Final answer:
The correct substrate for β-galactosidase is C) Lactose. Lactose is a disaccharide consisting of galactose and glucose linked by a β-1,4-glycosidic bond. β-galactosidase hydrolyzes this bond to produce glucose and galactose.
Step-by-step explanation:
The substrate for β-galactosidase is C) Lactose. Lactose is a disaccharide that is composed of two monosaccharide units, galactose, and glucose. These two units are joined by a β-1,4-glycosidic linkage to form lactose, which is commonly referred to as milk sugar. When β-galactosidase acts on lactose, it hydrolyzes the β-1,4-glycosidic bond, thereby producing glucose and galactose.
A bit more about the monosaccharides involved: both glucose and galactose are classified as aldoses, which means they are sugars with an aldehyde group. On the other hand, fructose is a ketose, meaning it has a ketone group. Although glucose, galactose, and fructose are isomers with the same chemical formula (C6H12O6), their structures are different.
The digestion of lactose in certain bacteria like E. coli begins with its hydrolysis by β-galactosidase, an enzyme encoded by the lacZ gene, which is part of a coordinately regulated operon involved in lactose utilization.