This monosaccharide is the 2 epimer of glucose.

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Multiple Choice

This monosaccharide is the 2 epimer of glucose.

Explanation:
Epimers are stereoisomers that differ at exactly one chiral center. For aldoses like glucose, the carbon next to the carbonyl (C-2) is the first stereocenter, so the 2-epimer means flipping the configuration at C-2. In the common representation of D-glucose, the OH on C-2 points to the right. Inverting that center gives the structure with the OH on C-2 to the left, which corresponds to D-mannose. So the monosaccharide that is the 2-epimer of glucose is mannose. Galactose, by contrast, differs from glucose at C-4, not C-2, so it’s the 4-epimer. Fructose is a ketose, not an aldose, so it isn’t an epimer of glucose. Sucrose is a disaccharide composed of glucose and fructose, not a monosaccharide, so it isn’t an epimer of glucose either.

Epimers are stereoisomers that differ at exactly one chiral center. For aldoses like glucose, the carbon next to the carbonyl (C-2) is the first stereocenter, so the 2-epimer means flipping the configuration at C-2.

In the common representation of D-glucose, the OH on C-2 points to the right. Inverting that center gives the structure with the OH on C-2 to the left, which corresponds to D-mannose. So the monosaccharide that is the 2-epimer of glucose is mannose.

Galactose, by contrast, differs from glucose at C-4, not C-2, so it’s the 4-epimer. Fructose is a ketose, not an aldose, so it isn’t an epimer of glucose. Sucrose is a disaccharide composed of glucose and fructose, not a monosaccharide, so it isn’t an epimer of glucose either.

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