A flippase is an enzyme that moves lipids from one side of a lipid bilayer to another in order to maintain the concentrations of specific lipids on each side of the bilayer.Which of the following can be said regarding the reaction of the flippase enzyme?

A)it works against a concentration gradient and requires ATP
B)it works against a concentration gradient but does not require ATP
C)it works with a concentration gradient and requires ATP
D)it works with a concentration gradient but does not require ATP
E)none of the above