BIO 246 Exam 2

What are the molecules from smallest to largest?

Acellular viruses, prokaryotes, and eukaryotes

What are viruses?

Acellular infectious particles

What does obligate intracellular parasite mean?

Requires a living host cell for reproduction

How many generations would it take one bacterial cell to produce a million cells by binary fission?

20

If 10 new viruses are produced from one host cell, how many generations does it take to produce a million viruses?

6

How do viruses reproduce?

One virus enters the host cell, the virus then uses the host cell “machinery” to make multiple copies of the virus, and dozens of viruses are released to infect dozens of other host cells

What structures do all viruses have?

Nucleic acid genome (genes for viral reproduction), protein capsid (to protect genes during transport), and spike proteins (for attachment to host cells)

What structures do some viruses have?

Lipid envelope (phospholipids surrounding the capsid)

What are the two types of viruses?

Naked and enveloped

What are viral genomes composed of?

DNA or RNA (both are genes)

What are capsids composed of?

Protein subunits called capsomers

What do capsids have for attachment to host cells?

Spike proteins

What are the two types of capsid shapes?

Helical (long tube) or polyhedral (many sides)

What is “stolen” from host cell membrane by viral budding?

Envelope

What is an envelope?

A phospholipid bilayer with viral “spike” glycoproteins

What is an example of an enveloped, polyhedral, RNA virus?

Human immunodeficiency virus (HIV)

What does a naked helical virus look like?

What is an example of a naked helical virus?

Tobacco mosaic virus (TEM)

What does a filamentous enveloped helical virus look like?

What does a spherical enveloped helical virus look like?

What is an example of an filamentous enveloped helical virus?

Ebola

What is an example of a spherical enveloped helical virus?

Influenza

What does a naked icosahedral virus look like?

What is an example of a naked icosahedral virus?

Adenovirus

What does an enveloped icosahedral virus look like?

What is an example of an enveloped icosahedral virus?

Hepatitis B virus

What is a bacteriophage?

A virus that infects bacterial cells and has a complex capsid

What does the polyhedral capsid of a bacteriophage contain?

The DNA genome

What does the helical sheath of a bacteriophage do?

Delivers DNA during infection

What do the tail fibers of a bacteriophage do?

Attachment

What is something scientists are looking into as antibiotic replacement?

Phage therapy

What are cytopathic effects?

Additional problems to cells viruses can cause outside of killing them

What are examples of cytopathic effects?

Latent viruses and oncoviruses

What is a chronic latent state?

A dormant state

What is an example of a chronic latent state virus?

Herpes (chickenpox —> shingles)

What are oncoviruses?

Cancer-causing viruses

What are two examples of oncoviruses?

1. HPV —> genital warts —> cervical cancer

2. Hepatitis virus —> hepatitis —> liver cancer

Who discovered the prion?

Stanley Prusiner

What is a prion?

Infectious protein particles that are acellular

What is a degenerative and deadly brain disorder?

Creutzfeldt-Jakob Disease (CJD)

What is Creutzfeldt-Jakob Disease (CJD) related to?

“Mad cow” disease in cattle, aka bovine spongiform encephalopathy (BSE)

What happened in Creutzfeldt-Jakob Disease to humans?

Accumulation of proteins that “clogged up” neurons and killed them causing holes in the brain

How does reproduction in prions occur?

In the absence of genes by a process called conversion

How do prions interact with their normal neural counterparts to create new prions?

Misfolding

What are BSE & CJD known as?

Transmissible spongiform encephalopathies (turn brain tissue spongey)

What are the steps of virus reproduction?

Adsorption, entry & uncoating, synthesis, assembly, and release

What is adsorption?

Adhering/attaching to

What is tropism?

the host-cell specificity of a virus

What is an example of tropism?

HIV has an envelope spike protein that binds to a receptor on human T cells

What is entry & uncoating?

Freeing the nucleic acid through endocytosis or fusion

What is endocytosis?

A naked or enveloped virus is brought into the cell by folding the outer membrane inward and uncoating the endosome to free the nucleic acid

What is fusion?

When an enveloped virus binds to the cell membrane and the envelope melts to enter into the cell to uncoat and free the nucleic acid

Who performs entry with no uncoating?

Bacteriophages (they introduce DNA directly into the host cell by injection)

What is synthesis?

Making copies of the virus by using materials from the host cell

What does nucleic acid synthesis do?

• Makes copies of viral genome

What does protein synthesis do?

