Microbiology Exam #3

Define host

An organism that a virus infects and replicates inside.

Define virus

A non-living infectious agent made of nucleic acid (DNA or RNA) enclosed in a protein coat.

Define phage

A virus that specifically infects bacteria (bacteriophage).

Define prion

A misfolded protein that causes infectious diseases in animals by inducing normal proteins to misfold.

Define antigenic drift

Small mutations in viral genes over time that lead to changes in surface proteins, reducing immune recognition.

Define antigenic shift

A major change in a virus's genome due to genetic reassortment, creating a new subtype that can lead to pandemics.

What is the function of the viral genome?

Contains the genetic information required for viral replication and infection. It can be DNA or RNA, single- or double-stranded.

What is the function of the capsid?

Protects the viral genome and helps in attachment to host cells. Made of protein subunits called capsomeres.

What is the nucleocapsid?

The combination of the viral genome and capsid.

What are virus attachment proteins?

Proteins (e.g., spike proteins) that help viruses attach to and enter host cells.

What is the function of the matrix protein?

Links the viral envelope to the capsid, providing structural support.

What is the viral envelope?

A lipid bilayer derived from the host membrane that surrounds some viruses, aiding in entry and exit.

What do viral genes encode for?

Structural proteins (capsid, attachment proteins), enzymes for replication, and regulatory proteins.

Why do viruses infect specific hosts or tissues?

Due to specific interactions between viral attachment proteins and host cell receptors.

What are the shapes of viruses?

Icosahedral, helical, and complex.

What is antigenic drift?

Gradual mutations in viral genes leading to changes in surface proteins.

What is antigenic shift?

A major genetic change, often due to reassortment between two viruses.

Name one antiviral and its target.

Oseltamivir (Tamiflu) targets viral release by inhibiting neuraminidase.

Why are viruses not considered living organisms?

They cannot reproduce or carry out metabolism without a host.

Example of a DNA virus.

Herpesviridae; double-stranded DNA; icosahedral capsid; enveloped.

Example of an RNA virus.

Retroviridae (HIV); single-stranded RNA; reverse transcriptase; enveloped.

What are protozoa?

Single-celled eukaryotic microbes that live in moist environments and reproduce asexually or sexually.

What are fungi?

Eukaryotic microbes that can be unicellular (yeasts) or multicellular (molds). They reproduce via spores and decompose organic matter.

What are helminths?

Multicellular parasitic worms (e.g., roundworms, tapeworms) that live in hosts during part of their lifecycle.

Define definitive host.

The host where a parasite reaches maturity and reproduces sexually.

Define intermediate host.

The host where a parasite undergoes larval development or asexual reproduction.

Define trophozoite.

The active, feeding stage of a protozoan.

Define cyst.

The dormant, protective stage of a protozoan.

Define yeast.

Unicellular fungi that reproduce by budding.

Define hyphae.

Long, thread-like structures that make up the body of multicellular fungi.

Define mycelium.

A network of hyphae that forms the body of a fungus.

Define mushroom.

The reproductive structure of some fungi, producing spores.

What are the three lines of defense?

1. Physical barriers (skin, mucous). 2. Innate immunity (phagocytes, inflammation). 3. Adaptive immunity (B/T cells).

What is the difference between innate and adaptive immunity?

Innate: Non-specific, fast. Adaptive: Specific, slower, has memory.

Define macrophages.

Phagocytes that engulf and digest pathogens and present antigens to T cells.

Define neutrophils.

Short-lived phagocytes that are the first responders to infection.

What is antigen presentation?

The process by which macrophages or dendritic cells present antigens to T cells to activate them.

What is the structure of an antibody?

Y-shaped protein with variable regions for antigen binding and constant regions for immune signaling.

What are the functions of antibodies?

Opsonization, neutralization, immobilization, and antibody-dependent cytotoxicity.

How do vaccines work?

They stimulate the immune system to produce memory cells without causing disease.

What are the types of vaccines?

Live attenuated, inactivated, subunit, and nucleic-acid based.