Question 1

In some circumstances,when two different carbon sources are available,growth will occur first using one carbon source,then after a short lag period,growth will resume using the second carbon source.This process is called __________ growth.

Accepted Answer

This process is called diauxic growth, where bacteria preferentially use the first carbon source until it is depleted, then undergo a lag phase before switching to the second carbon source for continued growth.

Question 2

What is the key factor determining whether or not attenuation will occur when transcription of the

Accepted Answer

The key factor determining whether or not attenuation will occur during the transcription of the E. coli trp operon is the level of trp-tRNA that is charged with tryptophan. When levels of charged trp-tRNA are high, indicating an abundance of tryptophan, the ribosome quickly translates the leader peptide, allowing the formation of a terminator structure in the mRNA that halts transcription (attenuation). Conversely, when charged trp-tRNA levels are low, indicating tryptophan scarcity, the ribosome stalls, and a different mRNA structure forms that allows transcription to continue.

Question 3

When a repressor binds to the operator site on the DNA it normally

Accepted Answer

Repressors bind to the operator site on DNA to inhibit the initiation of transcription, preventing RNA polymerase from transcribing the genes downstream of the operator.

Question 4

Enzymes that are expressed at a constant level all the time are said to be:

Accepted Answer

Enzymes that are expressed at a constant level all the time are said to be constitutive. This means that their expression is not regulated and they are needed continuously by the cell for its normal metabolic processes. Inducible enzymes are those whose expression is induced in response to specific environmental signals, while repressible enzymes are those whose expression is repressed in response to specific environmental signals. Attenuated enzymes do not have a clear definition in this context.

Question 5

Which of the following is not a regulatory mechanism used to control the tryptophan operon in Escherichia coli?

Accepted Answer

Catabolite repression is not a regulatory mechanism used to control the tryptophan operon in Escherichia coli. Repression, attenuation, and feedback inhibition are all regulatory mechanisms used to control the tryptophan operon in E. coli.

Question 6

Which of the following is not a regulatory mechanism used to control the lactose operon in Escherichia coli?

Accepted Answer

Attenuation is a regulatory mechanism used in some operons, like the tryptophan operon, but not in the lactose operon. The lactose operon is primarily regulated by induction and catabolite repression.

Question 7

What term describes a set of genes that is controlled by a common regulatory protein?

Accepted Answer

A regulon is a set of genes that is controlled by a common regulatory protein.

Question 8

An operon network that is under the control of a common regulatory protein while each operon is still also under the control of its own unique regulatory protein is most specifically referred to as a

Accepted Answer

The answer of An operon network that is under the...

Question 9

The terminator versus anti-terminator function of the T box-based riboswitch used by Gram-positive bacteria to regulate amino acid-related genes is determined by

Accepted Answer

The terminator versus anti-terminator function of the T box-based riboswitch is determined by the binding of the appropriate uncharged tRNA. When the amino acid levels are low, the corresponding tRNA is uncharged and can bind to the T box region of the mRNA, leading to the formation of an anti-terminator secondary structure that allows transcription to continue. When the amino acid levels are high, the corresponding tRNA is charged and cannot bind to the T box region, leading to the formation of a terminator secondary structure that prematurely ends transcription.

Question 10

The site on the DNA to which a repressor protein binds is the __________.

Accepted Answer

The site on the DNA to which a repressor protein binds is called the operator. The operator is located within an operon, which is a cluster of genes that are regulated together. The promoter is the site on the DNA where RNA polymerase binds to initiate transcription. The regulator is a protein or other molecule that controls gene expression by binding to DNA.

Question 11

Riboswitches that can block the initiation of translation because of a conformational change that occurs in the leader sequence of an mRNA when the appropriate regulatory effector binds the mRNA achieve that blockage of translation initiation by the occlusion of

Accepted Answer

Riboswitches can block translation initiation by causing a conformational change that hides the Shine-Dalgarno sequence, preventing ribosome binding and thus translation initiation.

Question 12

If Escherichia coli is cultured in broth containing both glucose and lactose,it

Accepted Answer

E. coli prefers to use glucose as a source of energy and will use it first if both glucose and lactose are present. Once the glucose is exhausted, it will use lactose as a secondary source of energy. This process is known as catabolite repression.

Question 13

The __________ is a factor-independent termination site found in the leader region of certain operons,which,under the influence of ribosome behavior,controls the continued transcription of that operon.

Accepted Answer

The description matches that of an attenuator, which is a regulatory sequence found in the leader region of certain operons that controls transcription termination based on ribosome behavior. The other choices (modulator, operator, and terminator) do not fit the specific criteria described.

Question 14

__________ activate repressor proteins thereby decreasing the synthesis of certain enzymes.

Accepted Answer

Corepressors activate repressor proteins, which decrease the synthesis of certain enzymes. Inducers, on the other hand, bind to activator proteins and increase the synthesis of certain enzymes. Effectors are molecules that can directly or indirectly regulate the activity of enzymes or other proteins. Modulators are substances that regulate the activity of enzymes or other proteins by binding to them and altering their activity or their affinity for other molecules.

Question 15

The activity of adenyl cyclase is influenced by

Accepted Answer

The activity of adenyl cyclase is influenced by the phosphotransferase system, which is a regulatory system that controls the transport and metabolism of sugars in bacterial cells. The presence of lactose in the environment and homoserine lactones are not known to directly affect the activity of adenyl cyclase.

Question 16

______________ is used to control transcription of some anabolic pathways involved in amino acid biosynthesis.

Accepted Answer

Attenuation is a regulatory mechanism that controls transcription of some anabolic pathways involved in amino acid biosynthesis. This mechanism allows cells to sense the levels of amino acids and make adjustments in the expression of genes involved in biosynthesis accordingly.

Question 17

Most

Accepted Answer

E. coli antisense RNAs work with a protein called Hfq to regulate their target mRNAs. CAP and MicF are not involved in this process.

Question 18

__________ alter repressor proteins thereby increasing the rate of transcription initiation.

Accepted Answer

Inducers are small molecules that bind to repressor proteins and cause a conformational change that prevents them from binding to DNA. This allows RNA polymerase to bind to the promoter region and initiate transcription, ultimately increasing the rate of transcription initiation.

Question 19

Posttranslational regulation occurs after a protein has been synthesized,and can occur by

Accepted Answer

Allosteric regulation and covalent modification are both mechanisms that can regulate a protein's function after it has been synthesized, thus occurring posttranslationally.

Question 20

When bound to the DNA,the repressor protein usually prevents attachment of the RNA polymerase to the __________.

Accepted Answer

The RNA polymerase binds to the promoter region of the operon in order to initiate transcription. The operator region is located near the promoter and is where the repressor protein binds when it is active. When the repressor protein is bound to the operator, it blocks the RNA polymerase from binding to the promoter and initiating transcription. Therefore, the correct answer is C, promoter.

Quiz 14: Regulation of Bacterial Cellular Processes