C6 Brock Sample Questions

Question 1

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

Answer 1

D) at any point on the enzymatic production pathway.

Enzyme activity can be regulated at various stages, including transcription, translation, post-translation, and feedback inhibition. This flexibility allows for efficient control of metabolic pathways.

Question 2

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.

Answer 2

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

Arginine’s presence typically inhibits the production of enzymes involved in its synthesis through feedback inhibition, a common regulatory mechanism. Growth continues as the cells can utilize the provided arginine.

Question 3

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.

Answer 3

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

Regulatory proteins (e.g., transcription factors) bind to specific DNA sequences to control gene expression. Their activity can be modulated by small molecules, such as metabolites or hormones.

Question 4

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

Answer 4

B) domain.

Domains are conserved, self-folding parts of proteins with distinct functions. They can be found in various proteins, facilitating modular protein evolution.

Question 5

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

Answer 5

A) major groove

The major groove of DNA provides a more accessible and spacious region for protein-DNA interactions, allowing regulators to recognize and bind specific sequences.

Question 6

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

Answer 6

C) repressors

Repressor proteins bind to operator sequences, blocking RNA polymerase’s access to the promoter and thereby inhibiting transcription of the associated operon.

Question 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

Answer 7

D) positive / inducer

The lac operon is a classic example of positive control, where the presence of an inducer (allolactose or a similar molecule) is necessary to activate transcription by preventing the repressor from binding.

Question 8

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

Answer 8

A) when the substrate is present.

Enzyme induction is a process where the presence of a substrate (or an analog) leads to increased production of the enzyme responsible for its metabolism.

Question 9

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

Answer 9

C) relatively low intracellular cyclic AMP levels

Catabolite repression involves the reduction of cyclic AMP (cAMP) levels in response to preferred carbon sources, leading to decreased transcription of non-essential genes.

Question 10

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 10

C) late log to early stationary phase

Bioluminescence in Aliivibrio fischeri is often regulated by quorum sensing, which is typically activated at higher cell densities, such as those found in late log to early stationary phase.

Question 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.

Answer 11

D) The inducer does not combine with, but functions as a chaperone molecule for, the enzyme-substrate complex.

Note: This answer might be slightly misleading; a more accurate description would involve the inducer binding to the repressor, preventing it from binding to the operator. The inducer typically binds to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator, thus allowing transcription to proceed.

Question 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.

Answer 12

B) inducers

Inducers typically bind to repressor proteins, not directly to promoter sequences. This binding causes a conformational change in the repressor, affecting its ability to bind the operator.

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

Answer 13

A) adenylate cyclase / catabolite repression

Adenylate cyclase is the enzyme responsible for converting ATP into cyclic AMP (cAMP), a key molecule in catabolite repression and other signaling pathways.

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.

Answer 14

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

The inducer binds to the lac repressor, causing a conformational change that prevents the repressor from binding to the operator, thus allowing RNA polymerase to initiate transcription.

Question 15

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 15

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

Common mechanisms for controlling enzyme activity include degradation, feedback inhibition, and covalent modification. Adding new amino acid sequences is not a typical regulatory mechanism.

Question 16

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

Answer 16

C) phosphorylation.

Kinases are enzymes that transfer phosphate groups from high-energy donor molecules to specific substrates, a process known as phosphorylation.

Question 17

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.

Answer 17

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

In positive control, activator proteins are necessary to enhance the binding of RNA polymerase to the promoter, facilitating the initiation of transcription.

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

Answer 18

B) eukaryotes; regulatory proteins

Archaeal transcriptional control mechanisms show more similarity to those of eukaryotes, often involving regulatory proteins to control gene expression.

Question 19

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.

Answer 19

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

Small regulatory RNAs (e.g., siRNAs, miRNAs) primarily function by base pairing with target RNAs, leading to degradation, translational repression, or other regulatory outcomes.

