Exam 3 Flashcards by Sonjia Wortham

Why do most scientists agree that viruses are nonliving entities?

they are not cells

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Isolated picornavirus virions would be expected to carry out which of the following types of metabolism?

not respiration or fermentation of glucose

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‘Capsid’ of a virus refers to which of the following:

protein shell of a virus

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T/F Helical and icosahedral are terms used to describe the shapes of a virus envelope.

false

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T/F ‘Nucleocapsid’ of a virus refers to a viral genome.

False

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What are bacteriophages?

viruses that kill bacteria

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T/F After the entry step bacteriophages leave their proteinaceous particles outside the bacterial cell.

True

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T/F The basic mechanism of viral multiplication is similar for all viruses.

True

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Bacteriophages undergo replication by:

Lytic cycle and/or lysogenic cycle

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Virulent phages are:

lytic

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The order of lytic cycle is:

adsorption-injection of genetic material- biosynthesis-maturation- lysis and release

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A clear area against a confluent “lawn” of bacteria is called a

plaque

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Bacteriophages mediate what kind of horizontal gene transfer between bacterial cells?

transduction

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The viral genome integrated into the bacterial genome is called:

prophage

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During which phase of their replication the bacteriophage release lysozyme

maturation

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Generalized transduction:

transfers a different portion of bacterial DNA each time

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Specialized transduction:

transfers a specific portion of bacterial DNA

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Acquisition of new traits (such as virulence factors) by bacterium because of viral infection is called:

lysogenic conversion

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A virus’s ability to infect an animal cell depends primarily upon the

presence of receptor sites on the cell membrane

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Which of the following statements about viruses is FALSE?

viruses use their own catabolic enzymes

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Nucleic acid from virions of which of the following could be directly translated by host cell ribosomes after the nucleic acid enters the cytoplasm?

a picornavirus

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A virus is said to have a minus sense RNA genome. This means that:

the viral genome is complementary to viral mRNA

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Virions of the -sense RNA viruses must include:

RNA dependent polymerase

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Genome of Herpes viruses is:

dsDNA

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An example of a latent viral infection is

cold sores

Which virus has its genome separated into 8 segments?

influenza virus

Influenza virus has what type of nucleic acid in its virions?

negative sense RNA

Which of the following are infected by the largest diversity of influenza viruses?

birds

What contributes to antigenic shift in influenza viruses?

a segmented genome

Genome of HIV virus is:

+ssRNA

T/F HIV is a retrovirus.

True

Reverse transcriptase catalyzes which of the following:

copies RNA to make DNA

HIV virus infects:

T cells (lymphocytes)

Viral envelope is acquired during which of the following steps?

release

Which of the following is a ‘naked” virus (the one that does not have an envelope)

rhinovirus

A persistent infection is one in which:

the disease process occurs gradually over a long period

T/F Viroid is a complete, infectious viral particle.

False

Which of the following is correct about viroids?

do not encode any proteins

T/F Prion is an infectious protein.

False

Mad-cow disease and Kuru are caused by:

prions

Which of the following protect the skin and mucous membranes from infection:

saliva, multiple layers of cells, tears, and the cillary escalator

A child falls and suffers a deep cut on her leg. The cut went through her skin, and she is bleeding. Which of the following defense mechanisms will participate in eliminating contaminating microbes?

phagocytosis and inflammatory response

Cells involved in innate immunity:

macrophages and neutrophils

Macrophages are

phagocytic

T/F Complement activation’ is a result of phosphorylation of complement proteins.

False

Complement-mediated lysis of infected cells is achieved by:

formation of the MAC, which is particularly effective against Gram-negative bacteria

Interferons are proteins (cytokines) released by some cells to fight:

viral infection

Clearing of virus infected cells is accomplished by which cells?

Natural Killer (NK) cells

B and T cells are involved in which immunity type?

adaptive immune response

Which of the following are NOT lymphocytes?

