Deck 6: Microbial Regulatory Systems

Question 1

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

Answer 1

C

Question 2

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.

Answer 2

D

Question 3

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

Answer 3

B

Question 4

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

A) activators
B) activators and inducers
C) repressors
D) repressors and corepressors

Question 5

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.

Question 6

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

A) major groove
B) minor groove
C) histone complex
D) primary supercoil

Question 7

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.

Question 8

________ pathways typically rely on ________ proteins to inhibit mRNA synthesis.

A) Anabolic; repressor
B) Catabolic; repressor
C) Anabolic; activator
D) Catabolic; activator

Question 9

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.

Question 10

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.

Question 11

A protein region with a specific function and structure is called a

A) conserved site.
B) domain.
C) locale.
D) motif.

Question 12

The function of a kinase is

A) methylation.
B) response regulation.
C) phosphorylation.
D) glycosylation.

Question 13

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

Question 14

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.

Question 15

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.

Question 16

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.

Question 17

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

Question 18

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

Question 19

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.

Question 20

Enzyme induction occurs

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

Question 21

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

Question 22

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.

Question 23

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

Question 24

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.

Question 25

Phosphorylation of ________ regulates which direction a flagellum rotates, thus controlling whether an organism runs or tumbles.

A) CheAW
B) CheB
C) CheY
D) CheZ

Question 26

Chemotaxis in bacteria occurs through the use of

A) adaptation.
B) quorum sensing.
C) autoinduction.
D) a modified two-component system.

Question 27

________ pathways typically utilize ________ proteins that stimulate binding of RNA polymerase to DNA.

A) Anabolic; repressor
B) Catabolic; repressor
C) Anabolic; activator
D) Catabolic; activator

Question 28

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.

Question 29

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.

Question 30

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.

Question 31

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

Question 32

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.

Question 33

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

Question 34

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

Question 35

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

Question 36

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

Question 37

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.

Question 38

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 complementarily 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.

Question 39

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.

Question 40

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.

Question 41

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.

Question 42

Most riboswitches control

A) transcription.
B) translation.
C) ribosome synthesis.
D) tRNA synthesis.

Question 43

Global regulatory systems include all of the following EXCEPT

A) amino acid synthesis.
B) transformation.
C) heat shock response.
D) anaerobic respiration.

Question 44

A common structure for proteins that bind DNA is helix-turn-helix.

Question 45

Proteins required at approximately the same level throughout a cellʹs growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized.

Question 46

Cyclic AMP (cAMP) is involved in the global regulation of catabolic pathways in Escherichia coli, including the lac operon. A high activity of the enzyme adenylate cyclase which makes cAMP is suggestive of catabolite repression.

Question 47

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.

Question 48

Some proteins that bind to DNA block transcription, whereas other proteins activate transcription.

Question 49

Depending on the type of regulatory mechanism, activators and repressors can bind to operator regions which control transcription.

Question 50

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

Question 51

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

Question 52

Enzyme repression typically affects catabolic pathways.

Question 53

Short regions at the beginning and end of gene sequences are not translated into proteins.

Question 54

A two-component regulatory system usually involves both the sensor and response proteins being subject to phosphorylation.

Question 55

Small molecules usually act directly (rather than indirectly) in regulating transcription.

Question 56

The residues in a DNA-binding protein that interact with DNA usually correspond to each other according to the amino acids encoded by the DNA. For example, a DNA sequence containing AGC-AGA-CAG which encodes for Ser-Arg-Gln would likely have a DNA-binding protein with the sequence Ser-Arg-Gln.

Question 57

A regulon is composed of at least two operons regulated by the same protein.

Question 58

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.

Question 59

In most cases, the first product of a particular biosynthetic pathway represses the enzymes of the pathway.

Question 60

Once cytoplasmic sensor proteins involved in chemotaxis regulation are phosphorylated, a cascade of other phosphate-transferring mechanisms provides ATP to rotate flagella.

Question 61

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

Question 62

Heat shock proteins are produced in high number to minimize damaging effects during high heat conditions, in addition to other stress signals unrelated to heat such as ultraviolet radiation.

Question 63

Describe the basic two-component regulatory system, and explain the function of each component.

Question 64

The small size of prokaryotic cells limits their ability to respond to spatial gradients of a chemical.

Question 65

Quorum sensing relies upon a large cell population which then turns on transcription.

Question 66

Contrast prokaryotic and eukaryotic regulation of gene expression.

Question 67

Explain why one cell of a pathogenic bacterium by itself typically does not secrete a toxin, despite the species as a whole being characterized as toxin producing. To help in your explanation, predict what would happen to an individual pathogen that secreted a toxin inside a human.

Question 68

Explain the phenomenon known as diauxic growth. Hypothesize why this type of regulation might be important for the survival of a microbe in a mixed population.

Question 69

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

Question 70

Explain the function of cAMP in catabolite repression.

Question 71

During chemotaxis, attractants increase the rate of autophosphorylation, whereas repellants decrease this rate.

Question 72

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

Question 73

Adaptation is based on the level of phosphorylation of MCPs.

Question 74

Using the tryptophan operon as a model, describe the formation of a stem-loop structure and its function.

Question 75

In many environments, the limiting nutrient for bacterial growth is phosphorus.

Question 76

Explain a common mechanism used by cells to ensure proper binding of DNA-binding proteins to DNA.

Question 77

Multiple mechanisms for small RNA (sRNA)-mediated translational regulation exist, but all are unified by inactivating protein synthesis of the target mRNA.

Question 78

How is transcription in Archaea controlled?

Question 79

Explain why is it unsurprising that two-component regulatory systems are all but absent in bacteria that live at the expense of a host.

Question 80

Regulation of transcription in Archaea is more similar to that which occurs in eukaryotes than in bacteria.