Deck 4: Virus Entry

Question 1

Most viruses must exit the endosome before it fuses with a lysosome.Why?

A)Their envelope will not fuse easily with the lysosomal membrane.
B)To avoid the very low pH in the lysosome,which causes destructive conformational changes.
C)To avoid being degraded by lysosomal proteases and nucleases.
D)To enhance their movement towards the nucleus of the cell.
E)The pH of the lysosome is too high to induce membrane fusion.

Answer 1

C

Question 2

Adenoviruses use which of the following entry mechanisms?

A)The fibers on the virion can penetrate the endosome membrane can cause it to lyse open.
B)An interaction between the penton base of the virus and the cellular integrin proteins causes the endosome membrane to lyse open
C)The capsid forms a pore through the cell membrane and extrudes the genome into the cytoplasm
D)The viral envelope fuses at the plasma membrane after binding to the host integrin protein.
E)The viral envelope fuses with the nuclear membrane after binding to the nuclear pore complex.

Answer 2

B

Question 3

Many large DNA viruses use which of the following cellular components to get their nucleocapsid near to the host cell nucleus

A)intermediate filaments
B)nuclear pore complex
C)actin filaments
D)microtubules
E)importins

Answer 3

D

Question 4

The interaction between the viral particle and the host cell receptor is a major determinant of the species specificity of viral infections.

Question 5

Most DNA viruses replicate in the cytoplasm of the host cell,since the ribosomes they need to translate their mRNAs are located in this cellular compartment.

Question 6

The major different between class I fusion proteins and class II fusion proteins is that ….

A)class I protein mediate fusion at the plasma membrane and class II protein mediate fusion with the endosome membranes.
B)only class I proteins contain fusion peptides.
C)only class II proteins have a transmembrane domain.
D)only class I proteins undergo large conformation changes within the protein during entry.
E)class I proteins are found in unenveloped virus particles while class II proteins are found in enveloped particles.

Question 7

Orthymyxoviruses and paramyxoviruses both bind to which receptor on the surface of which host cells?

A)an immunoglobulin family receptor protein
B)the CD4 protein
C)the carbohydrate sialic acid
D)the neuraminidase enzyme
E)a multiple membrane spanning transport protein

Question 8

Because of the rigid plant cell wall,the entry of plant viruses is difficult.Which of the following is a description of how plant viruses move between individual cells within in a whole plant?

A)They move between cells using plasmodesmata.
B)They cause the formation of syncytia.
C)They use the receptor mediated endocytosis pathway.
D)They rely on insect vectors to transfer virions between the cells in a single host.
E)They produce movement proteins that can create holes in the plant cell wall,allowing movement of the virions between cells.

Question 9

Which of the following is the best description of a syncytia?

A)A cellular structure that viruses us to move within a host cell.
B)A fusion of two cells causes by viral envelope glycoproteins.
C)A structure between two plant cells that viruses can use for cell to cell movement.
D)A vesicle involved in the receptor mediated endocytosis pathway.
E)A protein that is involved in the transport of proteins into the nucleus.

Question 10

Which of the following is an example of a virus that requires two different host cell receptors to complete its entry into the host cell?

A)HIV-1
B)Adenovirus
C)Polio (picornavirus)
D)Influenza virus (orthomyxovirus)
E)Both HIV an Adenovirus require two cell receptors for entry.

Question 11

Inhibition of the M2 protein of influenza with the drug amantadine will block which step of virus entry?

A)fusion of the viral envelope with the endosome membrane.
B)movement of the RNA genome segments through the nuclear pore
C)the conformational change that the HA proteins exhibit in response to the drop in pH
D)binding to sialic acid on the surface of the host cell
E)unpacking of the viral RNA genome segments from the virion

Question 12

What mechanism do most retroviruses,but not HIV,use to get their genome into the host cell nucleus?

A)They actively inject their genome into the nucleus through the nuclear pore complex.
B)These viruses do not need to enter the nucleus to replicate.
C)They attach their genome to importin proteins which carry them into the nucleus.
D)They wait until the cell enters mitosis and the nuclear envelope breaks down.
E)The genome is bound to viral proteins that contain nuclear localization signals that move the genome through the nuclear pore complex.

