What is Maltose?

Maltose is a kind of carbohydrate. Maltose is generated by the combination of two glucose molecules. Glucose has 6 carbons, 6 oxygen and 12 hydrogen elements. The glucose components in maltose are connected head-to-tail by an α-link between the first carbon atom of one molecule of glucose and the next glucose molecule's fourth carbon atom.

Carbohydrates are among the foods that our system needs to work efficiently which is one of the body's primary energy sources. They usually have carbon, hydrogen and oxygen. Maltose is such a carbohydrate which have unavoidable significance.

In growing crop, maltose exists to a certain degree. The breakdown of cellulose and glycogen is the most common cause for its production. The activity of malt (germinating barley) on starch in beer production causes liberation of maltose; this is why it is also called malt sugar. Maltose is about 30 percent as sweet as sucrose. Maltose and any other disaccharide cannot be processed immediately by the human body since the molecules are too massive to go across the cellular membrane of the bowel. Thus, the disaccharide consumed must be divided into its two consisting monosaccharide units by hydrolysis first.

Characteristics of Maltose

Maltose is a reducing sugar molecule. The Maltose occurs in the form of a white crystalline solid. It has 342.30 g·mol−1 molar mass. It melts at 102°C and is water-soluble. Maltose has a generalized formula of C₁₂H₂₂O₁₁, identical to sucrose as well as lactose. However, Maltose is composed of two disaccharide units of glucose. The glucose compounds are combined by the α-1→4 glycosides bond, meaning that the α–anomeric Carbon-1 (C-1) one glucose forms a bond with and the hydroxyl oxygen atom C-4 on the other glucose molecule. Similarly, when the glycosidic binding is β-(1→) the product formed will be cellobiose. while Isomaltose is another maltose isomer. Both consist of two glucose units together connected with a glycosidic bond. The difference between maltose and isomaltose is the glycosidic bond position in maltose is α-1→4 while in isomaltose it is α -1→6.

Structure of Maltose

The oxygen atom which is glycosidic of one of the two glucose molecules in maltose is α bonded and is attached to the C-4 carbon atom of another glucose molecule which is also an aglycone. This causes maltose to be called 1,4′-glycoside. Enzymatic hydrolysis of starch that is catalyzed by the enzyme known as amylase produces maltose. On the other hand, maltase is the enzyme that hydrolyses maltose to give two units of d-glucose at the end of the process. The monosaccharide present on the left side is the α-D-glucopyranosyl hemiacetal. It is linked by α--(1,4′) glucose bond to D-glucopyranose, which is an aglycone. The glycosidic bond oxygen atom is in the middle of the two rings roughly. It is axial and thus positioned downwards. It is connected to C-4 of the aglycone atom and thus the relation is axial and equatorial.

Due to its hemiacetal nature of the aglycone, maltose undergoes mutarotation. Maltose is also a reducing sugar for the same reasons. Benedict's solution will react to the free aldehyde produced by the ring opening. The "non-reducing end" of the disaccharide is considered the acetal portion of the structure. The anomeric hemiacetal point of the maltose is where it undergoes mutarotation. The IUPAC name of maltose is given as 4-O-(a-d-glucopyranosyl)-b-d-glucopyranose which means that the glucose molecule that is present on the left is responsible for the acetal segment of the glycosidic linkage. The word “pyrano” refers to the six-atom ringed structure. Whereas, the suffix “osyl” is used to specify that the ring structure is connected to a glycosidic linkage while the 4-O prefix indicates the location of the oxygen atom present on the right-hand ring structures aglycone. Lastly, the term b-d-glucopyranose is used to tell us more about the aglycone.

Difference between Maltose, Lactose and Sucrose

Three major food disaccharides are maltose (malt sugar), lactose (milk sugar), and sucrose (common table sugar). The carbohydrates have a chemical composition that is the same which is C₁₂H₂₂O₁₁. All 3 have a component of glucose. In maltose, the compound consists of two glucose molecules. In the case of lactose and sucrose, they have one glucose unit which combines with another molecule. For lactose, glucose is linked to the galactose unit whereas for sucrose a glucose molecule is attached to a fructose molecule. In maltose, the glycosidic bond α-(1,4) occurs between carbon-1 and carbon-4 of the two sugar molecules. For lactose, the bonding is β-(1,4) glycosidic linkage that occurs between C-1 of galactose and C-4 of glucose. While for sucrose the glycosidic linkage is formed between glucose Carbon-1 and fructose Carbon-2.

Biological Importance of Maltose

One of the major dietary suppliers of glucose is maltose. Since it is mostly involved in energy synthesis, glucose is an essential resource. Glucose is the most widespread type of monosaccharide used by cells to generate ATP by phosphorylation of substrates and/or oxidative phosphorylation (glycolysis) including redox reactions and also chemiosmosis. Starch produces maltose. Starch, as well as maltose in the context that they have been made up of glucose groups, are architecturally identical. But starch is a glucose polymer, while maltose would be a glucose disaccharide. Maltose is utilized commonly as a sweetener, also as a mineral in bacteriological culture medium, and as baby feed. Sometimes it is also used in baked pastries. It causes a rise in the bread dough when carbon dioxide is generated and emitted by combining starch with enzymes during the transformation of starch into maltose. It is less sweet than most traditional sugars. However, because of its high glycemic index, maltose intake is not recommended for diabetic patients.

Practice Problems

Hydrolysis of maltose will result in which monosaccharides: glucose, fructose or galactose

Solution:

Hydrolysis of maltose will give us two molecules of glucose.

Common Mistakes

The most common mistake students can make is while differentiating between maltose, lactose and sucrose. The glycosidic linkage should b identified carefully while naming a structure.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for

• B.Sc. in Chemistry, Biotechnology, Biochemistry and Biology
• M.Sc. in Chemistry, Biotechnology, Biochemistry and Biology