Bacterial Replication and Transcription 5.4

Question 1

Attenuation

Answer 1

is a mechanism whereby gene expression (typically at the level of transcription) is controlled after initiation of RNA synthesis

Question 2

Attenuation mechanisms involve a coupling of?

Answer 2

transcription and translation regulation

Question 3

Attenuation can only occur in?

Answer 3

prokaryotes where transcription and translation occur simultaneously

Question 4

Attenuation is utilized in operons for?

Answer 4

amino acid biosynthetic enzymes

Question 5

transcription of mRNA for biosynthetic enzymes does not begin until?

Answer 5

the level of the amino acid is low

Question 6

A leader peptide is enriched in?

Answer 6

amino acids of that biosynthetic pathway

Question 7

Leader peptide is derived from the first

part of the?

Answer 7

polycistronic message

Question 8

attenuation ribosomes translate the

leader mRNA to yield?

Answer 8

amino acid rich leader peptide

Question 9

Amino acid excess affects on leader peptide?

Answer 9

 In excess situation the mRNA for leader is fully translated
 Thus the mRNA exhibits conformation (stem loop hairpin) that inhibits further transcriptionthis is the inhibitory stem loop terminating transcription.

Question 10

Amino acid starvation affects on leader peptide?

Answer 10

 amino acid starved cell will have partially translated leader that lacks this amino acid -stall
 partially translated mRNA exhibits different conformation with a different stem loop that does not inhibit further transcription

Question 11

another name for post-translational

control?

Answer 11

feedback inhibition

Question 12

What is feedback inhibition?

Answer 12

An important type of regulation of enzyme activity is feedback inhibition (post-translational control), in which the final product of a biosynthetic pathway inhibits the first enzyme unique to that pathway

Question 13

Feedback inhibition is most effective to control catabolic or anabolicpathways

Answer 13

anabolic

Question 14

Allosterism depends on?

Answer 14

non-covalent interaction between an allosteric effector and an allosteric enzyme

Question 15

allosteric enzyme has what two binding sites?

Answer 15

1) acitve site

2) allosteric site

Question 16

active site vs allosteric site

Answer 16

active= where the substrate binds
allosteric= where the inhibiotr binds

Question 17

Binding of the allosteric effector changes

the?

Answer 17

conformation of the active site

*typically makes it so a substrate can no longerbind to the active site