Question

The two functional groups characteristic of sugars are

• A. hydroxyl and methyl
• B. carbonyl and phosphate
• C. carbonyl and methyl
• D. carbonyl and hydroxyl

Answer 1

The Correct Option is D

The question asks about the functional groups that are characteristic of sugars. Understanding the basic chemistry of sugars is crucial to address this question.

Sugars, also known as saccharides, are essential biomolecules that primarily consist of the elements carbon, hydrogen, and oxygen. The structural properties of these molecules are largely determined by the presence of specific functional groups. In sugars, two functional groups are particularly prominent:

1. Hydroxyl Group (-OH): Sugars feature multiple hydroxyl groups. These are responsible for the solubility of sugars in water, as the hydroxyl groups can form hydrogen bonds with water molecules. This solubility is critical for their biological roles in metabolic pathways.
2. Carbonyl Group (C=O): This group is present as an aldehyde group at the end of the molecule (in aldoses like glucose) or as a ketone group in the middle (in ketoses like fructose). The carbonyl group's presence is key to the sugar's ability to act as a reducing sugar, participating in certain biochemical reactions.

The correct combination of functional groups characteristic of sugars includes both the carbonyl and hydroxyl groups. Based on this information:

1. The option "hydroxyl and methyl" is incorrect because sugars typically do not contain methyl groups as a defining characteristic.
2. "Carbonyl and phosphate" is also incorrect. Phosphate groups are not characteristic of simple sugars but are more relevant in nucleotides and energy carriers like ATP.
3. "Carbonyl and methyl" is incorrect because sugars do not conventionally feature methyl groups as a primary functional group.
4. The correct option, "carbonyl and hydroxyl," accurately identifies the functional groups that define sugars.

Thus, the correct answer to the question is carbonyl and hydroxyl.