Micro Unit 4, lecture 2

List 4 shapes of viruses:

1. Helical viruses- a virus consisting of nucleic acid surrounded by a hollow protein cylinder or capsid and possessing a helical structure 2. Polyhedral viruses- consist of a nucleic acid surrounded by a polyhedral (many sided) shell or capsid, usually in the form of an icosahedron 3. Enveloped viruses- consist of nucleic acid surrounded by either a helical or polyhedral core and covered by an envelope 4. Binal viruses- have neither helical or polyhedral forms, are pleomorphic or irregular shaped or have complex structures

State 2 living characteristics of viruses:

1. The reproduce at a fantasic rate, but only in living host cells 2. They can mutate

List 3 criteria used to define a virus:

1. The vast majority of virues contain only one type of nucleic acid: DNA or RNA but not both 2. Viruses are totally dependent on a host cell for replication 3. Viral components must assemble into complete viruses to go from one host cell to another

State 2 non living characteristics of viruses:

1. They are acellular, contain no cytoplasm or organelles 2. They carry out no metabolism on their own and must replicate using the host cells metabolic machinery. Viruses do not grow and divide

A virus must make an RNA copy of its DNA genome. What enzyme would it use?

A DNA dependent RNA polymerase

A retrovirus needs to make a DNA copy of its RNA genome. What enzyme would it use?

A RNA dependent DNA polymerase

A hollow protein shell surrounding a viral genome and usually composed of protein subunits called capsomeres is called:

A capsid

The protein shell that encloses the nucleic acid of a virus is called what?

A capsid

Which of the following could a virus have as a genome?

A double stranded DNA or RNA A single stranded DNA or RNA

A virus lacking an envelope is called what?

A naked virus

What best describes a virus?

Acellular

refers to antigen specific defense mechanisms that take several days to become protective and are designed to react with and remove a specific antigen. This is the immunity one develops throughout life.

Adaptive (acquired) immunity

is defined as a molecular shape that reacts with antibody molecules and with antigen receptors on lymphocytes. We recognize those molecular shapes as foreign or different from our body's molecular shapes because they fit specific antigen receptors on our B-lymphocytestext annotation indicatortext annotation indicator and T-lymphocytestext annotation indicatortext annotation indicator, the cells that carry out adaptive immunity.

Antigen

The protein subunits forming a viral capsid:

Capsomere

The single protein subunits that form the shell surrounding the viral genome is called what?

Capsomeres

This immunity involves the production of cytotoxic T-lymphocytestext annotation indicatortext annotation indicator, activated macrophagestext annotation indicatortext annotation indicator, activated NK cellstext annotation indicator, and cytokinestext annotation indicatortext annotation indicator in response to an antigen and is mediated by T-lymphocytes. These defense cells help to remove infected cells and cancer cells displaying foreign epitopes. Virus-infected host cells naturally bind viral epitopes to a host molecule called MHC-Itext annotation indicator and place the MHC-1 with bound viral epitope on the surface of the infected cell (see Fig. 2) where they can be recognized by CTLs having a T-cell receptors on its surface with a complementary shape.

Cell mediated immunity

Regarding the naming of enzymes involved in the replication of viral nucleic acid, state what the "dependent" part of the name refers to and what the "polymerase" part of the name refers to:

Dependent part of the name refers to what type of nucleic acid is being copied Polymerase part of the name refers to what type of nucleic acid is being synthesized

Describe how most animal viruses obtain their envelope:

Derived from host cell Membranes by a process called budding. The envelope may come from the host cells nuclear membrane, vacuolar membranes, or outer cytoplasmic membrane

Most viruses get their ___ from host cell membranes by budding

Envelopes

The actual portions or fragments of an antigen that react with antibodies and with receptors on B-lymphocytes and T-lymphocytes are called

Epitopes

This immunity involves the production of antibodytext annotation indicatortext annotation indicator molecules in response to an antigen and is mediated by B-lymphocytes. Through a variety of mechanisms, these antibodies are able to remove or neutralize microorganisms and their toxins after binding to their epitopes. For example, antibodies made against viral surface antigens can prevent viruses from adsorbing to host cell receptors thus blocking viral replication or function as opsonizing antibodies to attach viruses to phagocytes for enhanced attachment.

Humoral immunity

an antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any microbe. This is the immunity one is born with and is the initial response by the body to eliminate microbes and prevent infection.

Innate immunity

NK cells use the ______ on their surface to bind to ___ on infected cells and tumor cells

Killer activating receptors; stress glycoproteins

State why some bacteriophages are more complex than typical polyhedral or helical viruses:

More complex than typical nucelocapsid or enveloped viruses and may posses a unique tail structure composed of a base plate, tail fibers, and a contractile sheath

Infectious protein particles responsible for a group of transmissible and/or inherited neurodegenerative diseases such as Creutzfeldt-Jakob disease, kuru, and Gerstmann-Straussler-syndrome

Prion disease

CTLs use the _____ on their surface to bind to _____ on infected cells and tumor cells

TCRs and CD8 molecules; MHC-1 molecules with bound peptide epitopes from viral antigens

The primary cytokines produced in response to viral PAMPS binding to host cell PRRs are called what?

Type 1 interferons

An intact, infectious viral particle is called a ____ and consisit of:

Virion Consist of: 1. A genome 2. A capsid 3. An envelope

They are small, circular, single stranded molecules of infectious RNA lacking even a protein coat. They are the cause of a few plant diseases such as potato spindle-tuber disease, cucumber pale fruit, citrus Exocet is disease and cadang-cadang

Viroids

Acellular, carry out no metabolism on their own, the vast majority possesses either DNA or RNA but not both. This best describes?

Viruses

Compare the size of most viruses to that of bacteria:

Viruses are much smaller with the vast majority being submicroscopic. Most range 5-300 nanometers Viruses are not cells therefore dont need to carry their own cytoplasm or organelles Viruses use the host cells metabolic machinery to replicate

Why cant viruses replicate on environmental surfaces or in synthetic laboratory medium?

Viruses have no cytoplasm or cellular organelles

Define bacteriophage:

Viruses that only infect bacteria