Bio Lecture 23

Front 1

how does individual bacteria respond to environmental change?

Back 1

By regulating their gene expression.

**They respond to environmental fluntuations by metabolic control

Front 2

metabolic control occurs on two levels what are they?

Back 2

1. cells can adjust the activity of enzymes already present. A fast response, which relies on the sensitivity of many enzymes to chemical cues that incr or decr thier catalytic activity

2. Cell can adjust the amt of substance being made of certain enzymes. That is they can regulate the expression of the genes encodig the enzymes.

Front 3

The control of enzymes production occurs at the level of ______.

Back 3

trancription

Front 4

The basic machanism for this control of gene expression in bacteria is descride as _____

Back 4

operon model

Front 5

what is the advantage of grouping genes of related funtions into one trancription unit?

Back 5

is that a single on-off "switch" can control the whole cluster of functionally related genes

Front 6

the switch is a segment of DNA called an _____

Back 6

operator
**position w/in the promoter or b/w the promoter and the enzyme encoding the genes.

Front 7

what does the operator control?

Back 7

it controls the acess of RNA polymerase to the genes

**all togehter, the operator, the promoter, and the genes-- they control the entire stretch of DNA required for enzyme reduction

Front 8

[if the operator is the switch for controlling transcription how does this switch work?]

Back 8

by it self, the (___) operon is turned on, that is RNA polymerase can bind to the promoter and transcribe the genes of the operon. The operon can be switched off by a protein (___) repressor. The repressor binds to the operator and blocks attachment of RNA polymerase to the promoter (preventing transcription of genes)

Front 9

A repressor is a product of _____

Back 9

regulatory gene, which is located some distance away from the operon it controls and has its own promoter

Front 10

The operon is said to be a ____

Back 10

repressible operon b/c transcription is usally on but can be inhibited (repressed)

Front 11

inducible operon is

Back 11

usually off but can be stimulated (induced) when a molecule interacts w/ a regulatory protein

Front 12

what is an example of inducible operon

Back 12

lac operon

Front 13

lactose metabolism begins w/ hydrolysis of the disaccharide into its component _____

Back 13

monosaccharides, glucose and galactose, a reaction catalyzed by the enzyme Beta galactosidase

Front 14

Beta galactosidase is part of the ____

Back 14

lac operon

Front 15

E coli uses three enzmyes to take up and metabolize lactose. the genes for these three enzymes are clustered in the lac operon. these three genes are

Back 15

lacZ--- codes for B-galactosidase, which hydroyzes lactose to glucose and galactose.

lacY-- codes for a permease, the membrane protein that transports lactose into the cell

lacA-- codes for an enzyme caled transacetylase, whose function in lactose metabolism is still unclear

Front 16

The gene, LacI, located outside the operon, codes for an ______ protein that can switch off the lac operon by binding to the operator

Back 16

allosteric repressor


**the lac repressor (protein) is active all by itself, binding to the operator and switching the lac operon off.

Front 17

what inactivates the repressors?

Back 17

a specific small molecule called an inducer (allolactose)

Front 18

In the absence of lactose the lac repressor is in [active/inactive configuration]

Back 18

active configuration

Front 19

if lactose is added to the cell's surrounding, allolactose binds to the _____ and alters its conformation

Back 19

lac repressorin

Front 20

in gene regulation the enzymes of the lactose pathway are referred to as ____

Back 20

inducible enzymes--- functions in catabolic pathway conserving energy

Front 21

regulation of lac operons involves the negative control of genes, because the operons are

Back 21

swtiched off by active form of the repressor protein

Front 22

gene regulation is said to be positive only when a regulatory proteins

Back 22

interacts directly with the genome to switch transcription on

Front 23

[positve gene regulation]
[How does the E.coli sense the glucose concentration and how is this information relayed to the genome?] what is the mechanism for this

Back 23

the mechanism depends on the interaction of an allosteric regulatory protein with a small organic molecule cyclic AMP (which accumulates when glucose is scarce)

Front 24

the regulatory protein called _____, is an activator of transcription.

Back 24

catabolite activator protein (CAP)

Front 25

when cAMP binds to CAP, the regulatory protein (CAP) assumes its active shape and can bind to a specific site at the upstream end of the lac promoter ---- what does this do to the promoter?

Back 25

it stimulates gene expression

Front 26

if the amto of glucose in the cell increases, the cAMP conctrations rise/fall

Back 26

falls

Front 27

trascription of the lac operon proceeds at only a ____

Back 27

low level