Question 20

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

Answer 20

A) Anabolic; repressor

Anabolic pathways, which synthesize complex molecules from simpler ones, often use repressor proteins to inhibit mRNA synthesis when the end product is abundant, preventing unnecessary production.

Question 21

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

Answer 21

C) Anabolic; activator

Anabolic pathways frequently employ activator proteins to enhance the recruitment of RNA polymerase to the promoter, thereby stimulating the transcription of genes necessary for the pathway.

Question 22

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

Answer 22

A) histidine

In bacterial two-component systems, sensor kinases typically phosphorylate histidine residues on the sensor protein, which then phosphorylates an aspartate residue on the response regulator.

Question 23

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
B) transition of Candida albicans from budding yeast to elongated filaments.
C) flagella synthesis in Proteus vulgaris.
D) light emission by Aliivibrio fischeri.

Answer 23

A) Staph aureus

Quorum sensing relies on the accumulation of signaling molecules to a threshold concentration, indicative of a certain cell density, to regulate various group behaviors.

Question 24

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

Answer 24

D) a modified two-component system.

Bacterial chemotaxis involves a signaling pathway that is essentially a modified two-component system, where sensor proteins (e.g., methyl-accepting chemotaxis proteins) interact with response regulators (e.g., CheY) to control flagellar rotation.

Question 25

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.

Answer 25

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.

It’s plausible for one regulator to bind the operator (e.g., a repressor) and another to bind the promoter (e.g., an activator), allowing for complex, combinatorial control of the operon.

Question 26

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

Answer 26

D) take the complementary sequence of 200 continuous nucleotides

Designing an sRNA to bind a target sequence typically involves creating a complementary sequence to the target. The length can vary, but 200 nucleotides would provide a strong, specific interaction.

Question 27

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.

Answer 27

B) It will complementarily bind to the gene sequence, form a hairpin loop, and transcriptionally repress the gene.

Transcribing the nontemplate strand can produce an antisense RNA, which can bind to the mRNA, forming a hairpin loop, and potentially repressing gene expression through mechanisms like RNA interference.

Question 28

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

Answer 28

C) riboswitches

Riboswitches, being RNA elements that directly sense metabolites, are considered ancient regulatory mechanisms, likely evolving early in life’s history due to their simplicity and effectiveness.

Question 29

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.

Answer 29

B) transcriptional activity exclusively.

Attenuation is a mechanism that regulates transcription by controlling the premature termination of mRNA synthesis in response to the availability of amino acids or other metabolic signals.

Question 30

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.

Answer 30

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

Isoenzymes (or isozymes) are different molecular forms of an enzyme that catalyze the same chemical reaction but may differ in their regulatory properties, substrate affinities, or tissue distribution.

Question 31

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

Answer 31

D) negative control

Negative control typically involves the binding of a regulatory protein (repressor) to DNA to block transcription, which doesn’t inherently require a conformational change in the enzyme itself to alter its activity.

Question 32

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.

Answer 32

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

The observation suggests that the production of the blue pigment is dependent on cell density (high in broth and large inoculum on agar, but not in small colonies on low nutrient agar), which is a hallmark of quorum sensing regulation.

Question 33

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.

Answer 33

D) quorum sensing.

Acyl-homoserine lactones (AHLs) are signaling molecules used in quorum sensing by many Gram-negative bacteria. Catabolizing AHLs would disrupt this signaling pathway.

Question 34

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

Answer 34

C) CheY

In the chemotaxis pathway of bacteria, the phosphorylation state of CheY determines whether the flagella rotate clockwise (tumbling) or counterclockwise (running), influencing the cell’s movement.

Question 35

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

Answer 35

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

Two-component systems are pivotal for responding to environmental changes. An organism living in a heterogeneous, dynamic environment would benefit from having multiple such systems to adapt to the varying conditions.

Question 36

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

Answer 36

B) metabolite binding can change its structure

Riboswitches are RNA elements whose structure changes upon binding to specific metabolites. This conformational change can then regulate gene expression by influencing transcription or translation.

