Portage Learning: Microbiology Module 6 Already Graded A

Portage Learning: Microbiology Module 6 Already Graded A Can viruses be classified as either prokaryotic or eukaryotic microorganisms? Neither What is an obligate intracellular parasite? Viruses are considered obligate intracellular parasites because they can not replicate on their own. What is a viral capsid? The capsid is a membrane-like protective structure that contains the genetic material, similar to the nucleus of a eukaryotic cell. What is the viral envelope, and what does the presence (or absence) of it tell you about the type of virus? The envelope surrounds the viral capsid, is derived from the host cell membrane and serves as an additional barrier to the external environment. What type of microscope would be used to study the shape of a viral capsid? An electron microscope How does the viral envelope both aid in cell entry as well as hide it from being detected by the immune system? The viral envelope contains the necessary proteins required for interaction with host cells. As the envelope is derived from the host cell membrane, this camouflages the virus and lowers the likelihood of immune detection by making it appear similar to the normal biological host cell. What must happen before viral replication of its genome can occur? For all viruses, the genome is replicated following attachment and entry, never before. Describe the basic steps of the viral life cycle. 1. Attachment: Viral receptors bind to host proteins on the surface of the cell. 2. Entry: The virus fuses with the host membrane and enters the cell 3. Uncoating: (where applicable) the viral capsid disassembles 4. Replication: The viral genome provides the 'blueprint' to make copies of itself 5. Exit: New viruses are produced and leave the cell 6. New infection: Newly produced viruses leave the host cell and go on to infect new cells. The process outlined above now restarts. What is a bacteriophage? A virus that infects bacteria What structural aspects make bacteriophages distinct from viruses that infect either animals or plants? Bacteriophages possess an icosahedral capsid head group and a helical tail. Attached to the tail are fibrous extensions or 'legs' that aid in binding host cells. Which viral replicative process results in the destruction of the host cell? Lytic bacteriophages Describe the appearance of a bacterial culture infected with virus at the time of infection versus later once viral replication is occurring at a high rate. It goes from cloudy to clear To what family of viruses does rubella come from and how is it transmitted? Togaviridae, it is transmitted through airborne particles What is the common name for rubeola, and is it a DNA or RNA virus? Measles are an RNA virus What disease state emerges as a viral reactivation of a prior infection with the varicella virus? Shingles What linear, double-stranded, enveloped DNA virus is the first virus (as of October 26, 1977) to be declared eradicated? Smallpox What are the two key glycoproteins found in the influenza virus? HA and N Describe the composition of HIV. HIV contains two copies of single-stranded, linear RNA that is enclosed by a capsid. The conical capsid surrounds the two RNA strands and is comprised of ~2,000 copies of the viral protein p24. A viral envelope derived from the cell host membrane then surrounds the viral capsid. Within this envelope are two key glycoproteins, gp120 and gp41, which are essential for viral binding and entry into the host cell.