Chapter Six: A Cellular Pathogens (Video)

40-question Q&A flashcards covering acellular pathogens, viral structures, replication cycles, and gene transfer.

What is an acellular pathogen as described in Chapter Six?

An entity lacking a cell, plasma membrane, and ribosomes that infects a cell to hijack its machinery; includes viruses, viroids, virusoids, and prions.

Which four categories are included under acellular pathogens?

Viruses, viroids, virusoids, and prions.

What is a viroid and which organisms do they typically infect?

A very small circular RNA that infects plants.

What is a virusoid and what does it require to replicate?

A single circular strand of RNA that requires a helper virus to replicate.

What are prions?

Infectious proteins that lack nucleic acids and can cause neurodegenerative diseases.

Is the hepatitis D virus an example of a virusoid, and why?

Yes; it is a virusoid that causes pathology only when hepatitis B is present.

Are viruses considered living organisms? Why or why not?

No; they are acellular and cannot reproduce or metabolize without a host cell.

What is a virion?

A fully assembled infectious viral particle.

What are the possible nucleic acid types found in viruses?

DNA or RNA; can be single- or double-stranded.

What protects a viral genome inside a virion?

A capsid built from capsomers; some viruses also have an envelope.

What is a viral envelope and its role?

A lipid membrane surrounding some virions with spikes that mediate host interactions.

What are capsomers?

Subunits that assemble to form the viral capsid.

What does the term host range describe in viruses?

The species and/or cell types a virus can infect.

What is a bacteriophage?

A virus that specifically infects bacteria.

Describe a helical virus and name examples.

Rod-shaped viruses with a cylindrical capsid; Ebola and rabies are examples.

Describe a polyhedral virus and give examples.

A virus with a 20-faced icosahedral structure; examples include adenovirus and poliovirus.

What characterizes an enveloped virus?

A virus enclosed in a lipid envelope around the capsid; includes influenza and herpesviruses.

What are key structural components of bacteriophages involved in infection?

Tail fibers (landing), base plate, pins, and the sheath that injects DNA.

What type of genome do most bacteriophages have?

Double-stranded DNA.

What are the two main replication cycles for bacteriophages?

The lytic cycle and the lysogenic cycle.

What happens during the lytic cycle of a bacteriophage?

Attachment and penetration, biosynthesis, maturation, and release leading to lysis of the host.

What is a prophage?

The viral genome integrated into the host chromosome during lysogeny.

What triggers the induction of a prophage into the lytic cycle?

Environmental cues (e.g., UV light or chemicals) that cause induction.

What is phage conversion?

A lysogenic phage introduces new genes into the host genome, potentially altering traits.

What is specialized transduction?

A lysogenic phage sometimes carries bacterial genes with its genome and transfers them to a new host.

How are mitochondria evolutionarily related to bacteria?

Mitochondria are descendants of bacteria via endosymbiosis.

What are retroviruses?

RNA viruses that use reverse transcriptase to copy RNA into DNA and integrate into the host genome as proviruses.

What roles do integrase and protease play in retroviral life cycles?

Integrase inserts viral DNA into the host genome; protease processes viral proteins during maturation.

What is budding in viral release?

Enveloped viruses acquire an envelope from the host membrane during release via budding.

What do H spikes and N spikes stand for in influenza viruses?

H stands for hemagglutinin; N stands for neuraminidase, spikes that determine host range and virion release.

Why are flu vaccines updated every year?

Because influenza undergoes rapid mutations in surface proteins, requiring new vaccines.

What alternative cell culture method is increasingly used to grow influenza viruses?

Canine kidney cells, used to reduce mutation rates compared to chick embryos.

What does Tamiflu target?

Neuraminidase to inhibit virion release.

What is zidovudine (AZT) and its antiviral target?

A nucleoside analog that inhibits reverse transcriptase in HIV.

What is Remdesivir and how does it work?

A ribonucleotide analog that inhibits viral RNA polymerase.

How do viroids differ from viruses?

Viroids are tiny circular RNAs without capsids; viruses have nucleic acids enclosed in a capsid and sometimes an envelope.

What is a virusoid's requirement for replication?

It lacks a capsid and requires a helper virus to replicate.

What is prion disease and its stability?

Infectious misfolded proteins causing neurodegenerative diseases; highly heat resistant.

What are the three modes of horizontal gene transfer?

Conjugation, transformation, and transduction.

What is conjugation and what plasmid enables it in Gram-negative bacteria?

Direct transfer of plasmids via a sex pilus; requires the F (fertility) plasmid in the donor.