Problem 74 - A Complete Resource Book in Chemistry for JEE Main

Question

Fucrose molecule is made up of (a) a gluco pyranose an a fructo pyranose (b) a gluco pyranose an a fructo furanose (c) a gluco furanose an a fructo pyranose (d) a gluco furanose an a fructo furanose

Step-by-Step Solution

Answer

Sucrose is made up of a gluco pyranose and a fructo furanose.

Step 1: Understanding the Components of Sucrose

Sucrose is a disaccharide composed of two monosaccharides: glucose and fructose. It is important to identify the structure of these monosaccharides to determine the correct components of a sucrose molecule.

Step 2: Identifying Gluco and Fructo Forms

Glucose can form a cyclic structure known as pyranose when it has a six-membered ring. Gluco pyranose refers to this six-membered ring structure of glucose. Fructose can form a cyclic structure known as furanose when it has a five-membered ring. Fructo furanose refers to this five-membered ring structure of fructose.

Step 3: Determining the Correct Option

Now, we need to identify the combination of gluoc and fructo forms in sucrose. Sucrose is composed of a gluco pyranose (glucose in a pyranose form) and a fructo furanose (fructose in a furanose form). Therefore, the correct option that describes a sucrose molecule is (b) a gluco pyranose and a fructo furanose.

Key Concepts

Disaccharide

Sucrose is a well-known example of a disaccharide. But what exactly is a disaccharide? At its core, a disaccharide is a type of carbohydrate made up of two monosaccharide molecules. Carbohydrates, including disaccharides, are essential for energy production in living organisms.

• Formation: Disaccharides form when two monosaccharides undergo a dehydration reaction. This reaction involves the removal of a water molecule.
• Examples: Other common disaccharides include lactose and maltose.
• Functions: They serve as an important energy source and can be broken down into their monosaccharide components during digestion.

Understanding the structure and formation of disaccharides like sucrose helps comprehend how they contribute to our dietary intake and energy supply.

Monosaccharides

Monosaccharides are the simplest form of carbohydrates. As single sugar molecules, they are the building blocks for more complex carbohydrates such as disaccharides and polysaccharides.

• Types: Common monosaccharides include glucose, fructose, and galactose.
• Structure: Each monosaccharide consists of a carbon backbone, with several hydroxyl groups (-OH) attached, making them quite soluble in water.
• Importance: They are crucial for providing energy. The body uses glucose, for example, as a primary energy source.

Monosaccharides are not just energy sources but also participate in forming the structure of nucleic acids. Their various forms enable them to engage in numerous biological functions.

Glucose and Fructose

Glucose and fructose are two key monosaccharides found in many natural foods. They are also components of the disaccharide sucrose.

• Glucose: Often called blood sugar, it is vital for energy. It is released during the digestion of carbohydrates and is essential for cellular respiration.
• Fructose: Known as fruit sugar, it is found in fruits and honey. It is sweeter than glucose and metabolized differently by the liver.
• Role in Sucrose: In sucrose, glucose and fructose link together to form a disaccharide, providing sweetness to foods like table sugar.

Understanding these sugars helps in grasping how sucrose is structured and their impact on metabolism and energy production.

Pyranose and Furanose Forms

Monosaccharides such as glucose and fructose can form ring structures. These are known as pyranose and furanose forms based on the number of atoms in the ring.

• Pyranose: This structure forms a six-membered ring and is typical for glucose. The name is derived from pyran, a compound with an oxygen atom and five carbon atoms.
• Furanose: This form creates a five-membered ring, seen in fructose. It takes its name from furan, containing four carbon atoms and an oxygen atom.
• Importance in Sucrose: In sucrose, glucose appears as a pyranose and fructose as a furanose, a combination that determines its chemical properties and sweetness.

By understanding these forms, one can see how different sugar structures influence their function and role in food chemistry.