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BIO 2051 EXAM 2024 with Questions Solved 100% Correct | Verified Answers
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BIO 2051 EXAM 2024 with Questions Solved 100% Correct | Verified Answers
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BIO 2051 EXAM 2024 with Questions Solved 100%Correct | Verified Answers
DNA binding domain - ✔✔often homodimeric, posses domain that binds to one inverted
repeat, contain helix-turn-helix domain, and both lac and trp repressors of E.Coli
proteins that control the rate of transcription by binding to specific DNA - ✔✔transcription
factors
turns on transcription, binds DNA and recruits RNA polymerase or sigma factor to promoter
region - ✔✔activator protein
turns off expression, binds operator region of DNA downstream of promoter - ✔✔repressor
protein
small molecules that control binding of activators and repressors, typically cell metabolites or
structural analogs: tryptophane and lactose - ✔✔effectors
conformation altered when effector molecule binds to it - ✔✔allosteric proteins
several structural genes (code for important enzymes from the same metabolic pathway) that
are regulated by the same promoter and operator (regulatory) DNA sequences. - ✔✔operon
is a sequence recognized by the RNA polymerase, operator sequence codes for a repressor
protein. - ✔✔promoter
usually stay turned OFF until a substrate becomes present . They encode enzymes of the
catabolic pathway (lactose operon is an example that encodes enzymes that degrade lactose). -
✔✔inducible operon
,usually stay ON, until the product accumulates in sufficient quantities. The repressor protein is
NOT engaged, the RNA polymerase is able to transcribe the operon and ribosomes make the
enzymes, and enzymes participate in metabolic pathway (it is anabolic pathway, for example,
arginine synthetic pathway is such an operon). - ✔✔repressible operon
regulator protein facilities transcription - ✔✔positive control
operons vs regulons - ✔✔each operon has an activator-binding site.
regulons also exist for negatively controlled systems
include sensor kinase, it get autophosphorylated, than transfer this phosphoryl group to a
response regulator which binds to DNA and induces or blocks transcription of certain genes) -
✔✔two component mechanism
example: osmotic pressure response - ✔✔two component mechanism example
regulation of chemotaxis (run and tumble motion toward attractants or away from repellants).
Bacteria use it to sense temporal changes in concentration of attractants/repellents, and
regulate flagellar rotation: This regulates existing proteins, instead of transcription of new
proteins. - ✔✔modified two component systems
chemical (from the environment) ->MCPs-> sensor kinase (CheA) and CheW-> CheY(response
regulator)->control of flagellar rotation. - ✔✔chemotaxis signal transduction path
governs direction of rotation of flagella - ✔✔Che Y
When M C P s bind attractant, unphosphorylated Che Y _______________ bind to flagellar
motor, resulting in counterclockwise rotation and running - ✔✔does not
, regulatory mechanism by which bacteria and some archaea assess their population density -
✔✔quorum sensing
ensures many cells are present before initiating certain activity. The autoinducer is produced,
secreted outside cells, then it reaches threshold concentration and diffuses back into cells,
binds to activator protein, which triggers transcription of genes (like Lux operon controlling
bioluminescence) - ✔✔quorum sensing
lactose operon and maltose regulon respond to a higher level regulatory mechanisms, called -
✔✔global controls
controls use of carbon sources if more than one present, glucose always used first. also called
"glucose effect" - ✔✔catabolic repression
if shifted from amino acid access to limitation, rRNA and tRNA synthesis stops and no new
ribosomes are produced - ✔✔stringent response
activated in survival situations. Mechanism: If shifted from amino acid excess to limitation, r R N
A and t R N A synthesis stops and no new ribosomes produced
Protein and D N A synthesis stop, new amino acids biosynthesized
Later, r R N A synthesis and new ribosome production begin again at a slower rate
Triggered by two regulatory nucleotides/alarmones - ✔✔stringent response
One Example: E coli, triggered upon nutrient depletion - ✔✔stringent response
global control mechanism to protect cells from protein denaturation resulting from heat, high
solvent levels, osmotic stress, ultraviolet light - ✔✔heat shock response
helper proteins, counteract damage of denatured proteins and help cell recover from stress -
✔✔heat shock proteins
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