Micro 261 Chapter 6

________ pathways typically rely on ________ proteins to inhibit mRNA synthesis. A) Anabolic; repressor B) Catabolic; repressor C) Anabolic; activator D) Catabolic; activator

A) Anabolic; repressor

Which statement is TRUE of two separate regulators controlling one individual operon? A) The two regulators themselves must respond to different signals, which enables both to control the operon differently. B) One regulator will likely control the transcription of one section of the operon, whereas the other regulator will control the other component. C) One regulator will bind to the operator region whereas the other will bind to the promoter region so they can co-occur and co-regulate the operon. D) Two regulators trying to control the same operon will likely result in only one being maintained after several generations.

A) The two regulators themselves must respond to different signals, which enables both to control the operon differently.

Cyclic AMP is synthesized from ATP by an enzyme called ________ which is involved in ________. A) adenylate cyclase / catabolite repression B) adenylate cyclase / transcriptional activation C) cAMP receptor protein (CRP) synthase / catabolite repression D) cAMP receptor protein (CRP) synthase / transcriptional activation

A) adenylate cyclase / catabolite repression

Global regulatory systems include all of the following EXCEPT A) amino acid synthesis. B) transformation. C) heat shock response. D) anaerobic respiration.

A) amino acid synthesis.

Which regulatory mechanism does NOT depend on a conformational change in protein/enzyme structure to change activity? A) attenuation B) catabolite repression C) feedback inhibition D) negative control

A) attenuation

Transcriptional control in Archaea most closely resembles that in ________ and utilizes ________. A) bacteria; regulatory proteins B) eukaryotes; regulatory proteins C) bacteria; transcription factors D) eukaryotes; transcription factors

A) bacteria; regulatory proteins

The most frequent way in which small regulatory RNA molecules exert their effects is by A) base pairing with other RNA molecules that have regions of complementary sequence. B) binding to a repressor and repressing enzyme transcription. C) acting as an inducer that then binds to an activator protein to allow transcription to proceed. D) signal transduction.

A) base pairing with other RNA molecules that have regions of complementary sequence.

In Bacteria, sensor kinases that respond to extracellular signals transfer this signal to the cytoplasmic machinery by typically phosphorylating the residues. A) histidine B) serine C) threonine D) tyrosine

A) histidine

Transcriptional regulators bind most frequently at the ________ site of DNA. A) major groove B) minor groove C) histone complex D) primary supercoil

A) major groove

When more than one operon is under the control of a single regulatory protein, the operons are collectively called a(n) A) regulon. B) operator. C) autoinducer. D) riboswitch.

A) regulon.

Enzyme induction occurs A) when the substrate is present. B) when the organism is environmentally stressed. C) continuously. D) when the substrate is depleted.

A) when the substrate is present.

Which is NOT true regarding transcriptional controls in Archaea? A. Like Eukarya, they use several transcription factors to interact with RNA polymerase. B. Their control mechanisms more closely resemble those of Bacteria than Eukarya. C. Archaeal repressor proteins block the binding of RNA polymerase or of TBP and TFB. D. Archaeal activator proteins recruit TBP to the promoter.

A. Like Eukarya, they use several transcription factors to interact with RNA polymerase.

In positive control regulation, the activator protein binds to the ________ site to induce transcription. A. activator-binding B. operator C. promoter D. repressor

A. activator-binding

Whereas gram-negative bacteria such as the Proteobacteria often use ________ as autoinducers, quorum-sensing gram-positives more commonly use ________ that act as autoinducers. A. acyl homoserine lactones / short peptides B. acyl homoserine lactones / quinones C. short peptides / acyl homoserine lactones D. quinones / acyl homoserine lactones

A. acyl homoserine lactones / short peptides

The differentiating mechanism between a flagellar response to a chemoattractant or a chemorepellent involves the ________ activity being low or high (respectively) on ________. A. autophosphorylation / CheA B. autophosphorylation / MCPs C. demethylation / CheA D. demethylation / MCPs

A. autophosphorylation / CheA

Where do transcriptional regulators most commonly bind to? A. major grooves in dsDNA B. minor grooves in dsDNA C. primary supercoils D. promoter sequences

A. major grooves in dsDNA

When arginine is added to a culture already growing exponentially in a medium without arginine, what occurs? A) All cellular growth ceases. B) Growth continues, but the production of enzymes required for the synthesis of arginine ceases. C) Growth continues, but the production of enzymes required for the synthesis of arginine increases. D) The cell returns to the lag stage of growth to synthesize the proteins necessary for the metabolism of arginine.

B) Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

Infection by the foodborne pathogen E coli O157:H7 involves all of the following host and pathogen signaling molecules EXCEPT A) AI-3. B) MCP. C) epinephrine. D) norepinephrine.

B) MCP.

11) What occurs when an inducer is added to an environment containing an organism with a metabolic pathway controlled by a repressor? A) The inducer combines with the repressor and activates the pathway. B) The inducer combines with the repressor and inactivates the pathway. C) The inducer combines with the substrate and blocks induction. D) The inducer does not combine with, but functions as a chaperone molecule for, the enzyme-substrate complex.

B) The inducer combines with the repressor and inactivates the pathway.

Which of the following is a characteristic of an isoenzyme? A) More than one enzyme is regulated by the same mechanism. B) The same reaction can be catalyzed by multiple enzyme variants. C) Multiple binding sites on the same enzyme enable multiple regulation mechanisms. D) More than one gene makes the same enzyme.

B) The same reaction can be catalyzed by multiple enzyme variants.

Which organism would likely harbor the most two-component regulatory systems? A) an archaeon living in an extreme environment B) a bacterium occupying a heterogeneous niche with high nutrient mixing C) an organism capable of quorum sensing D) a parasitic bacterium living inside another organism

B) a bacterium occupying a heterogeneous niche with high nutrient mixing

A protein region with a specific function and structure is called a A) conserved site. B) domain. C) locale. D) motif.

B) domain.

How is the activity of a riboswitch controlled? A) by other riboswitches B) metabolite binding can change its structure C) sigma factor binding alters its structure D) small RNA complementary binding disrupts its function

B) metabolite binding can change its structure

7) The lac operon is an example of ________ control in which the presence of an ________ is required for transcription to occur. A) negative / activator B) negative / inducer C) positive / activator D) positive / inducer

B) negative / inducer

In order for the helix-turn-helix motif to bind to DNA, the ________ must fit into the major groove of the DNA. A) homeotic switches B) recognition helix C) operator D) zinc fingers

B) recognition helix

Attenuation is a type of regulation that can control A) allosteric enzyme activity. B) transcriptional activity exclusively. C) translational activity exclusively. D) both transcriptional and translational activity.

B) transcriptional activity exclusively.

Most riboswitches control A) transcription. B) translation. C) ribosome synthesis. D) tRNA synthesis.

B) translation.

Which RNA chaperone protein binds the short trans-sRNA sequence to form a complex with its mRNA target? a. TrpC b. Hfq c. SgrS d. RpoS

B. Hfq

Which control mechanism is responsible for Escherichia coli using glucose as a carbon substrate and NOT inducing other pathways? A. catabolite induction B. catabolite repression C. signal transduction D. stringent response

B. catabolite repression

In E. coli, the genes for utilization of maltose are at various locations across the chromosome but are activated by the same maltose activator protein. This is an example of a(n) A. operon. B. regulon. C. riboswitch. D. two-component regulatory system.

B. regulon

To repress transcription, corepressors bind to ________, and inducers bind to ________ proteins. A. repressor proteins / inducer B. repressor proteins / repressor C. RNA polymerase / inducer D. RNA polymerase / repressor

B. repressor proteins / repressor

Phosphorylation of ________ regulates which direction a flagellum rotates, thus controlling whether an organism runs or tumbles. A) CheAW B) CheB C) CheY D) CheZ

C) CheY

An organism grown in nutrient rich broth to high turbidity always produces a blue pigment. When a large inoculum is transferred to a nutrient rich agar plate, it also appears blue. A researcher noticed that this never happens when very small colonies are grown on low nutrient agar plates, however. What is the most plausible conclusion? A) Large populations enabled the differentiation of a subpopulation of cells that created the blue pigment. B) Only high nutrient conditions provide enough energy for cells to produce this secondary metabolite that appears blue. C) Production of the blue pigment production is linked to quorum sensing. D) The strong gradient from very high to low nutrient bioavailability induces production of the blue metabolite.

C) Production of the blue pigment production is linked to quorum sensing.

