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56 Cards in this Set

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Features of a lysogenic infection
-Viral DNA is incorporated into host DNA (or if the virus has an RNA and the enzyme reverse transcriptase, the DNA is reverse transcribed and then incorporated).
- Virus in this form is known as a temperate virus.
- Virus is said to be dormant or latent while it remains incorporated and may have no effect (known as a provirus or prophage if host is a bacterium)
- Stress may cause dormant virus to become active.
Plus vs Minus strand RNA viruses
Plus-strand indicates that proteins can directly be translated from the RNA. Examples include common cold (unenveloped) and AIDS (enveloped retrovirus)
Minus-strand is the complement to mRNA and must be transcribed to plus-RNA before being translated. Examples include measles, rabies, flu.
Define a retrovirus
Carries the enzyme reverse transriptase in order to create DNA from its RNA.
1. Viroids
2. Prions
1. Viroids are rings of naked RNA without capsids and only infect plants.
2.Naked proteins which cause infections in animals and can reproduce without DNA or RNA.
Define spike proteins
Proteins encoded from viral nucleic acids which protrude from the envelope of the host. These proteins bind to receptors on other host cells causing the virus to be infectious.
Antibodies work by detecting these spike proteins.
Note: these proteins may change since RNA polymerase does not contain a proofreading mechanism.
Key feature of prokaryotes and classification.
Do not have membrane bound nucleus.
Divided into Archae and Bacteria. Archaea have as much in common with eukaryotes as they do with bacteria.
Different sources of carbon.
- Autotrophs are capable of using CO2 as their sole source of carbon (carbon is reduced through an energy expensive process via the calvin cyccle)
Heterotrophs use preformed organic molecules as their source of carbon.
Different sources of energy for prokaryotes.
Phototrops - use light
Chemotrophs - oxidation of orgranic and inorganic matter.
Lithotrophs vs organotrophs
Lithotrophs obtain electrons and hydrogens from inorganic matter, organotrophs do so from organic matter.
Define carbon dioxide fixation
Process by which CO2 is reduced to create organic molecues through a process known as the Calvin cycle.
Define nitrogen fixation
Process by which N2 is converted to ammonia. Is a very enery expensive process.
Features of chemoautotrphy
Very energy expensive. Requires large amounts of substrate. Large environmental impact.
All known chemoautotrophs are prokaryotes.
Features of a virus
Comparable in size to large proteins.
Contains a capsid - protein coat.
Contains either DNA or RNA but not both.
Some viruses may surround themselves with a lipid envelope either borrowed from the host or snythesized using the host cell machinery.
Define virion
A mature virus outside the host cell.
Differences between viruses and living organisms
1. Viruses always require host cell machinery to reproduce.
2. Do not metabolize nutrients - use host ATP.
3. Viruses in active form are not separated from the external environment.
4. Can possess DNA or RNA but never both.
5. Can be crystallized w/o losing ability to infect.
Describe process of viral infection.
1. Virus adsorbs to cell surface by attaching to a receptor on the host membrane (usually a glycoprotein).
2. Nucleic acid penetrates into the cell. In bacteriophage, this usually occurs via the tail. In eukaryotes, by an endocytotic process.
3. Virus infects either through the lytic or lysogenic pathways.
Describe the lytic infection.
Virus commandeers the host machinery and begins to reproduce. Cell may eventually burst (lysis) or release the viruses in a reverse endocytotic process.
Time between infection and production of first virus: eclipse period.
Time before lysis: latent period.
Virus following the lytic cycle is called a virulent virus.
Define plus-strand RNA
RNA from which proteins can be directly translated.
Define minus-strand RNA
RNA which is the complement to mRNA and must be transcribed before translation can occur. Examples include measles.
Define retrovirus
virus which possesses reverse transcriptase which creates DNA from RNA, which is then incorporated into the host.
Other types of viruses
Double stranded RNA viruses, single and double stranded DNA viruses.
Small rings of naked RNA without capsids.
Location of periplasmic space in gram positive and negative bacteria
"Gram +: between plasma membrane and cell wall
External features of bacteria
Capsule(protection), slime layer (can be washed off), fimbraie/pili : not used in motility, used to attach to surfaces; flagella - made of flagellin (different from eukaryotic flagella
Features of flagella
Long, hollow, rigid helical cylinders made from the globular protein called flagelng. They rotate ccw to propel, cw to tumble and change direction. Propelled using proton gradient.
