Which of the following carbohydrates is classified as a disaccharide?

January 13, 2026 •

3 min read

Carbohydrates are the most abundant of the four major biomolecules, converting over 100 billion metric tons of carbon dioxide and water into usable compounds each year. This article will clarify which of the following carbohydrates is classified as a disaccharide and provide a comprehensive overview of carbohydrate types.

Quick Summary

This article defines disaccharides as double sugars composed of two monosaccharide units and highlights sucrose, lactose, and maltose as prime examples. It contrasts them with single-unit monosaccharides like glucose and multi-unit polysaccharides such as starch and glycogen, detailing their structures, functions, and dietary sources.

Key Points

Disaccharides Defined: Disaccharides are double sugars formed when two monosaccharide units join via a glycosidic bond.
Common Disaccharide Examples: Sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose) are the most common disaccharides.
Monosaccharides vs. Disaccharides: Monosaccharides are single sugar units like glucose and fructose, while disaccharides are two-unit sugars.
Polysaccharides Defined: Polysaccharides are complex carbohydrates made of long chains of many monosaccharide units, such as starch and glycogen.
Function of Disaccharides: Disaccharides serve as an energy source, which the body breaks down into simpler monosaccharides for absorption and metabolism.

Understanding Carbohydrate Classification

Carbohydrates are a major class of biomolecules categorized based on the number of simple sugar units, or saccharides, they contain. The three main categories are monosaccharides, disaccharides, and polysaccharides. A disaccharide, also known as a 'double sugar', is formed when two monosaccharide units join together via a glycosidic bond in a dehydration reaction. To identify which carbohydrate is classified as a disaccharide, it is crucial to understand the characteristics and examples of each class.

Monosaccharides: The Simplest Sugars

Monosaccharides are the basic building blocks for all other carbohydrates and cannot be hydrolyzed into simpler sugars. Their general chemical formula is CnH2nOn. Examples of monosaccharides include:

Glucose: The most common and abundant monosaccharide, often called blood sugar. It is a primary energy source for the body and the brain.
Fructose: A fruit sugar found in fruits, root vegetables, and honey, known for being the sweetest of the natural sugars.
Galactose: A sugar found in milk, where it combines with glucose to form lactose.

Disaccharides: The Double Sugars

Disaccharides are formed by combining two monosaccharides. The three most common disaccharides are sucrose, lactose, and maltose.

Sucrose: Also known as table sugar, sucrose is a non-reducing sugar formed by the combination of one glucose molecule and one fructose molecule. It is extracted from plants like sugar cane and sugar beets and is widely used as a sweetener.
Lactose: Found in milk, lactose is formed by a bond between one glucose molecule and one galactose molecule. For digestion, it is broken down by the enzyme lactase, which some individuals lack, leading to lactose intolerance.
Maltose: Known as malt sugar, maltose is formed from two glucose molecules. It is a reducing sugar and is a product of the enzymatic breakdown of starch.

Polysaccharides: The Complex Carbohydrates

Polysaccharides are complex carbohydrates made up of long chains of many monosaccharide units joined together by glycosidic linkages. They serve as energy storage or structural components in organisms.

Starch: The storage polysaccharide for energy in plants, it consists of two polymers of glucose units: amylose and amylopectin.
Glycogen: The storage form of glucose in animals, found primarily in the liver and muscles. It is a highly branched polymer of glucose.
Cellulose: A structural polysaccharide composed of linear chains of glucose units, it is the main component of plant cell walls. Humans cannot digest cellulose.

Disaccharide vs. Monosaccharide and Polysaccharide


Feature	Monosaccharides	Disaccharides	Polysaccharides
Number of Units	One simple sugar unit	Two monosaccharide units	Ten or more monosaccharide units
Hydrolysis	Cannot be hydrolyzed into smaller sugars	Hydrolyzed into two monosaccharides	Hydrolyzed into many monosaccharides
Examples	Glucose, Fructose, Galactose	Sucrose, Lactose, Maltose	Starch, Glycogen, Cellulose
Solubility in Water	Highly soluble	Generally soluble, but less so than monosaccharides	Poorly soluble or insoluble
Function	Immediate energy source for cells	Energy source after digestion into monosaccharides	Energy storage and structural support

Dietary Sources of Disaccharides

Disaccharides are common in many food sources, providing an energy source for the body. When consumed, the body breaks them down into monosaccharides for absorption and energy use. For example, the lactose in milk is broken down into glucose and galactose, while the sucrose in table sugar is broken down into glucose and fructose. Plants also utilize disaccharides, like sucrose, to transport energy from one cell to another.

Conclusion

To answer the question, sucrose, lactose, and maltose are carbohydrates classified as disaccharides. By understanding the key differences between monosaccharides, disaccharides, and polysaccharides, one can better grasp the fundamental building blocks of carbohydrates. Monosaccharides are single units, disaccharides are double units, and polysaccharides are many units linked together, all serving distinct roles in biology as energy sources or structural components. Recognizing these differences is essential for anyone studying biochemistry or nutrition.

For more information on the chemical structure of these compounds, resources like this Taylor & Francis article provide a deeper dive.

Frequently Asked Questions

A monosaccharide is the simplest form of carbohydrate, consisting of a single sugar unit (e.g., glucose). A disaccharide is composed of two monosaccharide units linked together, such as sucrose or lactose.

Sucrose is a disaccharide. It is formed from one molecule of glucose and one molecule of fructose bonded together.

Lactose, or milk sugar, is a disaccharide formed by the condensation of one molecule of glucose and one molecule of galactose.

Maltose is a disaccharide composed of two glucose molecules joined together. It is often referred to as malt sugar.

The body breaks down disaccharides into their constituent monosaccharides through a process called hydrolysis, which is catalyzed by specific enzymes like sucrase, lactase, and maltase.

Most disaccharides are soluble and have a sweet taste, which is why they are often referred to as sugars. However, the level of sweetness can vary between different disaccharides, as can their solubility.

Disaccharides primarily serve as an energy source for the body. They are broken down into monosaccharides, which can then be used for cellular energy or stored for later use.