Lac Operon

Lac Operon

a segment of DNA , under the control of the same promoter, found in some prokaryotes allowing for regulation over protein synthesis

Promoter

specific segment of DNA that binds with RNA Polymerase to begin transcription of mRNA from the operon genes

Operator

sequence of nucleotides located between the promoter and structural genes where the repressor protein can bind

Regulator

sequence of DNA found anywhere on the bacterial chromosome; codes for the production of repressor protein. Is not part of the operon.

Inducer

substance which can activate or inactive a repressor (Lactose)

Lac Operon

In the case of the lac operon, lactose is the inducer. If lactose is present, it binds to and inactivates the repressor by causing it to fall off the operator. If lactose operator is free of repressor, then RNA Polymerase is able to bind. If RNA Polymerase can bind to the lac operon, then B-galactosidase is produced, and lactose is catabolized into glucose and galactose for energy. Permease is also produced, which allows more lactose to enter the cell.

The operon is induced when lactose molecules bind to the repressor protein. As a result, the repressor protein loses its shape and falls off of the operator region. Therefore, RNA polymerase can continue transcribing the rest of the operon. After all of the lactose is gone from the environment, then the repressor protein regains its shape and goes back to the operator region. Then, it blocks RNA polymerase from transcribing the genes that produce B-gal and permease.

How is the lac operon induced? How is it "uninduced"?

groups of closely related genes coding for enzymes or other proteins that are all controlled by one promoter

Operon

Transcription

_________ of the operon is controlled by the presence or absence of a regulatory protein bound to the operator

IPTG

_______ is similar in structure to lactose, but it isn't metabolized (broken down and used) by the bacteria, like lactose would be

Xgal

Used to see if the bacteria has been induced to produce Bgal

Xgal

__________ is an indicator that turns blue when lactose is broken down,

Amino Group (NH2)

Carboxylic Acid Group (COOH)

R Group

General Structure of an Amino Acid

Polar R Group

hydrophilic, they'll usually be on the outside where there's water

Non- Polar R Group

hydrophobic, hide in the center away from water

Adding amino acids together to form a peptide bond

The OH From one bonds with the H of another to form H2O

Then, the C and N bond to make a peptide bond

Dehydration Synthesis

Ribosome

Enzyme that catalyzes dehydration synthesis

Primary Protein

Linear chain of protein structure

Secondary Protein

Sheets and helices of protein chain

Tertiary Structure

3-D chain of proteins

Quartiary Structure

Number of parts determine the domains of the proteins...4^0

Polypeptide

Linked amino acids