Question

In the presence of glucose and lactose, Escherichia coli utilizes glucose. However, lactose also enters the cells because

(A) low level of permease is always present in the cell

(B) it uses the same transporter as glucose

(C) if diffuses through the bacterial cell membrane

(D) it is transported through porins

Answer 1

Correct option (A) low level of permease is always present in the cell

Explanation:

The preferred molecule is glucose first, then lactose is used by E.coli because ultimately lactose is also broken down into galactose and glucose. Permease is a carrier protein which helps in facilitated diffusion. Lac operon is always operational at low levels.