University of Illinois Urbana-Champaign MCB 150 Exam 4 |
Questions with 100% Verified Answers | Latest Update
Question:
cost of making the lacZ protein
Answer:
DNA ~3,000 nt transcribed to 3,000 nt mRNA (1 ATP per base = 3,000 ATP) translated to a 1,000 AA
protein (# ATP per AA = 3,000 ATP)
- 6,000 ATP for 1 protein
Question:
rate of translation
Answer:
20 AAs per second 1,000 AAs = 50 sec 6,000 ATP/50 sec = ~120 ATP used per second for one
protein
Question:
glucose
Answer:
preferred energy source in all organisms
Question:
gene regulation
Answer:
turning on and off genes as they are needed in the cell to conserve energy
- adjusts metabolism to achieve maximum growth in a given environment
Question:
constitutive
Answer:
genes that are needed at all times and are not regulated (except in M-phase when transcription
ceases) ex) CDKs
Question:
where can regulation occur
Answer:
transcription initiation, transcript stability, translation initiation, rate of translation, activity of
protein (phosphorylation), and polypeptide stability (protease)
,Question:
where does regulation occur mainlY?
Answer:
at transcription initiation (least amount of ATP is used, but trade off between energy savings and
the speed at which the change takes effect)
Question:
operon
Answer:
multiple protein-coding regions under the control of a single promoter
- transcribed as polycistronic mRNA (essentially the bacterial equivalent of alternative
RNA splicing)
- different regions are independently translated to the different proteins
- each protein-coding region in the mRNA molecule has its own ribosome binding site
and stop codon ex) the lacZ, lacY, and lacA genes all make up th elac operon
Question:
lac operon in E. coli
Answer:
produces beta-galactosidase, galactoside permease, and lac I
Question:
beta-galactosidase
Answer:
- most abundant gene in the lac operon
- amount present varies on the accumulation of lactose in the cell
- breaks lactose down into galactose and glucose
Question:
at what level does the lac operon regulate gene expression?
Answer:
at the transcription initiation stage
Question:
galactoside/lac permease
Answer:
- lac Y
- allows lactose into the cell through the plasma membrane by creating holes in the
membrane for it
,Question:
what regulates the expression of the lac operon?
Answer:
- glucose AND lactose
- glucose is used up first
- once there is no more glucose, a temporarily plateau in cell growth occurs while the
cell reroutes its metabolic pathway
- lactose is then used to obtain glucose, leading to beta-galactosidase accumulating and
cell growth resuming until no more lactose is present
Question:
components of the lac operon
Answer:
Promoter, lac I, Operator, lacZ, lacY, and lacA
Question:
promoter
Answer:
Region where RNA polymerase binds to initiate transcription.
Question:
lac I
Answer:
not part of the operon, codes for the repressor that blocks RNA polymerase and prevents expression
of the lac gene
Question:
operator
Answer:
part of DNA where the lac repressor protein binds to to prevent RNA polymerase from continuing
and transcribing the DNA
Question:
lacA gene
Answer:
transacetylase protein, detoxifies toxic thiogalactosides that are accidentally let into the cell via
lacY
Question:
lactose is also known as
, Answer:
allolactose
Question:
absence of lactose effects on the lac operon
Answer:
lac repressor binds to the operator to prevent RNA polymerase from transcribing the operon
- negative regulation
Question:
presence of lactose on the lac operon
Answer:
lactose bins to the repressor to let go and allow the lac operon to be transcribed by RNA polymerase
Question:
when does maximum transcription of the lac operon occur
Answer:
when no glucose is present but lactose is present
- when glucose is present, lac is transcribed but inefficiently
Question:
positive regulation of lac operon
Answer:
catabolite activator protein (CAP) or cAMP receptor protein (CRP) binds to the lac operon to induce
transcription (binds to the promoter upstream of the operator)
Question:
as the concentration of glucose _____, the concentration of cAMP ______
Answer:
increases; decreases
- glucose inhibits adenylyl cyclase
Question:
how does positive regulation of the lac operon occur
Answer:
cAMP binds to the CRP and the complex binds to the promoter to enhance binding of RNA
polymerase so transcription can occur
- lac operon is a weak promoter
Questions with 100% Verified Answers | Latest Update
Question:
cost of making the lacZ protein
Answer:
DNA ~3,000 nt transcribed to 3,000 nt mRNA (1 ATP per base = 3,000 ATP) translated to a 1,000 AA
protein (# ATP per AA = 3,000 ATP)
- 6,000 ATP for 1 protein
Question:
rate of translation
Answer:
20 AAs per second 1,000 AAs = 50 sec 6,000 ATP/50 sec = ~120 ATP used per second for one
protein
Question:
glucose
Answer:
preferred energy source in all organisms
Question:
gene regulation
Answer:
turning on and off genes as they are needed in the cell to conserve energy
- adjusts metabolism to achieve maximum growth in a given environment
Question:
constitutive
Answer:
genes that are needed at all times and are not regulated (except in M-phase when transcription
ceases) ex) CDKs
Question:
where can regulation occur
Answer:
transcription initiation, transcript stability, translation initiation, rate of translation, activity of
protein (phosphorylation), and polypeptide stability (protease)
,Question:
where does regulation occur mainlY?
