Question

Which of the following is the smallest is the carbohydrate - triose?

• A. Ribose
• B. Glucose
• C. Glyceraldehyde
• D. Dihydroxyacetone

Hint:

Glyceraldehyde is the reference sugar for the D/L naming system. If the -OH on the chiral carbon furthest from the carbonyl group is on the right, it is D-glyceraldehyde.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Monosaccharides are classified based on the number of carbon atoms they contain. A "triose" is a monosaccharide containing exactly three carbon atoms. These are the simplest possible sugars. They serve as essential intermediates in metabolic pathways like glycolysis and the Calvin cycle.

Step 2: Detailed Explanation:
The chemical formula for a triose is \(C_3H_6O_3\). There are only two trioses: glyceraldehyde (an aldotriose) and dihydroxyacetone (a ketotriose). Glyceraldehyde is often considered the "smallest" or "simplest" carbohydrate because it contains a chiral center (in its D and L forms) and is the building block for larger aldose sugars.
Let's evaluate the options:
- Ribose (Option 1) is a pentose (\(C_5H_{10}O_5\)).
- Glucose (Option 2) is a hexose (\(C_6H_{12}O_6\)).
- Glyceraldehyde (Option 3) is a 3-carbon sugar and is the smallest aldose.
- Dihydroxyacetone (Option 4) is also a 3-carbon sugar (ketose).
Between the two trioses, glyceraldehyde is historically and structurally the reference molecule for carbohydrate stereochemistry. In many contexts, "smallest carbohydrate" refers to the simplest aldose, which is glyceraldehyde. It is the first sugar produced in the Calvin cycle (as G3P).

Step 3: Final Answer:
Glyceraldehyde is the simplest aldotriose and the smallest functional unit of the carbohydrate hierarchy.