Question

The digestion of lactose gives what compounds? Name them.

Short answer

The digestion of lactose produces the monosaccharides glucose and galactose.

Step-by-step solution

Understand the digestion of lactose

Lactose is a disaccharide sugar found in milk which is made up of two monosaccharides, glucose and galactose, linked by a glycosidic bond. In the small intestine, the enzyme lactase breaks down lactose into its constituent sugars.

Identify the products of lactose digestion

Through the activity of lactase, lactose is hydrolyzed or split into its two component sugars. These sugars are glucose and galactose.

Key concepts

Disaccharides

Disaccharides are a type of carbohydrate that consists of two monosaccharide molecules linked together. They are found in various natural sources, such as fruits, vegetables, and, most notably, lactose is found in milk. Disaccharides play an essential role in the human diet, providing a source of energy that is released upon their digestion. When a disaccharide like lactose enters the digestive system, it must be split into its simpler sugar components to be absorbed by the body. This digestive process ensures that the energy contained in the complex sugar is made available for use by the body's cells.

• Lactose, for instance, is a disaccharide composed of glucose and galactose.
• Sucrose, another common disaccharide, is formed by glucose and fructose.
• Maltose, yet another example, consists of two glucose molecules.

The digestion of disaccharides occurs mainly in the small intestine, which is equipped with enzymes specialized for this process.

Monosaccharides

Monosaccharides are the simplest form of carbohydrates and include such sugars as glucose, galactose, and fructose. These single sugar molecules are the building blocks of more complex carbohydrates such as disaccharides and polysaccharides. As the final step in the digestive process for carbohydrates, monosaccharides are readily absorbed into the bloodstream. Their primary role is to supply energy to the body’s cells, and they can either be used directly for energy or stored as glycogen in the liver and muscles for later use.

Energy Source

Monosaccharides provide immediate energy to the cells. For example:

• Glucose is often referred to as blood sugar and is the body's preferred source of energy.
• Galactose, which is less sweet than glucose, is converted into glucose by the liver to be used for energy.
• Fructose, found in fruits, is also converted into glucose by the liver before being utilized as an energy source.

Once absorbed, these simple sugars are indispensable for cellular function, supporting everything from physical activity to cognitive processes.

Lactase Enzyme

The lactase enzyme is a crucial protein that catalyzes the breakdown of lactose into monosaccharides. This enzyme is located on the brush border of the small intestine’s lining. Individuals who are lactose intolerant lack sufficient amounts of lactase, which hinders their ability to digest lactose properly, leading to gastrointestinal discomfort when consuming dairy products.

Enzyme Function

Lactase's primary function is to hydrolyze the glycosidic bond in lactose, allowing the digestion and subsequent absorption of glucose and galactose. The enzyme works optimally at a specific pH and temperature, typical of those found in the small intestine, ensuring efficient lactose processing during digestion.

• For individuals with normal levels of lactase, dairy consumption is usually trouble-free.
• Those lacking lactase may use lactase supplements or consume lactose-free products.

Understanding the role of lactase is vital for addressing dietary challenges related to lactose intolerance and promoting optimal digestion of dairy products.

Glycosidic Bond

A glycosidic bond is a type of covalent link that joins a carbohydrate (sugar) molecule to another group, which can be a carbohydrate or a different type of molecule. In the case of lactose, the glycosidic bond connects the two monosaccharides, glucose and galactose. This bond is sturdy and specific, requiring the precise action of an enzyme to be broken down during digestion.

Bond Breakdown

The glycosidic bond in lactose is broken by the lactase enzyme during the digestion process. Breaking this bond is essential for transforming lactose into digestible units that can be absorbed and utilized by the body.

• The bond type and location can affect the properties of the sugar and its resistance to enzymatic breakdown.
• The enzymatic activity that splits the glycosidic bond is known as hydrolysis.

This understanding of glycosidic bonds is fundamental not only in the digestion of lactose but also in the broader context of carbohydrate chemistry and biology.