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Micro Lecture Exam 2 Handout 8 & 9

Terms in this set (77)

Obligatory intracellular parasites
-contain DNA or RNA
-contain a protein coat
-some are enclosed by an envelope
-some viruses have spikes
-most viruses infect only specific types of cells in one host
Host range
is determined by specific host attachment sites and cellular factors
virion structure
nucleic acid:
-DNA or RNA
-single strand or double strand
-SS RNA, DS RNA, SS DNA, DS DNA
-linear or circular
-segmented in influenze virus
virion structure (capsid)
capsid
-made of capsomerers
-protects core (nucleic acid) from nuclease enzyme
-vehicle of transmission
-used for attachment
-immunogenic (host make anti body against it)
virus envelop structure
1.made of lipids, proteins, and carbs
2. some viruses bud from cell and take plasma membrane as envelope
3. some times covered by spikes (projections made of carb-protein)
virus spike
can be used for:
attachment, identification, hemagglutination
complex virus
-bacteriophage
-poxvirus(no identified capsid but several coats)
orthopoxvirus
The Lytic Cycle
1. Attachment
2. penetration
3. biosynthesis
4. maturation
5. release
The lytic cycle attachment
phage attaches by tail fibers to host cell
The lytic cycle penetration
phage lysozyme opens cell wall; tail sheath contracts to force tail core and DNA into cell
The lytic cycle biosynthesis
production of phage DNA and proteins
The lytic cycle maturation
assembly of phage particles
The lytic cycle release
phage lysozyme breaks cell wall
Lytic cycle of a T-even bacteriophage
The Lysogenic Cycle
1. Called lysogenic or temperate phages
2. do not cause lysis and cell death unless proceed to lytic cycle
3. capable of incorporate their DNA into the host cell's DNA
4. inserted phage DNA called prophage
5. prophage remains latent
6. two repressor proteins(produce by phage genes) turn off phage genes expression
7. when bacterial DNA replicates, prophage DNA replicate also
8. UV or certain chemicals can lead to excision of the phage and including the lytic cycle
Lytic Cycle results
-phage causes lysis and death of host cell
lysogenic cycle results
-prophage DNA incorporated in host DNA
-phage conversion
-specialized transduction
Results of lysogeny
1. lysogenic cells are immune to infect by the same phage again
2. phage conversion
3. specialized transduction
phage conversion
Host cell may exhibit new properties. Like following encoded genes by prophage:
I. Toxin gene in Corynebacterium diphtheriae
II. Streptococci carry the prophage, cause toxic shock
syndrome
III. Toxin gene in clostridium botulinum IV. Shiga toxin gene in E. coli O157H7
specialized transduction
packing special bacterial genes by phage
generalized transduction
multiplication of animal viruses
-attachment
-penetration
-UNCOATING- by viral or host enzymes
-biosynthesis
-maturation
-release
multiplication of DNA virus
*DNA goes inside nucleus
prions
-proteinaceous infectious particle
-inherited and transmissible by ingestion, transplant, and surgical instruments
-spongiform encephalopathies
-PrPc: normal cellular prion protein, on cell surface
-PrPSc: scrapie protein; accumulates in brain cells, forming plaques
1 glucose
produces 38 ATP
reverse transcriptase
-copies viral RNA to produce double-stranded DNA
oncogenic DNA viruses
-adenoviridae
-herpesviridae (EBV causes Burkitt's lymphoma)
-poxviridae
-papovaviridae (papiloma virus causes cervical cancer)
-hepadnaviridae (HBV causes hepatic cancer
oncogenic RNA viruses
-Retroviridae (adult T-cell leukemia and lymphoma)
1. viral RNA is transcribed to DNA which can integrate into host DNA
2. HTLV-1
3. HTLV-2
RNA virus
2 kinds
-positive-sense viral RNA
-Negative-sense viral RNA
1 difference in RNA virus is it does not go in the nucleus, it stays in cytoplasm
negative-sense viral RNA
is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA polymerase before translation
characteristics of enzymes
...