M cells

Which of the following is NOT a characteristic of B cells?

they recognize antigens associated with MHC

Which of the following is the best definition of epitope?

specific regions on antigens that interact with antibodies

The specificity of an antibody is due to:

the variable portions of the H and L chains

IgM antibodies

first produced during initial infection

IgA antibodies:

present in mother’s milk

Which of the following makes IgG (IgM, IgE, IgA etc.) antibodies?

plasma B cell

T/F Individual Plasma B cell produces many different antibody molecules.

False

T/F Different clones of Plasma B cell produce identical antibody molecules.

False

Which of the following bacterial components would most likely result in B cell stimulation by T-independent antigens?

bacterial capsule

Which of the following is a possible outcome of antigen-antibody reaction?

opsonization, activation of complement, agglutination, and antigen neutralization

When an antibody binds to a toxin, the resulting action is referred to as:

neutralization

Reverse transcriptase of HIV virus lacks ‘proofreading activity’ (in other words makes many mistakes during reverse transcription of viral RNA to dsDNA). This can explain why HIV virus:

rapidly mutates and escapes the neutralization by produced antibodies

In classical complement pathway, C1 protein binds to:

Fc (constant) region of antibodies bound to pathogen’s surface proteins

T/F Activation of complement results in an interference with viral replication in infected cell.

False

Which of the following is NOT a characteristic of cellular immunity?

naïve B cells make antibodies

The adaptive immune system can be divided into two groups: ‘Humoral’ and ‘Cell mediated’. Which of the following are part of the ‘Cell mediated Immune system’?

CD8+ T cells

These are secreted by T cells and function as a signaling molecules:

cytokines

Clonal selection of T cells (i.e. activation and proliferation) takes place in:

lymph node

T/F Antigen-binding receptors of T cells are identical to antigen-binding receptors of B cells.

False

Antigen-presenting molecules are:

MHC proteins

Which of the following cells are NOT an APC (antigen presenting) cells?

natural killer cells

Cytokines released by TH cells:

activate CD8+ T cells to CTLs

Which of the following destroys virus-infected cells?

CTLs

A Treg (regulatory T cells) cell deficiency could result in:

autoimmunity

What type of immunity results from vaccination?

artificially acquired active immunity

What type of immunity results from transfer of antibodies from one individual to another individual by means of injection?

artificially acquired passive immunity

What type of immunity results from recovery from mumps?

naturally acquired active immunity

Newborns' immunity due to the transfer of antibodies across the placenta is an example of:

naturally acquired passive immunity

A DNA plasmid encoding a protein antigen from West Nile virus is injected into muscle cells of a horse. This is an example of a(n):

nucleic acid vaccine

A patient shows the presence of antibodies against diphtheria toxin. Which of the following statements is FALSE?

The patient was near someone who had the disease

Purified protein from Bordetella pertussis is used in a(n)

subunit vaccine

Toxoid vaccines, such as the vaccines against Diphtheria and Tetanus, elicit a(n):

antibody response against these bacterial toxins

Capsule polysaccharide plus diphtheria toxin is a(n):

conjugated vaccine

Injection of purified antibodies is an example of what kind of vaccine?

toxoid vaccine

An inanimate object that may be contaminated with a pathogen is called a:

fomite

One example of infectious disease transmission by a fomite is:

a child developing a cold after playing with a toy that harbored rhinovirus

T/F LD50 is the number of bacterial cells that will cause an infection in 50 percent of the test population.

False

T/F ID50 is the number of bacterial cells that will result in death of 50 percent of the test population.

False

Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to:

super antigens

T/F Superantigens are the endotoxins that attach to MHC and T cell receptor.

False

Which of the following is TRUE?

endotoxins are part of the bacterial cell wall

The toxic component of lipopolysaccharide is called:

lipid A

T/F The “B” segment of the A-B toxin is responsible for its toxic enzymatic activity.

False

Endotoxin is released when:

Gram-negative pathogens lyse or divide

IgE antibodies

promote allergies

igG antibodies

most abundant in blood