Biology 2581B Study Guide - Plasmid, Lactose Permease, Lac Operon

• School: Western University
• Department: Biology
• Course: Biology 2581B
• Professor: Jim Karagiannis

Document Summary

Monday march 4th, 2013: coli biphasic growth curve: At time 0, both glucose and lactose are added to the e. coli media. During phase i, the e. coli experience growth until glucose is depleted and during phase ii, the e. coli experience growth until lactose is depleted. The simple monosaccharide glucose is preferred over the disaccharide lactose as a better carbon and energy source since it can be used immediately and doesn"t need to be broken down. Interestingly, -galacotosidase (the enzyme responsible for lactose metabolism) is produced in phase ii, but not in phase i. Two genes are critical for the breakdown of lactose into simpler sugars: the lacy gene (which encodes lactose permease) and the lacz gene (which encodes -galacotosidase). Lactose permease is the membrane protein that is involved in transporting lactose into the cell, while - galacotosidase is the enzyme responsible for breaking lactose down.