Difference between Alpha Glucose and Beta Glucose

Glucose is the most familiar name in the house. It tastes sweet and we often consider it as an energy-giving substance also. Glucose is actually a sugar which has two isomers namely, α-glucose and the β-glucose. These both isomers have their own property.

Sugars come under the category of carbohydrates. There are many kinds of sugars as per the structure of the sugar. It can be monosaccharide, disaccharide and polysaccharides. If we look at the monosaccharides, they contain just one molecule. Dextrose or Glucose is a well-known monosaccharide, fructose and galactose are the other examples of monosaccharide. Disaccharides are the complex structure of sugars, Sucrose and maltose come as the examples of disaccharides. And the third variety known as polysaccharides has the example of starches and cellulose.

The glucose has two isomers, alpha glucose and beta glucose. The main difference between the two lies in the orientation of the (-OH) hydroxyl group. In both cases, the hydroxyl group gets connected to the first carbon atom, just the geometry is different. In the structure of Alpha glucose, the orientation is (1-hydroxyl) and (4-hydroxyl). These both get connected at the same side of the carbon atom. In case of Beta glucose, the orientation is again the (1-hydroxyl) and (4-hydroxyl) , but this time, these both get connected with the carbon atom at the opposite sides of each other. So, both the glucose, alpha glucose and beta glucose have the same structure, just the orientation of the hydroxyl group is different.

Alpha glucose is said to be less stable than that of the beta glucose. The reason behind this is again the orientation of the hydroxyl group. Due to being on the same side, the hydroxyl group creates the steric effect in the alpha glucose. Steric effect is created because of interaction between the nonbonding ones, this interaction impacts and affects the geometry, size and reaction time of the molecules and ions also. Once the steric hindrance is created, it slows down the reaction. Thus, making the alpha glucose less stable. 

Alpha glucose is higher in energy. Although the difference in energy is not much higher but still, a little higher energy is seen in alpha glucose. Alpha glucose has a melting point of 146°C, which is lower than the beta glucose. Alpha glucose is often highly reactive to enzymes, due to which they get easily broken by the enzymes. The delicious parts of plants are very often made up of a series of alpha glucose. As we know, glucose is a monosaccharide that contains one molecule, when the glycosidic bond is formed between two alpha glucoses, it results in making of maltose. If we crystalize alpha glucose, it can be forged only into α-glucopyranose. If we do the polymerisation of the alpha glucose, we get the starch which is a polysaccharide of course. Food items rich in carbohydrates, like potatoes and bread, have a good amount of glucose.

The alpha and beta glucoses are found in the environment in the ratio of 36:64 as per their stability. Due to higher stability, beta glucose is found more in nature. It means if you find 36% alpha glucose, you will find 64% beta glucose at the same place. 

Beta glucose is less in energy. Although the difference in energy is not much lower but still, a little higher energy is seen in alpha glucose. Beta glucose has a melting point of 150°C, which is slightly higher than the Alpha glucose. Beta glucose is often less reactive to enzymes, due to which they do not get easily broken by the enzymes. The hard parts of plants are very often made up of a series of beta glucose. As we know, glucose is a monosaccharide, that means it contains one molecule, when the glycosidic bond is formed between two beta glucoses, it results in the formation of cellobiose. If we crystalise beta glucose, it can be forged into 2 varieties- β-glucopyranose and β-glucopyranose hydrate. If we do the polymerisation of the beta glucose, we get the cellulose, which is a polysaccharide of course. Fibres are said to be a rich source of beta glucose.

Conclusion

By paying attention to the details of difference between the alpha glucose and the beta glucose, we see that the major difference between the two is due to the orientation of the hydroxyl group which in effect brings so many changes in the reactivity, stability and structure of alpha glucose and the beta glucose. With very less significant change in their melting point and energy, they made a huge difference in their existence in the environment.

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