Problem 17 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Complete hydrolysis of starch gives : (a) glucose only [Main Online April 10, 2015] (b) galactose and fructose in equimolar amounts (c) glucose and galactose in equimolar amounts (d) glucose and fructose in equimolar amounts

Step-by-Step Solution

Answer

Option (a) is correct: glucose only.

Step 1: Understand the composition of starch

Starch is a carbohydrate that consists of numerous glucose units linked together. It is a polysaccharide, and its hydrolysis involves breaking these long chains into simpler sugars.

Step 2: Identify the end product of starch hydrolysis

During the hydrolysis of starch, the complex chains of glucose are broken down, ultimately resulting in glucose molecules. Since starch is purely made up of glucose monomers, the complete hydrolysis of starch will yield glucose only.

Step 3: Analyze given options against known product

Given the breakdown of starch results in glucose only, let's analyze each option: - Option (a) suggests glucose only, which is consistent with the known product of starch hydrolysis. - Options (b), (c), and (d) mention other sugars like galactose and fructose, which are not part of the hydrolysis process of starch.

Step 4: Conclusion

Based on the analysis, option (a), which states "glucose only," is correct since complete hydrolysis of starch results in glucose only.

Key Concepts

Polysaccharides

Polysaccharides are long chains of carbohydrate molecules. These are composed of numerous simple sugars called monosaccharides linked together. Starch is a prominent example of a polysaccharide. It is made up of thousands of glucose units that are joined by glycosidic bonds.

The main function of polysaccharides is to store energy and provide structural support. In plants, starch acts as an energy reservoir, whereas in animals, glycogen performs a similar function. The structural role is vividly seen in the form of cellulose in plant cell walls.

• Starch stores energy in plant seeds and roots.
• Cellulose provides structure and rigidity to plant cells.
• Glycogen serves as stored energy in animal liver and muscle cells.

Understanding polysaccharides is crucial because they serve as potential energy sources. When they're broken down, they release simple sugars that can be used for energy by living organisms.

Monosaccharides

Monosaccharides are the simplest form of carbohydrates and are fundamental for living organisms. These are simple sugars that cannot be broken down into smaller sugar units. The most common examples include glucose, fructose, and galactose. They play a vital role in providing energy, as they can be directly used by cells.

Glucose is perhaps the most well-known monosaccharide, used extensively by cells as a primary source of energy. Fructose is naturally found in fruits, while galactose is a part of lactose, the sugar found in milk. These sugars can be absorbed directly into the bloodstream.

• Monosaccharides are the building blocks of carbohydrates.
• They are easily absorbed and metabolized by the body.
• They are essential for processes like cellular respiration.

In the process of starch hydrolysis, like in our original exercise, the polysaccharide starch is broken down into individual glucose monosaccharides. This transformation is essential for making the stored energy in starch readily accessible and usable by our bodies.

Glucose Production

The production of glucose involves breaking down complex carbohydrates into simpler sugars. Starch hydrolysis is a prime example. During this process, enzymes help to break the long chains of glucose units in starch into single glucose molecules. Complete hydrolysis transforms starch entirely into glucose, providing a pure source of this energy-rich sugar.

This process is vital because glucose is a key energy source for almost all living organisms. It is utilized in cellular respiration and various metabolic pathways to form energy-rich molecules like ATP.

• Starch is hydrolyzed to release energy-rich glucose.
• Enzymes like amylase facilitate this process.
• Glucose is used by cells to generate ATP.

The understanding of glucose production through hydrolysis aligns with the conclusion where complete starch hydrolysis results exclusively in glucose. This simple sugar then fuels numerous biological processes essential for maintaining life.