MicroBio UNIT 3 (Review & Discussion) Ch 12 - 16

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Mrs. (Thomas) Wick's BIO 225 CCTC Spring 2011

Viruses contain

Either RNA or DNA

viruses are obligate intracellular parasites that contain either DNA or RNA but never both

Viral structures can contain any of the following except:
A. Capsomeres
B. A capsule
C. Viral nucleic acid
D. An envelope
E. A capsid

B. A capsule

This question requires you to know the structures that make up a virion, which are a capsid made up of capsomeres, nucleic acid, and in some cases an envelope. All of these are listed as answers but we are looking for an exception. That makes B the logical and correct choice.

Viral envelopes are formed

When the virus leaves the host cell

Some viruses acquire an envelope as they move out of the host cell during the release phase of the infection cycle. This envelope is made up of the plasma membrane of the host cell.

Bacteriophage are viruses that

Infect bacteria

viruses can be broadly categorized by the type of host cell they infect, be they animal cells, plant cells, or bacterial cells. A bacterial virus is referred to as a bacteriophage

A lytic virus has infected a patient. Describe what is happening inside the patient?

The virus is causing the death of the infected cells in the patient

the lytic cycle the host cell becomes filled with virus and bursts, releasing the new viral particles.

A lysogenic virus

Incorporates its nucleic acid with that of the host chromosome

The lysogenic cycle the viral DNA can insert into the host cell's chromosome. This does not cause lysis of the host cell, and the viral inserted genes are then carried from one generation to the next during cell division.

Imagine you are a virologist studying how a type of virus attaches to its host cells. You have found a virus attachment area on the host cell membrane that seems to be dense and full of fatty acid molecules. This area on the host cell is most likely to be

A lipid raft

The common cold virus (rhinovirus) uses which of the following for attachment?

ICAM molecules

The influenza virus uses which of the following for attachment?


Non-enveloped animal viruses penetrate host cells by:


Enveloped viruses penetrate their host cells by

Fusion of their envelope to the host cell membrane

During the events associated with attachment and penetration, all of the following are true except:
A. Viruses never share host cell receptors
B. Virus-receptor interactions facilitate the infection process
C. Host cell receptors used by viruses represent a large portion of cell membrane proteins
D. For enveloped viruses, fusion occurs between the viral envelope and the host cell membrane
E. Fusion is facilitated by specialized fusion proteins

A. Viruses never share host cell receptors

Animal viruses can have any of the following types of nucleic acids except:
A. Double-stranded RNA
B. Single-stranded RNA
C. Single strands of RNA and DNA
D. Single-stranded DNA
E. Double-stranded DNA

C. Single strands of RNA and DNA

remember that viruses can contain either DNA or RNA but never both

RNA viruses synthesize their nucleic acid in the host cell


recall the structure of the eukaryotic cell, which is the host cell for virus. Recall that whereas DNA is always replicated in the nucleus, RNA synthesis can occur in the cytoplasm.

The enzyme reverse transcriptase

Converts RNA to DNA

In the chapter we talked about retroviruses, which are RNA viruses that can be lysogenic. We saw that for them to insert their genetic information into the host chromosome they had to convert the RNA into DNA. This conversion is accomplished by an enzyme called reverse transcriptase.

Which of the following enzymes is/are involved with the integration of viral DNA into the host chromosome?
A. Reverse transcriptase
B. Integrase
C. Polymerase
D. A only
E. A and B

B. Integrase

In this question you are asked about viral DNA integration, which is the process of integration of viral DNA into the host chromosome. Because it is asking about DNA, the A choice is negated. C is excluded because polymerase is not involved in viral integration. Therefore only choice B is correct.

Construction of viral proteins is performed by:

The host cell's ribosomes

viruses are very simple structures that depend on the host cell for all the processes involved in the production of new virus.

The assembly of virus requires all of the following except:
A. Formation of capsomeres
B. Formation of capsids
C. Formation of viral ribosomes
D. Association of viral genomes with the capsid
E. Coordination of multiple assembly reactions

C. Formation of viral ribosomes

The question concerns viral assembly, and all of the answers relate to that except C. Remember that viruses do not contain ribosomes. They use the host cell's ribosomes. That makes C the exception and the correct answer.