When the nontemplate strand of a gene is transcribed into RNA, what is likely to result? A) A complementary sRNA will bind to it and form a functional ribozyme with secondary structure. B) It will complementarity bind to the gene sequence, form a hairpin loop, and transcriptionally repress the gene. C) The complementary mRNA transcribed from the template strand will bind to it and halt its translation. D) A global regulator will identify this as a stress, respond by inducing ribonuclease production, and it will be degraded.

C) The complementary mRNA transcribed from the template strand will bind to it and halt its translation.

Quorum sensing is a regulatory system that requires a certain cell density to work effectively. Each of the following activities utilizes quorum sensing EXCEPT A) Staph aureus infection. B) transition of Candida albicans from budding yeast to elongated filaments. C) flagella synthesis in Proteus vulgaris. D) light emission by Aliivibrio fischeri.

C) flagella synthesis in Proteus vulgaris.

During a growth curve of Aliivibrio fischeri, when would you expect to see the strongest bioluminescence? A) lag phase B) early to middle log phase C) late log to early stationary phase D) middle to late stationary phase

C) late log to early stationary phase

The function of a kinase is A) methylation. B) response regulation. C) phosphorylation. D) glycosylation.

C) phosphorylation.

Regulation of enzyme activity occurs A) at the start of transcription. B) at the start of translation. C) posttranslationally. D) at any point on the enzymatic production pathway.

C) posttranslationally

Considering the catabolite repression mechanism, which observation would make you suspect it IS occurring? A) CRP bound to promoter sites B) elevated levels of transcripts for maltose and sucrose catabolism C) relatively low intracellular cyclic AMP levels D) RNA polymerase bound to biosynthetic promoter sequences

C) relatively low intracellular cyclic AMP levels

Which type of regulator(s) specifically binds to operator regions of DNA? A) activators B) activators and inducers C) repressors D) repressors and corepressors

C) repressors

Based on our understanding of the early stages of life, ________ is/are thought to be one of the earliest forms of metabolic regulation that evolved. A) attenuation B) feedback inhibition C) riboswitches D) transcription factors

C) riboswitches

The promoters of positively controlled operons require activator proteins because A) RNA polymerase easily recognizes the consensus sequence. B) they are required to inactivate the repressor proteins. C) the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter. D) they are needed to bind to the allosteric site of RNA polymerase.

C) the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.

For the lac operon in E. coli, under conditions in which glucose is absent and lactose is present, which of the following is true? A. CRP and cAMP together are bound to the DNA, and LacI is bound to the operator site. B. The lac operon is not transcribed because lactose is present. C. CRP and cAMP together are bound to the DNA, and allolactose is bound to LacI. D. The lac operon is not transcribed due to catabolite repression because glucose is absent.

C. CRP and cAMP together are bound to the DNA, and allolactose is bound to LacI.

In Escherichia coli, the cytoplasmic heat shock response is facilitated by σ32 (RpoH), which at high temperatures A. binds to DnaK and degrades proteases. B. binds to unfolded proteins, acting as a chaperone. C. evades protease degradation and functions to induce heat shock gene expression. D. remains unbound and acts as a negative regulator to synthesize DnaK.

C. evades protease degradation and functions to induce heat shock gene expression.

A common motif in proteins that bind DNA in Bacteria is the A. catalytic triad. B. double helix. C. helix-turn-helix. D. turn-helix-turn.

C. helix-turn-helix.

________ occurs when an external signal does NOT directly enter the cell but instead is detected by a sensor that transmits it to the rest of the regulatory machinery. A.Quorum sensing B. Sensory transduction C. Signal transduction D. Two-component regulation

C. signal transduction

The ________ is a bacterial regulatory mechanism used to survive nutrient-poor conditions, antibiotic exposure, and environmental stresses. A. catabolite repression B. heat shock response C. stringent response D. two-component system

C. stringent response

________ pathways typically utilize ________ proteins that stimulate binding of RNA polymerase to DNA. A) Anabolic; repressor B) Catabolic; repressor C) Anabolic; activator D) Catabolic; activator

D) Catabolic; activator

12) Which of the following do NOT bind to the promoter sequence during regulation? A) activators B) inducers C) repressors D) None of these bind directly to the promoter sequence.

D) None of these bind directly to the promoter sequence.