• Makes viral enzymes

• Makes viral capsomers

• Makes viral envelope spikes and inserts in the host membrane

How can host cells help with viral synthesis?

Living cells gather and utilize energy and building blocks to maintain the flow of genetic information

What enzyme does DNA use to replicate and produce DNA 2x?

DNA polymerase

What enzyme does DNA use to transcribe and create mRNA?

DNA-dependent RNA polymerase

What does mRNA use to translate to proteins?

Ribosomes

What process turns v-DNA or v-proteins into new DNA viruses?

Assembly

How is the synthesis of an RNA virus different from a DNA virus?

RNA viruses require a viral enzyme because host cells cannot make copies of RNA from an RNA template (no host enzyme)

How does v-RNA synthesize to more v-RNA?

RNA-dependent RNA polymerase

How does v-RNA translate to v-proteins?

Ribosomes

How do v-proteins and v-RNA create new RNA viruses?

Assembly

How is the synthesis of an RNA retrovirus different?

RNA retroviruses also require a viral enzyme but the enzyme does not directly synthesize RNA: it makes DNA instead

How does v-DNA transcribe to create v-mRNA?

DNA-dependent RNA polymerase

How does v-RNA reverse transcribe to v-DNA?

Reverse transcriptase

“Copying” enzymes of RNA viruses have ____

Low fidelity

Why are enzymes error prone?

They have a high mutation rate

What is an example of RNA-dependent RNA polymerase?

SARS-CoV-2 replicase

What is an example of reverse transcriptase?

HIV RT

What is integration?

Some viruses incorporate their genomes into the host chromosome

When HIV uses integrase to recombine the copy of the viral DNA into a host chromosome, it results in what?

Latency

What is latency?

When a virus is dormant and the host is unaware of infection

What is lysogeny?

When bacteriophage inserts their DNA into the bacterial chromosome which results in dormant prophage

What is assembly in virus reproduction?

When newly synthesized viral genomes and structural proteins come together to form new, individual virus particles

What occurs during assembly of virus reproduction?

Capsomers bind to viral DNA or RNA to form the “naked” nucleocapsid; envelope spike proteins are then inserted into the host membrane and recruit nucleocapsids from the cytosol to form viral buds

How are enveloped viruses released from the cell and where does it get its envelope from?

Budding; part of the cell membrane

How are naked viruses released from the host cell?

Lysis (the cell breaks and releases all of the virus particles)

What does lysis produce?

Plaques (areas of cell death/empty space in the cell layers) in cell culture

How do bacteriophages kill bacterial cells?

By lysis

What is lysis by bacteriophages useful for?

phage therapy

List microbes from least resistant to most resistant.

enveloped viruses, most gram-positive bacteria, fungi and fungal spores, most gram-negative bacteria, protozoan trophozoites, protozoan cysts, staphylococcus and psuedomonas, mycobacterium, bacterial endospores, and prions

Why are myobacterium resistant to elimination?

Waxy cell wall

Why are bacterial endospores resistant to elimination?

They have an extremely tough spore coat

Why are prions resistant to elimination?

They are simple; no genes; protein is already misfolded

What are the levels of decontamination?

Sterilization, disinfection, antisepsis, sanitization, and degermation

What is sterilization?

The destruction or removal of ALL viable microbes including endospores and viruses from inanimate objects

What is an example of sterilization?

Surgical/dental instruments are sterilized in an autoclave before use

What is disinfection?

The destruction or removal of vegetative pathogens but not endospores (can also remove toxins) from inanimate objects/surfaces

What is an example of disinfection?

You disinfect a countertop with bleach after handling raw meats

What is antisepsis?

The destruction of inhibition of vegetative pathogens but not endospores from living tissues (skin & mucous membranes)

What is an example of antisepsis?

An alcohol wipe is used on skin before a needle injection

What is sanitization?

Reduction in the number of microorganisms to acceptable levels on inanimate objects/surfaces

What is an example of sanitization?

Dishes are washed with soap/detergent and warm/hot water in a restaurant

What is degermation?

Reduction in the number of microorganisms on living tissues (human skin)

What is an example of degermation?

Washing hands after you have been in contact with fomites in public places and before you touch your eyes, nose, or mouth

What are physical methods for decontamination?

• High temperature

• Low temperature

• Dehydration/osmotic pressure

• Radiation

• Filtration

What is moist heat used for?

To denature and/or coagulate microbial proteins (inactivates enzymes; disrupts structure)