Question 37

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.

Answer 37

A) constant expression of the lac operon in the absence of lactose.

If the LacI repressor cannot bind lactose (or allolactose), it will continuously repress the lac operon, even when lactose is present. However, if the mutation prevents the repressor from binding to the operator, the outcome would be constant expression, as stated.

Question 38

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.

Answer 38

C) One of the two proteins can be exposed to the external environment to receive a signal.

Two-component systems consist of a sensor kinase that can be exposed to the environment (often through the cell membrane) and a response regulator. This architecture allows for the direct sensing of external signals.

Question 39

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

Answer 39

B) recognition helix

The helix-turn-helix (HTH) motif is a common feature of DNA-binding proteins. The “recognition helix” of the HTH motif specifically interacts with the major groove of the DNA, where it can read the base pair sequence.

Question 40

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.

Answer 40

B) MCP (Methyl-Accepting Chemotaxis Protein)

While MCP is crucial for bacterial chemotaxis, the specific interaction between E. coli O157:H7 and its host during infection primarily involves other signaling molecules like AI-3, epinephrine, and norepinephrine, which the pathogen can sense to regulate its virulence.

Question 41

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

Answer 41

B) transformation.

Transformation refers to the direct uptake and incorporation of exogenous genetic material from its surroundings, which is distinct from global regulatory systems that coordinate gene expression in response to environmental or cellular states.

Question 42

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.

Answer 42

A) regulon

A regulon is a set of operons or genes that are regulated by a single regulatory protein (or a small set of closely related proteins), ensuring coordinated expression in response to a particular signal.

Question 43

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

Answer 43

B) translation

While some riboswitches can regulate transcription, the majority of characterized riboswitches control gene expression at the level of translation, often by influencing the ribosome’s access to the mRNA.

Question 44

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.

Answer 44

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

PII proteins are indeed involved in the regulation of various aspects of nitrogen metabolism, including the control of transcription factors, enzymes, and membrane transport proteins, to optimize nitrogen acquisition and utilization.

Question 45

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.

Answer 45

D) stimulation of binary fission

Heat shock proteins (HSPs) in bacteria are primarily involved in protecting proteins from denaturation, facilitating their proper folding, and degrading irreparably damaged proteins. They do not directly stimulate binary fission, which is the process of cell division.

Question 46

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

Answer 46

TRUE

Housekeeping proteins, essential for basic cellular functions, are often constitutively expressed, meaning their synthesis is not heavily regulated and occurs at a relatively constant level.

Question 47

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

Answer 47

TRUE

These regions, known as untranslated regions (UTRs), flank the coding sequence of a gene and are not translated into protein.

Question 48

T/F: Small molecules usually act directly (rather than indirectly) in regulating transcription.

Answer 48

FALSE

Small molecules often act indirectly by binding to regulatory proteins (e.g., transcription factors), which then influence transcription.

Question 49

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

Answer 49

TRUE

The helix-turn-helix motif is a well-known structure in proteins that bind DNA, facilitating specific interactions with the major groove.

Question 50

T/F: 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.

Answer 50

FALSE

The specificity of protein-DNA interactions does not directly correlate with the amino acid sequence encoded by the DNA being bound; rather, it’s determined by the 3D structure and chemical properties of the protein’s DNA-binding domain.

Question 51

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

Answer 51

TRUE

This statement accurately describes the functions of repressor and activator proteins in regulating gene expression.

Question 52

T/F: Enzyme repression typically affects catabolic pathways.

Answer 52

TRUE

Enzyme repression is a common regulatory mechanism in catabolic pathways to prevent unnecessary metabolism of substrates when they are abundant.

Question 53

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

Answer 53

TRUE

Both activators and repressors can indeed bind to operator regions, depending on the regulatory mechanism, to either enhance or inhibit transcription.

Question 54

T/F: A regulon is composed of at least two operons regulated by the same protein.

