NCERT Class 12 Chemistry Chemistry-II: Chapter 5 — 1 10.1 10.1 10.1 10.1 Carbohydrates Carbohydrates Carbohydrates Carbohydrates Carbohydrates
This chapter, Biomolecules, from NCERT Class 12 Chemistry-II, delves into the complex organic molecules that constitute living systems. It explains the characteristics and classification of key biomolecules like carbohydrates, proteins, and nucleic acids. Carbohydrates are defined chemically as optically active polyhydroxy aldehydes or ketones, or their derivatives. They are classified based on their hydrolysis behavior into monosaccharides, oligosaccharides, and polysaccharides. The chapter also touches upon reducing and non-reducing sugars and introduces monosaccharides like glucose. Understanding these biomolecules is crucial for comprehending the molecular logic of life processes and their role in biosystems, essential for CBSE curriculum.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 12 |
| Subject | Chemistry |
| Book | Chemistry-II |
| Chapter | Chapter 5 — 1 10.1 10.1 10.1 10.1 Carbohydrates Carbohydrates Carbohydrates Carbohydrates Carbohydrates |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 786 |
Learning outcomes
- Explain the characteristics of biomolecules like carbohydrates, proteins, and nucleic acids.
- Classify carbohydrates, proteins, and nucleic acids based on their structures.
- Differentiate between DNA and RNA.
- Describe the role of biomolecules in biological systems.
Vocabulary
| Word | Meaning |
|---|---|
| Biomolecules | Complex organic molecules that constitute living systems. |
| Carbohydrates | Optically active polyhydroxy aldehydes or ketones, or compounds that produce them on hydrolysis. |
| Monosaccharides | Carbohydrates that cannot be hydrolysed further into simpler polyhydroxy aldehyde or ketone units. |
| Oligosaccharides | Carbohydrates that yield two to ten monosaccharide units on hydrolysis. |
| Polysaccharides | Carbohydrates that yield a large number of monosaccharide units on hydrolysis. |
| Sugars | Carbohydrates that are sweet in taste. |
| Saccharides | Another term for carbohydrates, derived from the Greek word for sugar. |
| Reducing sugars | Carbohydrates that reduce Fehling's solution and Tollens' reagent. |
| Non-reducing sugars | Carbohydrates that do not reduce Fehling's solution and Tollens' reagent. |
| Aldose | A monosaccharide containing an aldehyde group. |
| Ketose | A monosaccharide containing a keto group. |
| Glucose | A common monosaccharide, an aldohexose, found freely in nature. |
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Practice questions
- What is the general formula for carbohydrates? Answer: The general formula for carbohydrates is Cx(H2O)y.
- Define monosaccharides. Answer: A monosaccharide is a carbohydrate that cannot be hydrolysed further to give simpler units of polyhydroxy aldehydes or ketones.
- Give examples of oligosaccharides. Answer: Examples of oligosaccharides include disaccharides like sucrose and maltose.
- What are polysaccharides? Answer: Polysaccharides are carbohydrates that yield a large number of monosaccharide units on hydrolysis, such as starch and cellulose.
- What is the difference between an aldose and a ketose? Answer: An aldose is a monosaccharide with an aldehyde group, while a ketose is a monosaccharide with a keto group.
Practice MCQs
Q1. Which of the following is NOT a carbohydrate?
Explanation: Acetic acid (CH3COOH) fits the general formula Cx(H2O)y but is not classified as a carbohydrate. Glucose, sucrose, and starch are all carbohydrates.
Q2. Carbohydrates that yield two to ten monosaccharide units on hydrolysis are called:
Explanation: Oligosaccharides are defined as carbohydrates that yield between two and ten monosaccharide units upon hydrolysis.
Q3. Which of the following is a common example of a monosaccharide?
Explanation: Fructose is a monosaccharide. Sucrose and maltose are disaccharides, and cellulose is a polysaccharide.
Q4. What are carbohydrates that reduce Fehling's solution and Tollens' reagent called?
Explanation: Carbohydrates that possess the ability to reduce Fehling's solution and Tollens' reagent are known as reducing sugars.
Q5. Glucose is an example of a:
Explanation: Glucose contains an aldehyde group and is classified as an aldose. It is a monosaccharide.
Q6. Which term refers to carbohydrates that are sweet in taste?
Explanation: Carbohydrates that have a sweet taste are commonly referred to as sugars.
Frequently asked questions
What are biomolecules?
Biomolecules are complex organic molecules like carbohydrates, proteins, and nucleic acids that make up living systems and are essential for life processes.
How are carbohydrates classified?
Carbohydrates are classified based on their behavior on hydrolysis into monosaccharides (cannot be hydrolysed further), oligosaccharides (yield 2-10 monosaccharide units), and polysaccharides (yield many monosaccharide units).
What is the difference between a monosaccharide and a polysaccharide?
A monosaccharide is the simplest unit of a carbohydrate that cannot be broken down further, while a polysaccharide is a complex carbohydrate made up of many monosaccharide units linked together.
Are all carbohydrates sweet?
No, carbohydrates that are sweet in taste are called sugars (like sucrose and glucose). Polysaccharides like starch and cellulose are not sweet and are called non-sugars.
What is a reducing sugar?
A reducing sugar is a carbohydrate that can reduce Fehling's solution and Tollens' reagent. All monosaccharides are reducing sugars.
What is glucose chemically?
Chemically, glucose is an optically active polyhydroxy aldehyde, specifically an aldohexose.
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NCERT Class 12 Chemistry — Chemistry-II — Chapter 5 — Chemistry Carbohydrates. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.