Question

Complete hydrolysis of cellulose gives (a) D-fructose (b) D-glucose (c) D-ribose (d) L-glucose

Short answer

Cellulose completely hydrolyzes to D-glucose.

Step-by-step solution

Understanding Cellulose

Cellulose is a polysaccharide composed of glucose units. Its structure consists of long chains of D-glucose linked by beta-1,4-glycosidic bonds.

Defining Hydrolysis

Hydrolysis is a chemical process in which a molecule splits into two parts by the addition of a water molecule. In the context of cellulose, hydrolysis breaks the glycosidic bonds between glucose units.

Identifying the Products of Cellulose Hydrolysis

When cellulose is completely hydrolyzed, the glycosidic bonds are cleaved, releasing the individual sugar units that make up cellulose.

Determining the Product of Complete Hydrolysis

Since cellulose is made entirely of D-glucose units, the complete hydrolysis of cellulose yields D-glucose as the end product.

Key concepts

D-glucose

D-glucose is a simple sugar and a fundamental building block in many carbohydrates. It is a type of glucose that has its hydroxyl group on the right side when drawn in a Fischer projection, hence the "D" designation. D-glucose is crucial for energy production in most living organisms.

When cellulose, a polysaccharide, undergoes hydrolysis, the chains of glucose are broken down, releasing D-glucose. This molecule is essential not only due to its role as an energy source but also because it serves as a precursor to many biochemical substances. Understanding D-glucose is vital when studying metabolic pathways and processes where sugars are involved.

• D-glucose is a hexose sugar, meaning it contains six carbon atoms.
• It plays a significant role in cellular respiration, providing energy to cells.
• D-glucose is often called blood sugar as it circulates in the bloodstream of animals.

Polysaccharides

Polysaccharides are complex carbohydrates formed by long chains of monosaccharide units bonded together. In cellulose, the polysaccharide chains consist of repeated D-glucose units linked by beta-1,4-glycosidic bonds.

These molecules are crucial for various biological functions, serving as energy storage or structural components in cells. Different polysaccharides have diverse structures and functions, such as cellulose in plants or glycogen in animals.

• Polysaccharides can be linear or branched, influencing their properties and functions.
• They play a role in dietary fiber, impacting digestion and gut health.
• The complete hydrolysis of polysaccharides like cellulose converts them into simpler sugars, such as D-glucose.

Beta-1,4-glycosidic bonds

Beta-1,4-glycosidic bonds are specific linkages between sugar molecules, particularly D-glucose units, in polysaccharides like cellulose. These bonds are formed between the first carbon atom of one glucose molecule and the fourth carbon of the next. The 'beta' indicates the specific orientation of these bonds, resulting in a straight, fibrous structure.

Understanding beta-1,4-glycosidic bonds is crucial when studying cellulose's rigidity and strength. These bonds form linear chains that contribute to the structural support in plants, such as the wood and dietary fibers.

• Beta-1,4-glycosidic bonds provide cellulose with its tensile strength, making it suitable for forming strong structures like plant cell walls.
• The rigidity of these bonds also impacts the ability of enzymes to break them down during hydrolysis.
• The breakage of beta-1,4-glycosidic bonds is a key step in the hydrolysis of cellulose into D-glucose.

Chemical process of hydrolysis

The chemical process of hydrolysis involves the decomposition of complex molecules into simpler ones by the addition of water. In the case of cellulose hydrolysis, water molecules penetrate the beta-1,4-glycosidic bonds between the D-glucose units, breaking these linkages to release individual glucose molecules.

Hydrolysis is essential not only in cellulose digestion but also in various biological and chemical processes. It allows organisms to access stored energy or reorganize and recycle biological molecules.

• Hydrolysis reactions are catalyzed by enzymes such as cellulase, which specifically target cellulose.
• It is a reversible reaction, though in biological contexts, it often proceeds in the direction of breaking down complex molecules.
• This process is fundamental in nature for the decomposition of organic matter, releasing nutrients and energy.