Answer 54

TRUE

A regulon by definition consists of multiple operons (or genes) that are coordinately regulated by a single regulatory protein.

Question 55

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

Answer 55

TRUE

Catabolite repression is the mechanism by which cells preferentially utilize glucose over other carbon sources by repressing the genes involved in the metabolism of those other sources.

Question 56

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

Answer 56

TRUE

Constitutive expression ensures that essential proteins and RNAs are always available at a relatively constant level, regardless of growth conditions.

Question 57

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

Answer 57

TRUE

In two-component systems, the sensor kinase phosphorylates the response regulator, which is a key mechanism for signal transduction.

Question 58

T/F: 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.

Answer 58

TRUE

cAMP plays a crucial role in regulating catabolic pathways, including the lac operon, by influencing the activity of the CRP (cAMP receptor protein) transcription factor.

Question 59

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

Answer 59

FALSE

The phosphorylation cascade in chemotaxis regulates the direction of flagellar rotation (tumbling vs. smooth swimming) but does not directly provide ATP for rotation; ATP is generated through cellular metabolism.

Question 60

T/F: In most cases, the first product of a particular biosynthetic pathway represses the enzymes of the pathway.

Answer 60

TRUE

Feedback inhibition, where the end product of a biosynthetic pathway inhibits an earlier step, is a common regulatory mechanism to prevent overproduction.

Question 61

T/F: In catabolic repression, cells always use the least abundant carbon source first.

Answer 61

FALSE

Catabolic repression actually leads to the preferential use of the most favorable (often most abundant) carbon source, with the metabolism of less favorable sources being repressed.

Question 62

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

Answer 62

FALSE

Prokaryotic cells, despite their small size, can respond to spatial gradients through chemotaxis, allowing them to move towards or away from chemicals.

Question 63

T/F: Adaptation is based on the level of phosphorylation of MCPs

Answer 63

TRUE

In chemotaxis, the level of phosphorylation of Methyl-Accepting Chemotaxis Proteins (MCPs) plays a crucial role in the adaptation process, allowing cells to reset their sensitivity to stimuli.

Question 64

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

Answer 64

TRUE

Quorum sensing is a regulatory mechanism that relies on the accumulation of signaling molecules to a threshold, indicative of a large cell population, to activate or repress transcription of specific genes.

Question 65

T/F: During chemotaxis, attractants increase the rate of autophosphorylation, whereas repellants decrease this rate.

Answer 65

TRUE

The binding of attractants to chemoreceptors increases the rate of autophosphorylation of the associated kinase, while repellants have the opposite effect, influencing the direction of flagellar rotation.

Question 66

T/F: 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.

Answer 66

TRUE

Heat shock proteins (HSPs) are indeed produced in response to high temperatures and other forms of cellular stress, including UV radiation, to protect proteins from denaturation.

Question 67

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

Answer 67

TRUE

The transcriptional regulation mechanisms in Archaea share more similarities with those of eukaryotes, such as the use of TATA-binding proteins, than with the mechanisms found in bacteria.

Question 68

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

Answer 68

TRUE

The stringent response, triggered by nutrient starvation, involves the production of (p)ppGpp, which in turn regulates transcription and translation to promote survival under nutrient-poor conditions.

Question 69

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

Answer 69

FALSE

Under amino acid limitation, cells often reduce the synthesis of non-essential RNAs and proteins to conserve resources, rather than increasing their production.

Question 70

T/F: In many environments, the limiting nutrient for bacterial growth is phosphorus.

Answer 70

TRUE

Phosphorus is a critical nutrient for bacterial growth, and in many environments, its availability can be limiting, affecting bacterial populations and community structures.

Question 71

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

Answer 71

FALSE

While many sRNA-mediated translational regulation mechanisms indeed inactivate protein synthesis of the target mRNA (e.g., by occluding the ribosome binding site (RBS)), this is not universally true for all mechanisms.