Q. 13.46 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify the disaccharide that fits each of the following descriptions:

a. not a reducing sugar

b. composed of two glucose units

c. also called milk sugar

d. hydrolysis gives glucose and fructose

Step-by-Step Solution

Answer

Part a. Sucrose is not a reducing sugar

Part b. Maltose is composed of two glucose units

Part c. Lactose is also called as milk sugar

Part d. Hydrolysis of sucrose gives glucose and fructose

Step 1: Introduction about reducing sugar (Part a)

• A reducing sugar is one that reduces another chemical while also becoming oxidized, or having its carbonyl carbon converted to a carboxyl group.
• We have to find which one is not a reducing sugar.

Step 2: Explanation (Part a)

• Sucrose is not a reducing sugar. 
• This is because the glycosidic link between glucose's carbon-1 and fructose's carbon-2 cannot open to produce an aldehyde.

Step 3: Glucose units (Part b)

• Although glucose is called a monosaccharide.
• Because it is made up of only one unit, individual sugar units can be connected together to form a chain, much like monomer units can be linked together to produce a lengthy polymer.

Step 4: Explanation (Part b)

• Maltose consists of two glucose molecules.
• Also maltose has a mild sweetness to it, but its primary purpose is digestion. 
• Because most carbohydrates are in an insoluble form, it is critical that they be broken down into smaller pieces.

Step 5: Introduction about milk sugar (Part c)

• Lactose is also referred to as milk sugar
• Lactose is broken down in the colon by lactase, an enzyme, into glucose and galactose, two simpler sugars that our bodies utilize for energy and other purposes.

Step 6: Glucose and fructose (Part d)

• Glucose and fructose are monosaccharides, or simple sugars.
• Sucrose hydrolysis produces glucose and fructose.