Disaccharides - Online Tutor, Practice Problems & Exam Prep

A disaccharide consists of two monosaccharides linked by a glycosidic bond. Common disaccharides include maltose (α-1,4 linkage from two glucose), cellobiose (β-1,4 linkage from glucose), lactose (β-1,4 linkage from glucose and galactose), and sucrose (α-1,β-2 linkage from glucose and fructose). Maltose is found in beer, cellobiose in honey, lactose in milk, and sucrose is table sugar. Human digestion of these sugars varies, with lactose requiring the enzyme lactase, which some individuals lack, leading to lactose intolerance.

Types of Disaccharides Concept 1

Now remember, a disaccharide is when we have two monosaccharides connected to each other by glycosidic linkage. We're going to say there are different types of disaccharides. We're going to say many disaccharides exist, but the most common ones are maltose, cellobiose, lactose, and sucrose. If we take a look here at this chart, we have the two types of sugars that are involved in the creation of this particular common disaccharide. We then talk about the type of linkage that it contains, whether it be alpha or beta, or a combination of the two. Then we talk about what's the name of the disaccharide. And then finally some common examples that might contain this disaccharide. If we take a look at the first one, we have D-glucose plus D-glucose. They together are going to give me an alpha-1,4 linkage. When we have two D-glucose molecules giving us an Alpha 1,4 linkage, this gives us maltose as our disaccharide. And here we have an example of barley. Now, maltose you can find in different types of beer, hops, barley, these are important ingredients that help to create different types of beer.

Now, next, we again have D-glucose and D-glucose. But what's going on here? Well, the first one dealt with alpha-1,4, and now we're dealing with beta-1,4. So the linkage here is different. In this case, this would give us cellobiose. Now, here we have a jar of honey. Honey itself is digestible by us, but it contains trace amounts of this particular disaccharide. So this is a common everyday food that has little bits of this particular type of disaccharide present within it.

Now, next we see that D-glucose is still involved. D-glucose kind of forms a foundation for a lot of these disaccharides. So now we have D-glucose, but instead of having two D-glucose, we're going to have D-galactose involved. So here we're going to say, D-galactose plus D-glucose is going to give us here, a Beta 1,4 linkage, and that's going to give us Lactose as our Disaccharide. Lactose, a great example, milk. Milk sugar is lactose. Now, typically human beings can't digest beta linkages, but we as human beings have lactase as an enzyme within ourselves that helps us to break down this milk sugar. Those of us who are lactose intolerant, who can't digest dairy very well, it's because we have very little of this enzyme or over time it degrades, and we just don't have a lot of it to help us process milk and other types of dairy products.

Now next, again we have D-glucose as our base, and we're going to have it reacting with D-fructose. This would help us to create sucrose. Sucrose here. Sucrose is table sugar. And remember, we've talked about sucrose. Sucrose is very different from other disaccharides. Here it has both an alpha and beta linkage. It would be alpha-1 and beta-2 linkage. So these are our four most common types of disaccharides, and these are some common everyday examples that contain some of these common types of disaccharides.

Types of Disaccharides Example 1

Here in this example, it says, which of the following contains galactose as one of the sugar subunits? Alright. So first of all, glucose is out because glucose is a monosaccharide. It's not going to have another monosaccharide as a subunit. The same thing with ribose, it's a monosaccharide. This leaves either maltose, lactose, or cellobiose. Maltose and cellobiose are out because both of them have d-glucose as their subunits. Where I say here that maltose would have them as an Alpha 1-4 linkage, and this one would have it as a Beta 1-4 linkage. This leaves d as our only answer. Lactose possesses d-glucose and d-galactose that together form a Beta 1-4 linkage. Remember, lactose or milk sugar is a common type of disaccharide.

Which disaccharide forms a 1,1-glycosidic linkage?

• A. Lactose
• B. Maltose
• C. Trehalose
• D. Sucrose
• E. Cellulose

What is the identity of the disaccharide below?

• A. Cellulose
• B. Sucrose
• C. Lactose
• D. Maltose
• E. Cellobiose

Here’s what students ask on this topic:

What are the common types of disaccharides and their sources?

Common disaccharides include maltose, cellobiose, lactose, and sucrose. Maltose, formed from two glucose molecules with an α-1,4 linkage, is found in beer, hops, and barley. Cellobiose, also from two glucose molecules but with a β-1,4 linkage, is present in trace amounts in honey. Lactose, composed of glucose and galactose with a β-1,4 linkage, is the sugar found in milk. Sucrose, made from glucose and fructose with an α-1,β-2 linkage, is commonly known as table sugar. These disaccharides are prevalent in everyday foods and beverages.

How are disaccharides formed and what types of linkages do they have?

Disaccharides are formed by the linkage of two monosaccharides through a glycosidic bond. Maltose is formed from two glucose molecules with an α-1,4 linkage. Cellobiose is also formed from two glucose molecules but with a β-1,4 linkage. Lactose is composed of glucose and galactose with a β-1,4 linkage. Sucrose is made from glucose and fructose with an α-1,β-2 linkage. These linkages determine the properties and digestibility of the disaccharides.

What is lactose intolerance and what causes it?

Lactose intolerance is the inability to digest lactose, the sugar found in milk, due to a deficiency in the enzyme lactase. Lactase breaks down lactose into glucose and galactose, which can be absorbed by the body. Individuals with low levels of lactase experience symptoms like bloating, gas, and diarrhea when consuming dairy products. This condition can be genetic or develop over time as lactase production decreases with age.

What is the difference between maltose and sucrose?

Maltose and sucrose are both disaccharides but differ in their monosaccharide components and linkages. Maltose consists of two glucose molecules linked by an α-1,4 glycosidic bond. It is commonly found in beer, hops, and barley. Sucrose, on the other hand, is composed of glucose and fructose linked by an α-1,β-2 glycosidic bond. Sucrose is commonly known as table sugar and is widely used as a sweetener in various foods and beverages.

How does the human body digest disaccharides?

The human body digests disaccharides by breaking them down into their monosaccharide components using specific enzymes. For example, maltase breaks down maltose into two glucose molecules, lactase breaks down lactose into glucose and galactose, and sucrase breaks down sucrose into glucose and fructose. These monosaccharides are then absorbed into the bloodstream through the small intestine. The efficiency of this process depends on the presence and activity of these enzymes.