Key difference between prokaryotes and eukaryotes
Prokaryotes do not have a nucleus, eukar. have at least one. Pkyts for the most part have no complex, membrane bound organelles
Nuclear structire of prokaryotes.
- Do not have a nucleus. Instead have a single circular double stranded molecule of DNA. - molecule twisted into supercoils with assoc. histones (archaea) and histone equivalents (bacteria)
Structure formed by prkyt DNA, RNA and protein complex visible under a microscope
Bacterial shapes
cocci, bacilli, spirilla (rigid helical), spirochetes (non-rigid helical)
T/F prkyts have RNA and ribosomes
True - prkyt ribosomes are smaller.
Present in some pkyts in various shapes. Appear as bubbles in microscope. Thought to be involved in cell wall formation during division
Inclusion bodies
Granules of organic or inorg. Matter which may or may not be bound by a mebrane
Main component of plasma membrane
Composed of a phospholipid bilayer. Note: phospholipid is ampiphatic
Micelle formation
Spherical structure formed by ampiphatic mols. in aq. soln. The molecules aggregate with the polar end facing outwards and non-polar end facing inwards.
Vesicle surrounded and filled by aq soln. Formed when critical mass of phospholipids are agitated by UV
Proteins that traverse from inside to outside of cell
Intrinsic/Integral proteins.
Proteins that exist only on one surface
Extrinsic/peripheral proteins.
T/F: membrane lipids and proteins move easily from one leaflet to the other
FALSE since lipid or protein would have to traverse across the non-polar core
Cholesterol present on euk. or pkyt cell membranes?
Euk cells. Pkyt cells have hopanoids insteand which are equivalent to cholesterol
Role of cholesterol on euk. membranes
regulates fluidity
Fluid mosaic model
A model used to conceptualise cell membranes, in it, the membranes are described as a structually and functionally asymmetric lipid bilayer studded with embedded proteins that aid in cross-membrane transport.
Diffusion is caused by:
Brownian motion
Rate of diffusion governed by:
Electro-chemical gradient
Direction of diff.
Direction of greatest entropy
Allowing passage of certain, especially small, molecules or ions but acting as a barrier to others. Degree of permeability governed by both size and polarity
How is water mostly transported to the cell?
Leakage channels. Water transport solely through the bilayer would be too slow. Note: these channels are a consequence of irregularly shaped integral proteins, and are not explicitly designed to transport water.
Features of facilitated diff.
- requires transport proteins - occurs down a conc. Gradient - makes the membrane selectively permeable to certain substances (usually ones that are too large or charged to passively diffuse)
Active transport
Transport of substances against the conc. Gradient with the expense of ATP.
Primary vs secondary active transport
-Primary: ATP breakdown directly causes substance transport Secondary: ATP breakdown establishes the conc. gradient of another substance. Energy in this gradient then harnessed for the active transport.
Plasma membrane of bacterium and everything inside. Usually surrounded by a lipid envelope
What is bacterial cell wall made of?
Peptidoglycan (aka murein) - a series of disaccharide polymer chains w/ amino acids. These chains are connected by amino acid interbridges. It is more elastic and porous than cellulose
Features of gram-positive bacteria
Thich peptidoglycan cell wall absorbs the gram stain and shows up as purple. Have a cell wall 4x thicker than plasma membrane
Features of gram-negative bacteria
Appear pink when stained. Thin peptidoglycan cell wall. Outside the cell wall, bacteria has a lipid bilayer which is more porous than the cell wall. This bilayer has lipopolysaccharides which can form a barrier against antibodies
Location of periplasmic space in gram positive and negative bacteria
Gram +: between plasma membrane and cell wall Gram -: between cell wall and outer bilayer
External features of bacteria
Capsule(protection), slime layer (can be washed off), fimbraie/pili : not used in motility, used to attach to surfaces; flagella - made of flagellin (different from eukaryotic flagella
Features of flagella
Long, hollow, rigid helical cylinders made from the globular protein called flagelng. They rotate ccw to propel, cw to tumble and change direction. Propelled using proton gradient.