Which of the following is an example of a disaccharide?

December 11, 2025 •

3 min read

Over 90% of all carbohydrates in the human diet come from just a few sources, including cereals, potatoes, and bread, which all contain various forms of sugars. Among these, disaccharides, or double sugars, are a fundamental class of carbohydrates, and common examples include sucrose, lactose, and maltose. This article explores these important sugar molecules and explains how they are formed and utilized by the body.

Quick Summary

This article defines a disaccharide as a carbohydrate composed of two monosaccharides, focusing on common examples like sucrose, lactose, and maltose. It details their formation through dehydration synthesis and explains their digestion process with specific enzymes.

Key Points

Sucrose is an example of a disaccharide: It is formed from a molecule of glucose and a molecule of fructose and is commonly known as table sugar.
Lactose is another common disaccharide: Found in milk and dairy products, it is composed of glucose and galactose.
Maltose is a disaccharide from grains: This sugar is made of two glucose molecules and is found in malted products.
Disaccharides are formed through dehydration synthesis: Two monosaccharides are joined by removing a water molecule, creating a glycosidic bond.
Enzymes are required for digestion: To be absorbed, disaccharides must be broken down into monosaccharides by specific enzymes like sucrase, lactase, and maltase.

Understanding What Makes a Disaccharide

To understand what constitutes a disaccharide, it's crucial to first define its building blocks: monosaccharides. Monosaccharides, or simple sugars, are the most basic unit of carbohydrates and cannot be broken down further. Common examples include glucose, fructose, and galactose. A disaccharide, as the prefix 'di-' suggests, is formed when two monosaccharides join together. This chemical union happens through a process called dehydration synthesis, or a condensation reaction, where a molecule of water is removed. The resulting covalent bond that links the two sugar units is known as a glycosidic bond.

Common Examples of Disaccharides

Three of the most common disaccharides are found in our everyday diet:

Sucrose: Often referred to as table sugar, sucrose is the product of one glucose molecule joining with one fructose molecule. It is naturally found in sugar cane, sugar beet, and many fruits and vegetables.
Lactose: Known as milk sugar, lactose is composed of one glucose molecule and one galactose molecule. As its name implies, it is found in milk and dairy products. A deficiency in the enzyme lactase, which breaks down lactose, leads to lactose intolerance.
Maltose: Maltose, or malt sugar, is made from two glucose molecules linked together. It is formed during the digestion of starch and is found in malted grains, such as barley, and can also be used as a sweetener.

The Importance of Disaccharide Digestion

For the human body to use disaccharides as an energy source, they must be broken down into their individual monosaccharide components. This process, called hydrolysis, involves adding a water molecule to break the glycosidic bond. Specific enzymes, known as disaccharidases, are responsible for this breakdown in the small intestine.

Sucrase breaks sucrose into glucose and fructose.
Lactase breaks lactose into glucose and galactose.
Maltase breaks maltose into two glucose molecules.

The resulting monosaccharides are then absorbed into the bloodstream and transported to cells throughout the body for energy. This enzymatic activity is crucial for nutrient absorption and overall metabolic health.

Disaccharides vs. Monosaccharides

To clarify the differences, a comparison table can be helpful in understanding the key distinctions between these two types of carbohydrates.


Feature	Monosaccharides	Disaccharides
Composition	Single sugar molecule (monomer)	Two monosaccharide units (dimer)
Hydrolysis	Cannot be hydrolyzed into smaller carbohydrates	Can be hydrolyzed into two monosaccharides
Absorption	Absorbed directly into the bloodstream	Must be broken down before absorption
Sweetness	Generally sweet-tasting	Vary in sweetness (e.g., sucrose is sweeter than maltose)
Examples	Glucose, Fructose, Galactose	Sucrose, Lactose, Maltose
Solubility	Highly soluble in water	Generally soluble in water, but less so than monosaccharides

The Role of Glycosidic Bonds

The glycosidic bond is what defines the specific properties of each disaccharide. The type of bond (alpha or beta) and the location of the linkage between the carbon atoms determine the molecule's overall shape and how enzymes interact with it. For instance, humans cannot digest cellulose, a polysaccharide composed of beta-linked glucose units, because they lack the necessary enzyme. In contrast, the alpha linkages in starch and maltose are easily broken down by human digestive enzymes.

Sources of Disaccharides in Food

Understanding where disaccharides are found can help in making informed dietary choices. Sucrose is found in table sugar, honey, and many fruits. Lactose is a key component of all mammalian milk and is present in dairy products like yogurt and cheese. Maltose, in addition to malted beverages, can also be found in certain grains and is a product of starch digestion during brewing and baking.

Conclusion

In summary, the question "Which of the following is an example of a disaccharide?" has several correct answers, including sucrose, lactose, and maltose. These double sugars are formed by the joining of two monosaccharides via a glycosidic bond and must be hydrolyzed by specific enzymes during digestion to be absorbed and utilized by the body for energy. Understanding the chemical composition and digestion of disaccharides is fundamental to grasping how our bodies process carbohydrates and derive energy from the foods we consume. Learning about these basic components of nutrition empowers individuals to make better dietary decisions for their overall health.

For more in-depth scientific explanations on carbohydrate metabolism and function, refer to the resource provided by the National Institutes of Health.

Frequently Asked Questions

A monosaccharide is a single sugar unit, like glucose, while a disaccharide is composed of two monosaccharide units joined together. Disaccharides must be broken down by enzymes before they can be absorbed by the body, whereas monosaccharides can be absorbed directly.

A disaccharide is formed when two monosaccharide molecules join together through a chemical reaction called dehydration synthesis, or condensation. This process involves the removal of a water molecule and results in a glycosidic bond that links the two sugar units.

During digestion, enzymes in the small intestine break down disaccharides into their constituent monosaccharides through hydrolysis. For example, lactase breaks down lactose, and sucrase breaks down sucrose.

Lactose intolerance is caused by a deficiency of the enzyme lactase, which is necessary to break down lactose into glucose and galactose. Without sufficient lactase, the undigested lactose can cause gastrointestinal issues.

Sucrose, or table sugar, is widely found in sugar cane and sugar beet. It is also present in many fruits and vegetables, serving as a primary source of sweetness.

The primary function of disaccharides in the human body is to serve as an energy source. Once broken down into monosaccharides, these simple sugars are absorbed and used by cells for metabolic processes.

Yes, different disaccharides can be formed from the same monosaccharides. For example, both maltose and cellobiose are made from two glucose units, but the difference in their glycosidic linkage (alpha vs. beta) results in distinct molecules with different properties.