Which of the following is not a chemically modified sugar ?

Options

A. Glucosamine
B. N acetyl galactosamine
C. Galacturonic acid
D. Dihydroxy acetone

Answer

To determine which of the following options is not a chemically modified sugar, we need to analyze each of the given options:

1. **Glucosamine**:
- Glucosamine is an amino sugar derived from glucose. It is formed by the substitution of an amino group (-NH2) for a hydroxyl group (-OH) in glucose. Therefore, glucosamine is a chemically modified sugar.

2. **N-acetylglucosamine**:
- N-acetylglucosamine is another amino sugar, which is a derivative of glucosamine where an acetyl group (-COCH3) replaces the amino group. This modification also classifies it as a chemically modified sugar.

3. **Galacturonic acid**:
- Galacturonic acid is produced by the oxidation of galactose, which transforms the hydroxyl group of galactose into a carboxylic acid group. This makes galacturonic acid a chemically modified sugar as well.

4. **Dihydroxyacetone**:
- Dihydroxyacetone is a simple carbohydrate (saccharide) that consists of three carbon atoms. It is not modified chemically from a more complex sugar; instead, it is a basic sugar itself. Therefore, it is not classified as a chemically modified sugar.

Based on the analysis, the option that is not a chemically modified sugar is:

**Dihydroxyacetone**.

### Summary of the Steps:
1. Identify and analyze each option.
2. Determine if the sugar is chemically modified or not.
3. Conclude that dihydroxyacetone is the only option that is not a chemically modified sugar.