Answer:
at transcription initiation (least amount of ATP is used, but trade off between energy savings and
the speed at which the change takes effect)
Question:
operon
Answer:
multiple protein-coding regions under the control of a single promoter
- transcribed as polycistronic mRNA (essentially the bacterial equivalent of alternative
RNA splicing)
- different regions are independently translated to the different proteins
- each protein-coding region in the mRNA molecule has its own ribosome binding site
and stop codon ex) the lacZ, lacY, and lacA genes all make up th elac operon
Question:
lac operon in E. coli
Answer:
produces beta-galactosidase, galactoside permease, and lac I
Question:
beta-galactosidase
Answer:
- most abundant gene in the lac operon
- amount present varies on the accumulation of lactose in the cell
- breaks lactose down into galactose and glucose
Question:
at what level does the lac operon regulate gene expression?
Answer:
at the transcription initiation stage
Question:
galactoside/lac permease
Answer:
- lac Y
- allows lactose into the cell through the plasma membrane by creating holes in the
membrane for it
,Question:
what regulates the expression of the lac operon?
Answer:
- glucose AND lactose
- glucose is used up first
- once there is no more glucose, a temporarily plateau in cell growth occurs while the
cell reroutes its metabolic pathway
- lactose is then used to obtain glucose, leading to beta-galactosidase accumulating and
cell growth resuming until no more lactose is present
Question:
components of the lac operon
Answer:
Promoter, lac I, Operator, lacZ, lacY, and lacA
Question:
promoter
Answer:
Region where RNA polymerase binds to initiate transcription.
Question:
lac I
Answer:
not part of the operon, codes for the repressor that blocks RNA polymerase and prevents expression
of the lac gene
Question:
operator
Answer:
part of DNA where the lac repressor protein binds to to prevent RNA polymerase from continuing
and transcribing the DNA
Question:
lacA gene
Answer:
transacetylase protein, detoxifies toxic thiogalactosides that are accidentally let into the cell via
lacY
Question:
lactose is also known as
, Answer:
allolactose
Question:
absence of lactose effects on the lac operon
Answer:
lac repressor binds to the operator to prevent RNA polymerase from transcribing the operon
- negative regulation
Question:
presence of lactose on the lac operon
Answer:
lactose bins to the repressor to let go and allow the lac operon to be transcribed by RNA polymerase
Question:
when does maximum transcription of the lac operon occur
Answer:
when no glucose is present but lactose is present
- when glucose is present, lac is transcribed but inefficiently
Question:
positive regulation of lac operon
Answer:
catabolite activator protein (CAP) or cAMP receptor protein (CRP) binds to the lac operon to induce
transcription (binds to the promoter upstream of the operator)
Question:
as the concentration of glucose _____, the concentration of cAMP ______
Answer:
increases; decreases
- glucose inhibits adenylyl cyclase
Question:
how does positive regulation of the lac operon occur
Answer:
cAMP binds to the CRP and the complex binds to the promoter to enhance binding of RNA
polymerase so transcription can occur
- lac operon is a weak promoter