ATP generation
-ATP is generation by the phosphorylation of ADP
-Energy from the transfer of a high- energy PO4- to ADP generates to ATP
-Adenosine-P~P(ADP)+Energy+P => ATP
-substrate level phosphorylation
The Krebs Cycle
CO2 is produced
1 glucose produces
2 pyruvic acid
catalyst
substances that can speed up a chemical reaction without being permanently altered
enzymes
-biological catalysts
-specific for a chemical reaction not used up in that reaction
apoenzyme
protein component
cofactor
nonprotein component
-coenzyme: organic cofactor
holoenzyme
apoenzyme plus cofactor
components of a holoenzyme
apoenzyme + cofactor (coenzyme) => holoenzyme
important coenzymes
NAP+, NADP+. FAD, Coenzyme A
the mechanism of enzymatic action
lyase (enzymes)
removal of enzymes without hydrolysis
isomerase (enzymes)
rearrangement of atoms
ligase (enzymes)
joining of molecules, uses ATP
factors influencing enzyme activity
temp, pH, substrate concentration, inhibitors
denatured proteins
temp and pH denature proteins
enzymatic activity increases with
increasing temp, until the enzyme is denatured and inactivated, then the rate falls steeply
increasing concentration of substrate molecules
the rate of reaction increases until active sites are filled
enzyme inhibitors
using inhibitors is an effective way to control the growth of bacteria
competitive inhibition
-sulfa drugs compete with PABA
-stop production of folic acid in bacteria
-kills bacteria
noncompetitive inhibition
-do not compete with substrate
-attach to allosteric site of enzyme
-change in active site's shape
-Cyanide and fluoride
feedback inhibition
end product inhibits the enzyme
metabolic pathways of energy production
glycolysis
-the oxidation of glucose to pyretic acid produces ATP and NADH
-2 ATP used
-1 glucose=> 2 pyretic acid
-4 ATP produced, 2 NADH produced
alternatives to glycolysis
-pentose phosphate pathway (nucleic acids, certain amino acids, glucose from CO2 in photosynthesis)
-Entner-Doudoroff pathway (produces NADPH and ATP, does not involve glycolysis)
cellular respiration
after glucose produces 2 pyretic acids, they can be channeled into fermentation or oxidation (respiration)
The Krebs Cycle
-pyruvic acid can not enter Krebs cycle directly
-must go through a process called decarboxylation
-oxidaiton of acetyl CoA produces NADH and FADH2
the electron transport chain
a series of carrier molecules that are, in turn, oxidized and passed down the chain
-energy released can be used to produce ATP by chemiosmosis
chemiosmosis
mechanism of ATP synthesis using the electron transport chain
aerobic respiration
yields more energy
end products of fermentation
biochemical tests
used to identify bacteria
catabolism
provides energy and building blocks for anabolism
anabolism
uses energy and building blocks to build large molecules
metabolic pathway
a sequence of enigmatically catalyzed chemical reactions in a cell
-determined by enzymes
enzymes are encoded by
genes
role of atp in coupling reactions
activation energy with the enzyme is
less than the activation energy without the enzyme
RNA viruses can be further classified according to
the sense or polarity of their RNA into neg sense and pos sense.
-pos sense is similar to mRNA and thus can by immediately translate
-neg sense is complementary to mRNA and needs to be converted to pos sense
RNA + strand
viral RNA functions as a template for synthesis of RNA polymerase which copies - strand RNA to make mRNA in cytoplasm
RNA, - strand
viral enzyme copies viral RNA to make mRNA in cytoplasm
RNA double-stranded
viral enzyme copies - strand RNA to make mRNA in cytoplasm
RNA, reverse transcriptase
viral enzyme copies viral RNA to make DNA in cytoplasm; DNA moves to nucleus
viroids
short pieces of naked RNA (300-400 nucleotides)
-3D
-protected from cellular enzymes
-plant pathogens only
latent viral infections
-virus remains in equilibrium with the host
-virus remains asymptomatic host cell for long periods
-will be activated by immunosuppresion
1. cold sores (HSV)
2. Shingles (varicellovirus)
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