Newly formed virus can be released from the cell by:

Cell lysis and Budding

there are two ways in which virus particles are released from infected host cells. The first is through lysis, in which the host cell essentially explodes. The second form of release is by budding out of the host cell. This process is usually seen in the infection cycle of enveloped viruses.

Viruses can spread through which of the following methods?
A. Fusion of the host cell with a neighbor cell
B. The formation of syncytia
C. The rupture of the host cell
D. All of the above
E. None of the above

D. All of the above

Viral infections can be any of the following except:
A. Slow
B. Latent
C. Acute
D. Temporary
E. Persistent

D. Temporary

Acute infections are represented by:

Rapid production of virus and rapid resolution of infection by host defense

Acute infections are those in which large numbers of virus are produced but the infection is short lived.

A person who is asymptomatic for viral infection

Is infected but shows no symptoms of the infection

The key term here is asymptomatic, meaning showing no symptoms.

Major changes in the structure of the virus are referred to as

Antigenic shift

there are two ways changes in a virus can occur: antigenic drift and antigenic shift. Major changes to viral structure are due to antigenic shift, not antigenic drift,

Cytotoxic T cells can be killed by

Fas molecules on the infected host cell

viruses have the ability to overcome host defenses such as cytotoxic T cells. This defense takes advantage of the Fas molecules found on the surface of infected host cells

Latent infections have all of the following characteristics except:
A. The absence of a productive infection
B. A reduced or absent immune response
C. The viral genome remains intact
D. The presence of a productive infection
E. No large-scale production of virus

The presence of a productive infection

Latent viruses:

Can integrate into the host chromosome

Latent viruses use the lysogenic infection cycle, in which the viral nucleic acid is integrated into the host cell chromosome.

All of the following help to determine viral pathogenesis except:
A. Ability of the infection to kill cells
B. Interactions of the virus with the target cells
C. The host response to the infection
D. B and C
E. None of the above

E. None of the above

there are no exceptions because all of the possible choices help to determine viral pathogenesis.

Which of the following is most important for a successful viral infection?
A. Icosahedral capsids
B. Permissive host cells
C. Viral envelopes
D. Genetic variability
E. None of the above

B. Permissive host cells

When virus is released from the basement membrane of a host cell it will:

Cause a systemic infection

The basement membrane of a cell is found where the cell interacts with other tissues. Therefore virus released across this membrane will invade other tissues. Part of the definition of systemic infection is infection that moves away from the initial focus and into other parts of the body.

Iatrogenic transmission of virus is caused by:

Health care workers

The target site for rabies virus is:

The neuron

Hepatitis is caused by:

Viral infection of the liver and Inflammation of the liver in response to viral infection

Hepatitis is a term used to describe infection or inflammation of the liver. Hepatitis would result from a viral infection. But inflammation of the liver as the result of the host defense against a viral infection is also correct.

Viral shedding is:

Part of the transmission of viral infection

viral shedding is a mechanism that can transmit virus to other people.

Viral vaccines are usually composed of:

Virulent virus and/or Attenuated virus

Viral vaccines can be composed of non-virulent forms of virus or they may be attenuated (treated to inhibit infectiousness), but they can never consist of virulent forms of the virus.

PD50 defines the:

Paralytic dose of a virus

Virulence of a virus can be affected by which of the following?

A. The route of infection
B. The age of the host
C. The sex of the host
D. The ability of the virus to replicate

Koplik spots are seen in:


Koplik spots was one of the initial symptoms that occur of measles infection

The first successfully tested viral vaccine was for:


The vaccine that is most potentially dangerous

Consists of live attenuated virus

Recall that a killed vaccine contains dead pathogens and is therefore not dangerous. Inactivated vaccines are by definition unable to infect, and subunit vaccines are composed of pieces of virus and are therefore non-infectious. Therefore the correct possibility is attenuated. In these vaccines the virus has been modified to lower the infection capability. However, if the treatment is not sufficient the vaccine could contain infectious virus.

All of the following are requirements for an effective vaccine except:
A. The vaccine must be safe
B. The vaccine must be made from killed pathogens
C. The vaccine must induce a protective response
D. The vaccine must be stable
E. The vaccine should be inexpensive if possible

B. The vaccine must be made from killed pathogens

the requirements for a successful vaccine are safety, stability, expense, and protective ability.

