AP Biology : Understanding Viruses and Prions

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Viruses And Prions

Which of these is an example of a disease cause by a prion (misfolded protein)?

Possible Answers:

Tuberculosis

Lupus

Bovine spongiform encephelopathy (mad cow disease) 

HIV

Syphilis

Correct answer:

Bovine spongiform encephelopathy (mad cow disease) 

Explanation:

The only disease out of these that is caused by a prion is mad cow disease, and is therefore the correct answer. HIV is caused by a virus, syphilis and tuberculosis by bacteria, and lupus is an autoimmune disorder.

Example Question #2 : Understanding Viruses And Prions

Human immuodiffiency virus (HIV) contains a special type of enzyme that makes it difficult to classify and develop a vaccine for the virus. The special enzyme of HIV is __________.

Possible Answers:

Luciferase

-ketoglutarase

Lactose dehydrogenase

Reverse transcriptase

Peroxidase

Correct answer:

Reverse transcriptase

Explanation:

Reverse transcriptase is the epitome of viral evolution, as showcased by the HIV virus. Reverse transcriptase enables the HIV virus to create a DNA template from an RNA segment already encapsulated in the virus, but using the host cell's own DNA replication machinery.

Example Question #3 : Understanding Viruses And Prions

Which of these statements is NOT a reason why viruses are not considered to be living?

Possible Answers:

Viruses cannot reproduce independently.

Viruses cannot metabolize nutrients for energy.

Viruses cannot survive outside of a host.

Viruses contain either RNA or DNA; never both.

Correct answer:

Viruses cannot survive outside of a host.

Explanation:

When you think of viruses, think of them as parasites: they prey on host cells and take advantage of their resources. Viruses require the reproductive machinery of host cells in order to reproduce and use the energy in the cells to drive the synthesis processes; however, it is possible for viruses to remain virulent outside of a host for long periods of time. When not infecting a host, viruses are refrred to as virions. Essentially, viruses can survive outside of a host, but cannot replicate.

Example Question #4 : Understanding Viruses And Prions

Why would you never see ribosomes in a virus?

Possible Answers:

Viruses do not use ribosomes when making proteins and have adapted a different method to translate proteins.

Viruses leave their ribosomes outside of the host cell as they have already synthesized all necessary proteins prior to infection.

Viruses do not have any need to create proteins, so ribosomes would be worthless.

Viruses hijack the ribosomes of host cells in order to create the necessary proteins when reproducing.

Correct answer:

Viruses hijack the ribosomes of host cells in order to create the necessary proteins when reproducing.

Explanation:

At no point in the reproductive cycle of a virus does it contain ribosomes. Instead, it uses the ribosomes found in the host cell to synthesize the proteins needed for its reproduction.

Example Question #5 : Understanding Viruses And Prions

Why is it necessary to receive a flu shot every year in order to avoid getting the flu?

Possible Answers:

Influenza destroys the body's antibody reserves and yearly vaccinations are needed to restore antibody levels.

Influenza undergoes genetic mutations throughout the year which allows it to evade previously created cellular defenses.

Your body must be resupplied with fresh antibodies every year in order to maintain immunity to the flu.

Your body must be introduced to influenza yearly in order for your body to continue creating antibodies.

Correct answer:

Influenza undergoes genetic mutations throughout the year which allows it to evade previously created cellular defenses.

Explanation:

Influenza mutates rapidly, and can mutate into a new virus and evade previous vaccines. As a result, new vaccines must be created in order to provide the best defense against the influenza virus for that year. The vaccine you get one year is not going to be the same vaccine you get the next year.

Vaccines allow the body to produce antibodies to the exposed pathogen. They do not provide antibodies.

Example Question #5 : Understanding Viruses And Prions

List the order of major events in the viral multiplication cycle of a lytic bacteriophage.

Possible Answers:

 Endocytosis, replication, assembly, budding, exocytosis

Absorption, penetration, synthesis, assembly, release

Endocytosis, replication, assembly, budding

Adsorption, penetration, synthesis, assembly, release

Adsorption, penetration, synthesis, lysis

Correct answer:

Adsorption, penetration, synthesis, assembly, release

Explanation:

Because the question refers to a bacteriophage, we know that the two answers beginning with endocytosis are incorrect; endocytosis begins the multiplication cycle of an enveloped virus. Bacteriophages are naked viruses, contained within a protein capsule with no outer membrane.

During adsorption, the virus encounters a susceptible bacterial host cell and adsorbs (binds) to receptor sites on the cell membrane like a key fitting into a lock. The flexible cell membrane of the host cell is then penetrated by the viral nucleic acids. During synthesis, the viral nucleic acids take control over the host’s metabolic processes, much like the machinery of a factory assembly line. This causes the host cell to replicate and assemble new viral particles. Once the new viruses are assembled, the host cell ruptures (lyses) and the viruses are released to find new host cells. 

Example Question #6 : Understanding Viruses And Prions

Fever and inflammation are examples of which type of host response to the presence of antigens?

Possible Answers:

Non-specific

Positive chemotaxis

Phagocytosis

Specific

T-cell response

Correct answer:

Non-specific

Explanation:

The non-specific host response includes fever, inflammation, positive chemotaxis, and phagocytosis. These responses are directed at any perceived invader, and therefore are non-specific.

The specific host response targets a specific invader, and includes T-cells, B-cells, and antibodies.

Example Question #3 : Understanding Viruses And Prions

An important identifying difference between eukaryotic and prokaryotic cells is that __________.

Possible Answers:

prokaryotes have flagella; eukaryotes do not

eukaryotes have nuclei

All other answers are correct

prokaryotes are considerably larger and more complex

prokaryotes possess membrane-bound organelles; eukaryotes do not

Correct answer:

eukaryotes have nuclei

Explanation:

Eukaryotic cells have a nuclei; prokaryotic cells have no nuclei.

Eukaryotic cells are considerably larger and more complex. Eukaryotic cells possess membrane-bound organelles; prokaryotic cells, which are smaller and less complex, do not. Both eukaryotic and prokaryotic cells can have flagella, but not necessarily in all cases.

Note that ribosomes are not membrane-bound, and are found in both prokaryotes and eukaryotes.

Example Question #1 : Understanding Viruses And Prions

Viruses are not considered to be "alive" due to all of the following reasons except __________.

Possible Answers:

they do not have cells

they do not contain DNA

they can only reproduce within a host

they do not respond to stimuli

they do not metabolize any kind of food

Correct answer:

they do not contain DNA

Explanation:

Some viruses have a DNA genome, while others use RNA. While DNA may be a crucial component to determining life, it cannot be used to differentiate viruses from living organisms because some viruses do carry their own DNA.

All viruses can be differentiated from living organisms because they do not "eat" or absorb nutrients, they do not have cells, they do not respond to stimuli, and they do not reproduce independently. All living organisms absorb nutrients, have cells, respond to stimuli, and are capable of reproduction, thus making viruses different.

Example Question #8 : Understanding Viruses And Prions

Which of these are structures within cells which contain digestive enzymes to eliminate waste and debris?

Possible Answers:

neutrophils

basophils

natural killer (NK) cells

lysosomes

 

eosinophils

Correct answer:

lysosomes

 

Explanation:

Lysosomes are structures within cells which contain digestive enzymes to eliminate waste and debris.

Neutrophils are the most abundant of the leukocytes making up 40-70% of white blood cells.

Basophils are the least common, representing only about 0.5% of all white blood cells.

Natural killer (NK) cells are lymphocytes, not leukocytes. They compose a small fraction of lymphocytes within the innate immune system.

 

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