when the virus is released

Spikes

Allow a virus to physically connect to the host cell

Susceptible cell

Has a receptor for a given virus

Resistant cell

Does not have a receptor for a given virus

Permissive cell

Supports viral replication

A virus can only replicate in cells that are…

Permissive and susceptible

Host range

The hosts that a virus can infect

Viral replication process

Attachment → entry → uncoating → synthesis → release

Adsorption/attachment

Spike and host receptor interaction

Entry

The virus enters the cell

Types of viral entry

Endocytosis, fusion, nucleic acid only

Endocytosis

The entire virus is engulfed

Fusion

The virus fuses with the host’s cell membrane

Nucleic acid only entry

The viral genetic material is inserted into the host cell

Uncoating

The viral genome exits the capsid

Synthesis

The virus replicates its genome and makes proteins

DNA viruses enter…

The nucleus

RNA viruses enter…

The cytoplasm

Release

Newly made visions leave the cell

Viral methods of release

Lysis, exocytosis, budding

Lysis

The host cell ruptures and bursts, leading to cell death

Exocytosis

Active transport out of the host cell

Budding

Reverse endocytosis

Oncovirus

Mammal viruses that can initiate tumor growth

Transformed cells

Cells that lack checkpoints and divide indefinitely

Retroviruses

Viruses that encode their genome as RNA

Most viruses that cause cancer are…

Retroviruses

Oncogene

Gene that can initiate tumor growth

Bacteriophage

A virus that only infects bacteria

Temperate phage

A virus that enters the host and does not immediately begin replication

Prophage

A virus put into the bacterial genome that is inactive and copied during cell division

Induction

Activates replication of a prophage

Lysogeny

Host carriers viral DNA as part of its chromosome

Lysogenic conversion

A bacterium gains a trait from a virus

Prion

Misfolded infectious proteins

PrPc

Stabilizing protein for brain cells

PrPsc

The infected protein for brain cells

Protease

Destroy misfolded proteins

Prions are resistant to the enzyme…

Protease