PII proteins are a family of signal-transducing proteins that regulate ________ during nitrogen metabolism. A) transcription factors. B) enzymes. C) membrane transport proteins. D) PII proteins regulate each of the above during nitrogen metabolism.

D) PII proteins regulate each of the above during nitrogen metabolism.

Why are two-component regulatory systems particularly useful for controlling gene expression in response to environmental signals? A) Two proteins controlling a gene means there are two chances to activate a gene. B) Two proteins delay the response time so the cell can be sure the change is permanent. C) One of the two proteins can be exposed to the external environment to receive a signal. D) Phosphorylation is a permanent change so genes are always turned on after signal.

D) Phosphorylation is a permanent change so genes are always turned on after signal.

In negative control of transcription by the lac operon, how does the presence of an inducer affect transcription? A) The inducer binds to the operator. B) The inducer does not bind to the operator. C) The inducer causes the repressor to bind to the operator. D) The inducer prevents the repressor from binding to the operator.

D) The inducer prevents the repressor from binding to the operator.

Chemotaxis in bacteria occurs through the use of A) adaptation. B) quorum sensing. C) autoinduction. D) a modified two-component system.

D) a modified two-component system.

Mechanisms for controlling enzyme activity include all of the following EXCEPT A) degradation of the enzyme. B) feedback inhibition. C) covalent modification of the enzyme. D) addition of short sections of new amino acid sequence.

D) addition of short sections of new amino acid sequence.

A mutation in the gene encoding the lactose repressor (lacI) that prevents lactose from binding to the LacI protein would result in A) constant expression of the lac operon in the absence of lactose. B) constant repression of the lac operon in the absence of lactose. C) constant expression of the lac operon in the presence of lactose. D) constant repression of the lac operon in the presence of lactose.

D) constant repression of the lac operon in the presence of lactose.

A bacterium that either partially or fully catabolizes an acyl-homoserine lactone will likely disrupt A) attenuation. B) chemotaxis. C) endospore formation. D) quorum sensing.

D) quorum sensing.

Regulatory proteins A) are influenced by small molecules. B) bind to specific DNA sites. C) regulate transcription. D) regulate transcription, bind specific DNA sites, and can be influenced by small molecules.

D) regulate transcription, bind specific DNA sites, and can be influenced by small molecules.

All of the following are functions of heat shock proteins in bacteria EXCEPT A) prevention of inappropriate protein subunit aggregation. B) degradation of denatured proteins. C) responding to exposure to high levels of ethanol. D) stimulation of binary fission.

D) stimulation of binary fission.

How would you design an sRNA to bind to a sequence? A) select six continuous nucleotides from the sequence B) take the complementary sequence of six continuous nucleotides C) select 200 continuous nucleotides from the sequence D) take the complementary sequence of 200 continuous nucleotides

D) take the complementary sequence of 200 continuous nucleotides

Which of the following is NOT true of DNA-binding proteins? A. Many are dimers that combine with two sites on the DNA. B. Regulatory proteins often bind inverted repeats on DNA. C. A leucine zipper is a common domain to maintain proper conformation. D. Most bind to DNA in a nonspecific manner.

D. Most bind to DNA in a nonspecific manner.

Pathogenic bacteria such as E. coli O157:H7 and Staphylococcus aureus have a strong selection pressure to refrain from activating an immune response until their numbers are great. ________ is thus an effective way these pathogens control production of certain virulence factors. A. Attenuation B. Differentiation C. Signal transduction D. Quorum sensing

D. Quorum sensing

Induction often occurs for ________ pathways, whereas repression is more common in ________ pathways. A. anabolic / biosynthetic B. anabolic / catabolic C. biosynthetic / anabolic D. catabolic / anabolic

D. catabolic / anabolic

Once a signal from the environment is detected by a sensor kinase, the next step to pass on this signal involves the sensor kinase transferring A. its phosphate to ADP to form ATP. B. its phosphate onto another intracellular signaling molecule. C. phosphate from ATP onto another intracellular signaling molecule. D. phosphate from ATP onto itself.

D. phosphate from ATP onto itself.

In the hyperthermophile Pyrococcus furiosus, TrmBL1 simultaneously represses genes for ________ and activates genes for _________ synthesis. A. nitrogen fixation / glutamine B. glutamine synthesis / nitrogen C. nitrogen assimilation / arginine D. sugar transport / glucose

D. sugar transport / glucose

In catabolic repression, cells always use the least abundant carbon source first.

