Microbiology Exam 2 Questions with 100% Complete Solutions, A+

Are Viruses Living or Nonliving? - They are only considered living when they are inside of a host cell, using their resources and energy. Outside of a host they are considered intert. When are Viruses considered to be "alive"? - When they are inside of a host cell. When inside, their nucleic acid (ONLY RNA OR DNA) become active. *Virus replicates Obligatory Intracellular Parasites - Require livinghost cell in order to multiply - Such as Viruses. Defining a Virus - 1) Contains 1 Nucleic Acid (DNA or RNA) 2) Protein coat surrounds the DNA or RNA 3)Multiply within host using host machinery ---because they don't have the ways of making/obtaining their own nutrients. like ATP or enzymes. Virus Characteristics - *Some are enclosed by an envelope which consists of lipids, proteins, carbohydrates *some have spikes *only infect the cells of ONE host. Host Range - The spectrum of host cells that a virus can infect. -invertebrates -vertebrates -plants -protist -fungi -bacteria The virus must be able to attach to a the particular host's cell. **Host range is determined b specific attachment sites on the host cell's surface Bacteriophages - Bacteria that is infected by a virus How do Viruses attach to a host cell - Through receptors on the host cell's surface. There must be an interaction. Capsid - Protein coat that surrounds the Nucleic Acid of a virus. (not the whole virus itself. That's an envelope.) ****Made up of individualized Capsomeres**** *accounts for most of the mass of a viral cell. Capsomeres - Protein subunits that make up a capsid (think of tiny balls that come together to make a huge coating around the Nucleic Acid) *capsomeres can be made up of multiple types of proteins or one single type of protein Envelope - Surrounds the virus as a whole. *Synonymus to a somatic cell's Plasma Membrane. But around a virus. ***Composed of proteins, lipids and carbs. *Could be covered in spikes NOT ALL VIRUSES HAVE ENVELOPES Spikes - Cover the envelope of the cell Composed of protein and carbohydrates. -Used for attachment to the host cell Spikes differ, and can be identified as different virus by the host body. That's why you can get the flu more than once a year, there's a change in spikes. -Can be used for identification for some virsus under microscope. Helical Capsid - Long rods that are flexible and rigid These surround the Nucleic Acid. *Capsids are hollow cylinders surrounding the nucleic acid. *CAN OR CANNOT HAVE A ENVELOPE. Without envelope = they look like long noodles, because it's just the capsid and no sphereical shape WITH the envelope = they look like balls, but with their Nucleic acids all tangled inside. Polyhedrical Capsid - These are icosahedron, and are 20 triangle shapes, with 12 corners. THEY CAN BE WITH OR WITHOUT ENVELOPE -Without envelope, you can see their individual caposomere and their many different triangular faces of the Capsid WITH envelope, they appear ordinarily spherical, and like a normal cell. (Some have spikes) Complex Capsid - They have a variety of weird shapes within the one virus cell, and look just straight up weird.