Microbiology: Module 7

Capsid

the protein coat that protects the nucleic acid of the virus is called the

Bacteriophages

Viruses that infect bacteria are called

Lytic

In the ____ cycle, all infected cells are eventually killed by breaking open to release virus particles

sometimes convert their genome to DNA for replication

RNA Viruses

Nucleus

The genome of influenza virus is replicated in the host cell’s ____

Plaque

A zone of clearing on a lawn of bacteria due to viral infection is called

Virion

is a complete, fully developed infectious viral particle

Prion

An infectious protein is called a

No. They are not considered alive because they are acellular and cannot reproduce on their own.

Are viruses considered living organisms?

Acellular (they are not made of cells)

Are viruses cellular or acellular?

No. They require a host cell to propagate (replicate)

Can viruses reproduce independently?

Genome and capsid

What are the two essential components found in all viruses?

DNA or RNA

What can a viral genome consist of?

No. Some viruses are enveloped, while others are naked (non-enveloped)

Do all viruses have an envelope?

enveloped virus

A virus surrounded by a lipid envelope outside the capsid.

naked virus

A virus that lacks a lipid envelope and consists only of a genome and capsid

No. Some viruses have complex structures

Are all viruses the same shape?

Complex (ex: bacteriophage)

What capsid shape is this?

Icosahedral (ex: Rhinovirus)

What capsid shape is this?

Helical (Tobacco mosaic virus)

What capsid shape is this?

• Genome

• Capsid

• No lipid envelope

Naked virus

• Genome

• Capsid

• Lipid envelope

• Glycoprotein spikes

Enveloped virus

Enveloped viruses

Which viruses have a lipid membrane?

Help the virus attach to host cells.

What is the function of glycoprotein spikes?

Capsid

Which part contains the viral genome?

Tail fibers

Which structure attaches to the bacterial cell?

Injects viral DNA into the bacterium

What is the function of the sheath?

Lytic cycle and lysogenic cycle

What are the two main viral life cycles?

Lytic cycle.

Which viral cycle immediately kills the host cell?

Attachment → Penetration → Biosynthesis → Assembly → Release (lysis)

What are the five steps of the lytic cycle?

The virus binds to specific receptors on the host cell.

What happens during attachment? (lytic)

They can only bind to cells with the correct receptors

Why can't viruses infect every cell? (lytic)

Viral nucleic acid enters the host cell.

What happens during penetration? (lytic)

Only the viral DNA (or RNA); the capsid remains outside

In bacteriophages, what enters the host cell? (lytic)

The virus takes over the host's machinery to make viral DNA and viral proteins

What happens during biosynthesis? (lytic)

Viral genomes and capsid proteins assemble into complete viruses

What happens during assembly? (lytic)

The host cell lyses (bursts open).

How are viruses released? (lytic)

It dies.

What happens to the host cell during the lytic cycle?

Viral DNA integrates into the host chromosome

What happens after penetration? (lysogenic)

A prophage

What is viral DNA called after integrating into bacterial DNA? (lysogenic)

It is copied every time the bacterial chromosome replicates.

What happens while the prophage is integrated? (lysogenic)

No

Are new viruses produced immediately during the lysogenic cycle?

induction

The prophage leaves the bacterial chromosome and enters the lytic cycle. (lysogenic)

Stress such as UV light, radiation, or chemicals

What can trigger induction? (lysogenic)

prophage

Viral DNA integrated into a bacterial chromosome. (lysogenic)

The prophage is copied along with the bacterial DNA

During lysogeny, what happens when the bacterium divides?

Lytic

Which cycle immediately produces new viruses?

Lysogenic

Which cycle allows the virus to remain dormant?

Lysogenic

Which cycle contains a prophage?

Lysogenic

Which cycle can switch into the lytic cycle?

Double-stranded DNA

Can generally use host proteins for replication

Single-stranded DNA

• Needs some host proteins for replication

• Uses virus-specific DNA-dependent DNA polymerase

Double-stranded RNA

• Uses virus-specific RNA-dependent RNA polymerase

• Brings replication proteins into the cell with the genome

Single-stranded (+) RNA

• Can act as mRNA immediately upon entering the cell

• Uses virus-specific RNA-dependent RNA polymerase for replication

• Brings replication proteins into the cell with the genome

Single-stranded (-) RNA

• Uses virus-specific RNA-dependent RNA polymerase for replication

• Brings replication proteins into the cell with the genome

Retroviruses

• Enters cell as RNA, converted to DNA

• Uses Reverse transcriptase

• Brings replication proteins into the cell with the genome

prion

An acellular, infectious, misfolded protein.

no

Do prions contain DNA or RNA?

It causes normal proteins of the same type to misfold

What makes a prion infectious?

The normal protein misfolds and becomes another prion.

What happens when a normal protein contacts a prion?

By converting normal proteins into misfolded prion proteins

How do prions spread within the body?

They damage or kill affected cells.

What do prions do to cells?

Through genetic mutations passed down in families

How can prion diseases be inherited?

Misfolded proteins accumulate, disrupting normal cell function and causing cell death

Why are prions harmful?

By consuming contaminated food or exposure to infectious prions

How can prion diseases be acquired?

yes

Can prions be both inherited and infectious?

They are extremely resistant to destruction.

Why are prions difficult to eliminate?

No

Is normal cooking enough to destroy prions?

Prions are highly resistant to heat and standard cooking methods

Why doesn't cooking make prion-contaminated food safe?