Question Video: Stating the Reaction that Occurs to Break the Bond between Two Monosaccharides | Nagwa Question Video: Stating the Reaction that Occurs to Break the Bond between Two Monosaccharides | Nagwa

Question Video: Stating the Reaction that Occurs to Break the Bond between Two Monosaccharides Biology • First Year of Secondary School

What type of reaction involves the addition of water to break the bond between two monosaccharides?

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Video Transcript

What type of reaction involves the addition of water to break the bond between two monosaccharides?

This question is asking about the bond between two monosaccharides. To answer the question correctly, let’s review the key points about monosaccharides and disaccharides.

Carbohydrates are molecules composed mainly of carbon and water. Carbo- means carbon, and “hydrate” means water. The most basic building block of carbohydrates is the monosaccharide, mono- meaning one and “saccharide” meaning sugar.

The proportion of the carbons, hydrogens, and oxygens in a monosaccharide usually follow the ratio (CH2O)𝑛, where 𝑛 is a number between three and seven. Examples of monosaccharides are glucose, fructose, and galactose. Two monosaccharides can join together to form a disaccharide, di- meaning two. Examples of disaccharides are lactose made up of glucose and galactose, sucrose made up of glucose and fructose, and maltose made up of two glucose molecules. But how do these monosaccharides join together?

Bonds, called glycosidic bonds, must form between the individual monomers in an enzyme-catalyzed reaction. To understand how this happens, we need to look at the general structure of a monosaccharide, and we will use glucose as an example.

Glucose is a hexose, hex- meaning six. So its formula is C6H12O6, and its structure looks like this. We can label the carbons one to six as shown here. When maltose is formed, two glucose molecules join together. The glycosidic bond forms between carbon one of the first glucose and carbon four of the second glucose molecule. A molecule of water is lost, and so this reaction is called a condensation reaction.

Now that we have seen how the monosaccharides are joined together, let’s look at how they are broken apart. The reaction that formed this maltose molecule can be reversed to form two glucose molecules by breaking the glycosidic bond holding them together. Seeming as water was lost when the bond was formed, it makes sense that water needs to be added to break the bond apart. The name of this reaction is a hydrolysis reaction, hydro- meaning water and “lysis” meaning to split. Again, it is an enzyme-catalyzed reaction.

Having reviewed these key facts, let’s return to the question. We now know that the type of reaction that involves the addition of water to break the bond between two monosaccharides is called a hydrolysis reaction.

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