F

T/F: When environmental levels of amino acids become limited, synthesis of mRNA, rRNA, and tRNA increases immediately. When environmental levels of amino acids become limited, synthesis of mRNA, rRNA, and tRNA increases immediately.

F

True or False: In enzyme induction, an enzyme is made only when its substrate is absent.

False

True or False: sRNAs can only regulate expression by binding mRNA.

False

When arginine is added to a culture already growing exponentially in a medium without arginine, what occurs?

Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

Which of the following do NOT bind to the promoter sequence during regulation? Which of the following do NOT bind to the promoter sequence during regulation? activators inducers repressors None of these bind directly to the promoter sequence.

None of these bind directly to the promoter sequence

An organism grown in nutrient rich broth to high turbidity always produces a blue pigment. When a large inoculum is transferred to a nutrient rich agar plate, it also appears blue. A researcher noticed that this never happens when very small colonies are grown on low nutrient agar plates, however. What is the most plausible conclusion?

Production of the blue pigment production is linked to quorum sensing.

T/F : Proteins required at approximately the same level throughout a cells growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized. Proteins required at approximately the same level throughout a cells growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized.

T

T/F: A common structure for proteins that bind DNA is helix-turn-helix.

T

T/F: A two-component regulatory system usually involves both the sensor and response proteins being subject to phosphorylation

T

T/F: Proteins and RNA molecules that are needed in the cell at about the same level under all growth conditions, require constitutive expression.

T

T/F: Quorum sensing relies upon a large cell population which then turns on transcription. Quorum sensing relies upon a large cell population which then turns on transcription.

T

T/F: Some proteins that bind to DNA block transcription, whereas other proteins activate transcription.

T

T/F: The preferential use of glucose over other available carbon substrates for growth is mechanistically explained by catabolite repression.

T

T/F: The stringent response is a mechanism used by bacteria that provides increased ability to survive in environments lacking nutrients.

T

In negative control of transcription by the lac operon, how does the presence of an inducer affect transcription?

The inducer prevents the repressor from binding to the operator.

True or False: Even when a gene or operon is "fully repressed," some basal level of transcription still occurs.

True

True or False: Often it is the final product of a biosynthetic pathway that acts as a corepressor molecule.

True

Mechanisms for controlling enzyme activity include all of the following EXCEPT

addition of short sections of new amino acid sequence.

The upstream region of an mRNA, acting as a riboswitch, binds a(n) ________ and results in translational blockage of the downstream protein-encoding sequence. a. antisense RNA b. metabolite c. peptide d. RNAi

b. metabolite

Binding of an sRNA to the RBS a. inhibits translation of the mRNA. b. stimulates translation of the mRNA. c. can inhibit or stimulate translation of the mRNA. d. inhibits transcription of the mRNA

c. can inhibit or stimulate translation of the mRNA

Why would cells want to control what protein is expressed?

conserve energy and attain a specific product

needed by the cell all the time, synthesized all the time

constitutive proteins

Attenuation is a transcriptional control mechanism that relies on : a. attenuator molecules binding to mRNA. b. effector proteins to control the binding of RNA polymerase. c. transcriptional feedback inhibition. d. the secondary structure of the mRNA leader.

d. the secondary structure of the mRNA leader.

needed by the cell sometimes, must have induced synthesis

inducible proteins

controlled both positively and negatively

lac operon

Transcriptional regulators bind most frequently at the ________ site of DNA.

major groove

The lac operon is an example of ________ control in which the presence of an ________ is required for transcription to occur.

negative/inducer

The function of a kinase is

phosphorylation

Regulation of enzyme activity occurs

posttranslationally.

In order for the helix-turn-helix motif to bind to DNA, the ________ must fit into the major groove of the DNA.

recognition helix

Regulatory proteins

regulate transcription, bind specific DNA sites, and can be influenced by small molecules.

how do bacteria control what proteins are being expressed?

regulatory systems

When more than one operon is under the control of a single regulatory protein, the operons are collectively called a(n)

regulon

Which type of regulator(s) specifically binds to operator regions of DNA?

repressors

The promoters of positively controlled operons require activator proteins because

the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.