Problem 148 - Advanced Problems in Organic Chemistry for Competitive Examinations

Question

Upon hydrolysis lactose breaks down into (a) glucose and arabinose (b) glucose and fructose (c) glucose and galactose (d) glucose and mannose

Step-by-Step Solution

Answer

Lactose hydrolyzes into glucose and galactose.

Step 1: Understanding Lactose Hydrolysis

Lactose is a disaccharide sugar that is composed of two monosaccharides. The question asks about the products of lactose hydrolysis, which is a chemical reaction where water is used to break down a compound. In this case, the compound is lactose.

Step 2: Identifying the Monosaccharides in Lactose

Lactose is composed of two specific monosaccharides joined together. These monosaccharides are glucose and galactose. Lactose belongs to the group of disaccharides, which are sugars composed of two monosaccharide units.

Step 3: Performing the Hydrolysis Reaction

In a hydrolysis reaction, water breaks the glycosidic bond between the monosaccharides. For lactose, this involves breaking the bond between glucose and galactose. This results in two separate sugar molecules: one glucose molecule and one galactose molecule.

Step 4: Selecting the Correct Answer

From the given options, option (c) glucose and galactose is the correct answer, as these are the monosaccharides formed when lactose undergoes hydrolysis.

Key Concepts

Disaccharide

Disaccharides are types of carbohydrates that consist of two monosaccharide molecules bonded together. They are crucial in living organisms as they often act as energy sources. Common disaccharides include sucrose, maltose, and lactose. In the case of lactose, it is a disaccharide found in milk and dairy products. Lactose is specifically made up of two simple sugar units, or monosaccharides, which are glucose and galactose. Understanding disaccharides is essential for recognizing how body breaks down these sugars during digestive processes.

Monosaccharides

Monosaccharides are the simplest form of carbohydrates and are often referred to as simple sugars. They serve as the building blocks for more complex sugars like disaccharides and polysaccharides. These simple sugars can be absorbed directly into the bloodstream and used by the body for energy. In the context of lactose hydrolysis, glucose and galactose are the two monosaccharides that result from the breakdown of lactose. When you consume lactose, it is these monosaccharides that are ultimately used by your body as a source of energy.

Glycosidic Bond

The glycosidic bond is a type of covalent bond that joins a carbohydrate (sugar) molecule to another molecule, which can be another carbohydrate. In the case of lactose, the glycosidic bond connects glucose and galactose. During the process of hydrolysis, water molecules interact with this bond, effectively breaking it. This cleaving of the glycosidic bond is what separates the disaccharide lactose into its monosaccharide components: glucose and galactose. Understanding glycosidic bonds is fundamental to grasping how larger carbohydrate molecules are synthesized and broken down in biological systems.

Glucose and Galactose

Glucose and galactose are both essential monosaccharides that result from the hydrolysis of lactose. Glucose is a primary energy source for cells and is crucial for cellular respiration. It is involved in several metabolic pathways that keep our body functioning.

• Glucose: Often called 'blood sugar', it is central to many metabolic pathways in the body.
• Galactose: Also a crucial energy source, but less common in the diet compared to glucose.

In the body, galactose can be converted into glucose, which serves to maintain energy levels, especially in the brain. Glucose and galactose's relationship is pivotal in dairy digestion and carbohydrate metabolism.