Do glucose, galactose and fructose have the same properties?
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Carbohydrates are the major components of all living organisms. Glucose and galactose are carbohydrates. Monosaccharides are the building blocks of larger carbohydrate molecules. The main difference between Glucose and Galactose is the position of each hydroxyl group in the 4th carbon; the position of hydroxyl group (-OH) in the 4th carbon is horizontal in the chair confirmation of the Glucose whereas the position of hydroxyl group (-OH) in the 4th carbon is upward in the chair confirmation of the Galactose. Show
Key Areas Covered1. What is Glucose Key Terms: Aldohexose, Carbohydrates, D-Glucose, Galactose, Glucose, Hexose, Molecular Formula, Monosaccharides  What is GlucoseGlucose is a simple sugar. It is a monosaccharide. The molecular formula of Glucose is C6H12O6. Its chemical structure has four –OH groups along with a -CH2OH group. Since it has six –OH groups, glucose is called a Hexose. In the Fischer projection, glucose has a terminal aldehyde group. Therefore, glucose is called an aldohexose. Figure 1: The chair confirmation of D-Glucose The above image shows the general structure of glucose. This image indicates that glucose has four chiral centers. (A chiral center is a carbon atom having four different groups attached to it.) Therefore, glucose has stereoisomers. The naturally occurring glucose is known as D-Glucose. The isomer of D-Glucose is L-Glucose. But the L-Glucose does not occur naturally. Glucose is water soluble and is colorless when dissolved in water. Glucose can occur as an open chain or as a cyclic structure. But the open chain is typically unstable and spontaneously converts into cyclic form. The melting point of glucose is about 1460C (for alpha-D-Glucose). Aqueous solutions of glucose are able to rotate plane polarized light. D-Glucose rotates light clockwise and L-Glucose rotates light anticlockwise. Glucose act as a monomer for the formation of a number of important polysaccharides. Some polymers that have glucose as the monomer include starch, cellulose, and glycogen. What is GalactoseGalactose is a simple sugar and a monosaccharide. The molecular formula of galactose is also C6H12O6. Its chemical structure has four –OH groups along with a -CH2OH group. Same as glucose, galactose is also an aldohexose due to the presence of six carbon atoms and a terminal aldehyde group. Figure 2: Fischer Projection of D-Galactose Galactose can exist either in the open chain form or the cyclic form. Galactose contributes to the formation of some disaccharides such as Lactose (Glucose + Galactose) and Galactan (composed of Galactose). The melting point of galactose is about 1670C. Galactose is also soluble in water, but the solubility is less than that of glucose. Similarities Between Glucose and Galactose
Difference Between Glucose and GalactoseDefinitionGlucose:Glucose is a simple sugar composed of C, H, and O atoms and tastes sweet. Galactose: Galactose is a simple sugar composed of C, H, and O atoms and is less sweeter than glucose. Position of –OH GroupThe main difference between glucose and galactose is the chemical structure; the position of each –OH group present in both molecules. This difference occurs in the 4th carbon atom. The following image shows this in detail. Figure 3: Glucose vs. Galactose Glucose:The –OH group of the 4th carbon (from the top) of D-Glucose is directed towards right side. Galactose: The –OH group of the 4th carbon of D-Galactose is directed towards the left side. StabilityGlucose: Glucose is more stable. Galactose:Galactose is less stable. SweetnessGlucose:Glucose is sweeter. Galactose: Galactose is less sweeter than Glucose. Melting PointGlucose:The melting point of glucose is about 146-150oC. Galactose:The melting point of galactose is about 167oC. ConclusionGlucose and Galactose are very important simple sugars as monosaccharides as well as polysaccharides, which are formed after their polymerization. The chemical formula and the molar mass of both molecules are the same, but the difference between glucose and galactose lies in the arrangement of –OH groups along the carbon chain. References:1. Steane, Richard. “Molecular structure of glucose and other carbohydrates.” Structure of glucose and other carbohydrate molecules. N.p., n.d. Web. Available here. 29 June 2017. Image Courtesy:1.”Beta-D-Glucose” By Yikrazuul – Own work (Public Domain) via Commons Wikimedia How are glucose, galactose and fructose different?Glucose and galactose are stereoisomers (have atoms bonded together in the same order, but differently arranged in space). They differ in their stereochemistry at carbon 4. Fructose is a structural isomer of glucose and galactose (has the same atoms, but bonded together in a different order).
What is a common property of glucose, galactose and fructose?Glucose, galactose, and fructose are carbohydrates, and monosaccharides in particular. The isomers glucose, glactose, and fructose all have the same chemical formula, C6H12O2 .
Do glucose and fructose have the same properties?Glucose and fructose are functional isomers of each other because they have same molecular formula that is C6H12O6 But different functional group in their chemical formula. Glucose has aldehyde group while fructose has ketone as functional group. They differ in the nature of the functional group.
What is a common property of glucose, galactose and fructose quizlet?Terms in this set (3) The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6) but different structural formulas, as represented in the figure.
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