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Difference Between Alpha and Beta Glucose

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Last updated date: 12th Jul 2024
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An Introduction to Glucose Molecules: Alpha Vs Beta Glucose

Lets us understand the structure, function, and types of Glucose molecule before analysing the difference between Alpha and Beta Glucose.


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Definition of Glucose

With the chemical formula C₆H₁₂O₆, glucose is a type of sugar. Monosaccharides are a subclass of carbohydrates, and glucose is by far the most prevalent of them all. In order to manufacture cellulose, the most prevalent carbohydrate in the world, glucose is primarily produced by plants and the majority of algae during photosynthesis from water and carbon dioxide with the help of solar energy.


Functions of Glucose

Among all organisms, glucose is the most significant source of energy for energy metabolism. For metabolic use, glucose is stored as a polymer, mostly as starch and amylopectin in plants and glycogen in mammals. Animals' blood contains glucose, which is also known as blood sugar. The stereoisomer of glucose, l-glucose, is created synthetically in relatively tiny quantities and is less physiologically active than d-glucose, which occurs naturally.


Types of Glucose

  • D-Glucose

  • Beta-D-Glucopyranose 

  • Alpha-D-Glucopyranose

What is Alpha and Beta Glucose?

Alpha Glucose: 

Alpha(D) glucose is an isomer of dextrose(D) glucose having hydroxyl (-OH) groups in the 1 and 4 positions on the identical sides of the plane. It is also known as an orientation where the (-CH₂OH) group is on the side of the hydroxyl group in the first position. Due to the hydroxyl groups' steric hindrance on the same sides as this isomer glucose, it is less stable than beta(D) glucose.


Properties of Alpha Glucose

There is a 36% excess of alpha glucose in nature. Alpha glucose is often more reactive than beta glucose because of the location of the hydroxyl group, which has a significant impact on the characteristics of molecules. It has a specific rotation of 112.2° and a melting point of 146°C. Additionally, it can crystallise as  alpha-glucopyranose from its aqueous solution.


Beta Glucose: 

Another isomer of dextrose(D) glucose is beta glucose. It may be recognised by its 1 and 4-position hydroxyl (-OH) groups, which are located on opposing sides. The hydroxyl group of position 1 is located on the same side as (-CH₂OH).


Properties of Beta Glucose

Due to less steric hindrance when the bulky groups are separated from one another, the beta glucose isomer is more stable than the alpha glucose isomer. As a result, beta glucose has a 64% natural abundance. Beta glucose has a specific rotation of 18.7° and a melting point of 150 °C. From the aqueous solutions, beta glucose may be crystallized as beta-glucopyranose and beta-glucopyranose hydrate.


Alpha and Beta Glucose Difference 

S.No

Category

Alpha Glucose

Beta Glucose


Definition

1 and 4 hydroxyl groups are located on the same side.

1 and 4 hydroxyl groups are located on the opposite side. 


Energy levels

Alpha glucose has high energy.

Beta glucose has low energy.


Stability

Alpha glucose has low stability. 

Beta glucose has high stability. 


Melting Point

146⁰C

150⁰C


Polymerisation

Results in the formation of starch. 

Results in the formation of cellulose. 


Specific Rotation

112.2⁰

18.7⁰


Sources

Beans, Corn, Sucrose, Potato

Algae, Mushroom, Legumes, Nuts


Summary

The sole chemical difference between alpha and beta glucose is the orientation of the -OH (hydroxyl) and -H (hydrogen) groups on carbon 1. Unlike beta glucose, which has its -OH group attached above the ring, alpha glucose has its -OH group linked below the ring.

FAQs on Difference Between Alpha and Beta Glucose

1. What are the Characteristics of Alpha Glucose?

The initial carbon atom of the isomer of D-glucose known as alpha glucose has a -OH group on the same side as the -CH₂OH group. Alpha glucose is sugar. Alpha glucose has four -OH groups connected to the primary carbon chain and has a cyclic structure when seen in the context of the chair conformation structure. An "Oxygen bridge" is generated to create the cycle. This indicates that an oxygen atom connects two carbon atoms at the terminal of the major carbon chain.

2. What are the Characteristics of Beta Glucose?

The opposing faces of the 1 and 4 positioned hydroxyl groups are seen in the beta dextrose glucose [Beta-D glucose] chair conformation. Beta glucose is the monomer of cellulose fibers. These fibers are linear because of the beta acetal connections in beta glucose. These glucose monomers are also known as acetal if they have undergone the proper protonation. Hemieacetal structures can be created through the cyclization of D-glucose monomers. These hemiacetals can combine with other alcoholic groups to generate acetals when the environment is acidic.

3. Explain Alpha and Beta Glucose.

Among the numerous glucose isomers, D-glucose is the one that is both the most stable and plentiful. There are two separate types of D-glucose, known as alpha glucose and beta glucose when taking the chair conformation into consideration. The placement of the -OH group on the first carbon atom of alpha and beta glucose is the primary distinction between them. Simple sugars include alpha and beta glucose. Their chemical structures both contain four -OH groups. Except for the -OH group at the first carbon, all -OH groups have an identical spatial arrangement. The aqueous solutions of both can be crystallised. Because chiral carbons are present, both sugars are optically active.