Question 13

Which of the following is an accurate description of cavelolae?

A)Small,flask-shaped invaginations of the plasma membrane enriched in cholesterol.
B)Vesicles surrounded by a cage of clatherin proteins.
C)Regions of the plasma membrane rich in cell signaling molecules.
D)A cytoskeletal network that is involved in transport of vesicles to the nucleus.
E)A cellular motor protein that is involved in intracellular transport.

Question 14

As part of an experiment,you take a solution of purified influenza virus particles and lower the pH of the solution to 5.5.You then add the virus to a culture of the appropriate host cell.What do you think would happen?

A)The HA protein would become inactivated and the virus would not be able to enter the host cell.
B)The viral genome would be degraded and the virus would not be able to start the infection.
C)The HA protein would be able to bind more tightly to the host cell receptors.
D)The cell would not be able to take up the virus particles into clatherin coated pits.
E)The virus particles would not be able to be transported into the nucleus.

Question 15

Before the viral genome can be transcribed or replicated in a new host cell it must….

A)be trimmed by cellular nucleases.
B)be transported through the receptor mediated endocytosis pathway.
C)be processed through the cellular exocytosis pathway.
D)enter the host cell nucleus and be bound by cellular histone proteins.
E)be uncoated in the appropriate compartment of the correct cell type.

Question 16

Which of the following organelles is used as a sorting and recycling station in the receptor mediated endocytosis pathway?

A)Early endosome.
B)Clatherin-coated vesicle.
C)Lysosome.
D)Golgi apparatus.
E)Caveolae

Question 17

Unenveloped viruses must get their genome past the hydrophobic cell membrane.Some accomplish this by doing which of the following?

A)They cause the plasma membrane to lyse.
B)They insert viral proteins into a vesicle membrane.
C)They inject their genome into the nucleus via the nuclear pore complex
D)They create a pore through the membrane and extrude the genome directly into the cytoplasm
E)They create a clatherin coated pit during entry

Question 18

A soluble form of the CD4 protein was once investigated as a treatment for HIV infection.How would this protein work to block infection.

A)It would raise the pH of the endosome and prevent activation of the fusion protein.
B)It would bind to the cell membrane and prevent fusion of the HIV virion with the plasma membrane.
C)It would interact with the host cell receptor and prevent binding by the virion glycoproetin.
D)It would interact with the HIV envelope glycoprotein and block its interaction with the host cell receptor.
E)It would inhibit entry of the viral genome into the cell nucleus.

Question 19

Which of the following describes the function of dynein?

A)It is a protein involved in importing cargo into the nucleus through the nuclear pore complex.
B)It is a motor protein that moves along microtubules towards the nucleus.
C)It is a motor protein that moves along microtubules towards the cell periphery.
D)It is a cell structure used to pass virus particles directly between host cells.
E)It a cellular membrane protein used as a cell receptor by many viruses.

Question 20

Which of the following statements is a good explanation for the observation that many different rhinovirus strains can all use the same host cell receptor?

A)The receptor binding site is buried at the base of a narrow canyon on the viral capsid which is inaccessible to antibody proteins.
B)The recptor binding site is the most exposed area of the capsid which is highly accessible to antibody proteins.
C)The amino acid sequence of the canyon region of the capsid is highly variable.
D)The amino acid sequence on the antibody exposed surfaces of the capsid is highly variable.
E)The amino acid sequence on the exposed areas of the capsid are highly conserved in each strain.

Question 21

The diameter of the opening in the nuclear pore complex is much too narrow to allow passage of any virus particles directly into the nucleus.

Question 22

Describe what a fusion peptide is and how it is involved in mediating membrane fusion between the viral envelope and the cell membrane?

Question 23

It would be correct to say that in a topological sense the nucleocapsid of an enveloped virion has never left the cytoplasm of a host cell.

Question 24

Enveloped viral particles require activation energy in order to penetrate the host cell.Describe the two events that these viruses can use to provide this activation energy.