Oncogenic viruses:

Cause tumors to develop

the prefix "onco-" can also be seen in the term "oncology," which concerns tumors and malignancies. Oncogenic viruses can cause malignancies.

Protozoan parasites are:


There are two forms of parasitic organism: unicellular and multicellular. The unicellular organisms are referred to protozoan parasites.

Plasmodium falciparum:

Is the most dangerous of the malaria-causing parasites

The malaria infection is caused by Plasmodium species, the most dangerous of which is falciparum.

Which of the following invade the blood and cause chronic illness?
A. Rhizopods
B. Flagellates
C. Ciliates
D. Cestodes


Infection of the blood is usually associated with organisms that have motility.

Protozoan parasites can be all of the following except:
A. Aerobic
B. Facultatively anaerobic
C. Anaerobic
D. Heterotrophic

C. Anaerobic

unlike bacteria, there are no protozoan organisms that live without oxygen.

Sexual reproduction in protozoans is called:


The body of a worm is covered by a:


Nematodes are:


Trematodes are:


The severity of a helminth infection is directly related to:

The number of worms that are present

As in other types of infection such as viral and bacterial, the number of organisms is an indicator of how severe the infection will be.

The organism that causes malaria is transmitted by:

The bite of a mosquito

The intermediate host for Plasmodium species is:

A human

The infection cycle of malaria involves both a definitive and an intermediate host, and humans are the intermediate hosts. It is the mosquito that is the definitive host.

Merozoites of Plasmodium are found in:

Human hepatocytes

the infection with Plasmodium begins when sporozoites found in the saliva of mosquitoes is injected into the human by biting. These sporozoites move to the liver and differentiate into the merozoite form.

All of the following are true about flagellates except:
A. They are widespread in nature
B. They use flagella for locomotion
C. They require an intermediate host for transmission
D. All flagellates cause disease in humans

D. All flagellates cause disease in humans

Enterobius vermicularis is a:


Which system in a parasitic helminth is not greatly reduced compared with free-living helminths?

Reproductive system

parasitic helminths are going to live inside a host. Therefore many of the systems that would be required in the outside world are not required in the host. The only system that is normal in the parasitic worm is the reproductive system.

Transmission of helminthic diseases to humans is usually by:

The gastrointestinal route

When you consider that most worms live in the digestive tract of humans, it makes sense that this system would also be the portal of exit for these organisms.

Cercariae, metacercaria, miracidia, are stages in the life cycle of:


miracidia are the ciliated larvae, cercariae are the tail-bearing larvae, and metacercariae are the maturing encysted larvae.

Which one of the following does not belong with the others?
A. Entamoeba
B. Trypanosoma
C. Cryptosporidium
D. Giardia
E. Plasmodium

C. Cryptosporidium

all of the possibilities are protozoan parasites except C. Cryptosporidium is a fungus and therefore it does not belong with the others.

What do tapeworms eat?

Intestinal contents

Remember that tapeworms are parasites that live in the digestive tract. Therefore they have access to the materials found in the intestinal tract. It is this material that they use as a food source.

Ringworm is caused by a:


Mycology is the study of:


Fungal plasma membranes contain:


fungi are eukaryotic organisms. Unlike prokaryotes, they contain ergosterol in their plasma membranes as a way of strengthening the membrane.

Fungal cell walls contain:

Mannon and Glucan

The branching structures seen in fungi are called:


hyphae are the branching structures seen in the mold form of fungi.

Superficial mycoses:

Are associated with hair shafts

All of the following are true about mucocutaneous candidiasis except:
A. It is caused by Candida albicans
B. It is an infection of the mucous membranes
C. It can be seen as thrush
D. It is a deep mycosis
E. It can be seen as vulvovaginitis

D. It is a deep mycosis

this is an infection of the mucous membranes caused by Candida albicans, which can be seen in the vaginal or oral regions of the body.

Tinea capitis is:

A form of ringworm

generally found on the scalp

Successful host defense against fungal infection:

Is a combination of phagocytosis, the production of antibody, and the T cell response

Recall that both the innate and adaptive immune responses are involved in defeating a fungal infection.

The most commonly seen yeast infections are caused by:

Candida albicans

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