chapter 6: regulatory systems

Question 1

multiple outcomes can happen after DNA binding
the binding event can block transcription
what is this called?
*remember transcription is DNA to RNA

Answer 1

NEGATIVE REGULATION

Question 2

multiple outcomes can happen after DNA binding
the binding event can activate trancription
what is this called?

Answer 2

POSITIVE REGULATION

Question 3

a unit made up of linked genes that is thought to regulate other genes responsible for protein synthesis.

Answer 3

OPERONS

Question 4

What are the properties of Operons?

Answer 4

Only found in bacteria
Coordinated set of genes
All regulated as a single unit
Either inducible or repressible

Question 5

encode enzymes that act in catabolism (break down)

induced (turned on) by the presence of the substrate (ex. Lac Operon)

Answer 5

Inducible operons

Question 6

contain genes coding for anabolic enzymes and are repressed by the product synthesized by the enzyme (ex. Trp Operon and A)

Answer 6

Repressible operons

Question 7

what are some features of operons?

Answer 7

regulator
control locus
structural locus

Question 8

gene that codes for a protein capable of repressing the operon (a repressor)

Answer 8

regulator

Question 9

composed of the promoter (recognized by RNA polymerase) and the operator, a sequence that acts as an on/off switch

Answer 9

control locus

Question 10

made up of three genes, each coding for a different enzyme needed to catabolize lactose

Answer 10

structural locus

Question 11

Repressible Operon:

corepressors (argenine) bind to an…?

Answer 11

allosteric repressor protein

Question 12

Allosteric repressor is __and binds to __

Answer 12

activated and binds to operator

Question 13

production of an enzyme in response to presence of substrate

Answer 13

induction

Question 14

what does the inducer do?

Answer 14

binds to repressor and deactivates it (unbinds from dna)

Question 15

what does an inducer typically affect?

Answer 15

catabolic enzymes

ex: lac operon

Question 16

what does an inducer ensure?

Answer 16

that enzymes are synthesized only when needed

Question 17

regulator protein activates the binding of RNA polymerase to DNA

Answer 17

Postive control

Question 18

Maltose catabolism in E. coli:

Maltose activator protein cannot bind to DNA unless it first binds

Answer 18

maltose (inducer)

also known as subsequent binding

Question 19

Activator proteins bind specifically to

Answer 19

activator-binding site

certain dna sequence that is not called an operator

Question 20

regulate expression of many different genes simultaneously (e.g., lactose operon and maltose regulon)

Answer 20

Global control systems

Question 21

what is an example of global control.

Answer 21

Catabolite repression

Question 22

what does catabolite repression do?

Answer 22

controls use of carbon sources if more than one present
Synthesis of unrelated catabolic enzymes (e.g., lactose operon and maltose regulon) is repressed if glucose is present in growth medium.
also called “glucose effect”
ensures that the “best” carbon and energy source is used first

Question 23

two exponential growth phases if two energy sources available

Answer 23

Diauxic growth

Question 24

how does Diauxic growth work?

Answer 24

better energy source consumed first, growth stops

After lag, growth resumes with second energy source.

Question 25

T/F Prokaryotes can respond to the presence of other cells of the same species.

Answer 25

True

Question 26

mechanism by which Bacteria and some Archaea assess their population density.

Answer 26

Quorum sensing

Question 27

what is the significance of quorum sensing

Answer 27

ensures that a sufficient number of cells are present before initiating a response that, in order to be effective, requires a certain cell density Ex: toxin production

Question 28

Each species of bacterium produces a specific autoinducer signaling molecule what are some of the properties of auto inducers?

Answer 28

* diffuses freely across the cell envelope * will reach high concentrations in the cell only if many cells are nearby and making the SAME autoinducer * binds to specific activator protein or sensor kinase, triggering transcription of specific genes

Question 29

what was the first autoinducer to identified?

Answer 29

AHL

Question 30

This autoinducer is common among gram negative species

Answer 30

AI-2

Question 31

This type of autoinducer is used by gram postive

Answer 31

short peptides

Question 32

Quorum sensing was first discovered as a mechanism for?

Answer 32

regulating light production in bacteria including Aliivibrio fischeri

Question 33

Lux operon encodes

Answer 33

bioluminescence

Question 34

shiga-toxin strain produces...?

Answer 34

AHL AI-3 that induces virulence genes

Question 35

Epinephrine plus norepinephrine plus AI-3 bind to | and what does it activate

Answer 35

sensor molecules in plasma membrane activates motility, toxin secretion, and production of lesion-forming proteins

Question 36

Virulence factors example: Staphylococcus aureus how do they secrete viruses?

Answer 36

secretes small peptides that damage host cells or alter host's immune system under control of autoinducing peptide (AIP) activates several proteins that lead to production of virulence proteins

Question 37

how can Quorum-sensing disruptors help?

Answer 37

potential drugs for dispersing biofilms and preventing virulence gene expression.

Question 38

40–400 nucleotides that regulate gene expression in prokaryotes and eukaryotes

Answer 38

small RNAs (sRNAs)

Question 39

what do regulatory RNA's do ?

Answer 39

block a ribosome-binding site (RBS), decreasing expression open up a blocked RBS, increasing expression increase degradation of mRNA, preventing synthesis decrease degradation of mRNA, increasing synthesis

Question 40

RNA molecules that resemble repressors and activators in binding small metabolites and regulating gene expression

Answer 40

Riboswitches:

Question 41

Mechanisms of riboswitches

Answer 41

Metabolite binds directly to mRNA. control translation of mRNA instead of transcription small molecule binding domain at 5′ end of mRNA two alternative structures, one with small molecule bound and other without

Question 42

mechanism for temporarily turning off the reactions in a biosynthetic pathway

Answer 42

Feedback inhibition

Question 43

how does feedback inhibition work ?

Answer 43

the end product will send a feed back mechanism that will shut down the allosteric enzyme this changes the conformation preventing substrate binding