which is not true about monosaccharides?

Options

A. reducing nature
B. soluble in water
C. sweet in taste
D. always ketose

Answer

To determine which statement is not true about monosaccharides, let's analyze each option step by step:

### Step 1: Understanding Monosaccharides
Monosaccharides are the simplest form of carbohydrates. They are the basic building blocks of more complex carbohydrates and cannot be hydrolyzed into simpler sugars.

### Step 2: Evaluating Each Option
1. **Reducing Nature**: Monosaccharides are known to have reducing properties because they contain free aldehyde or ketone groups. This means they can act as reducing agents. Therefore, this statement is true.

2. **Soluble in Water**: Monosaccharides are generally soluble in water due to their hydroxyl (-OH) groups, which can form hydrogen bonds with water molecules. Thus, this statement is also true.

3. **Sweet in Taste**: Many monosaccharides, such as glucose and fructose, are sweet in taste. This characteristic is true for most monosaccharides.

4. **Always Keto**: This statement is not true. Monosaccharides can be classified as either aldoses (which contain an aldehyde group) or ketoses (which contain a ketone group). For example, glucose is an aldose, while fructose is a ketose. Therefore, saying that monosaccharides are always keto is incorrect.

### Conclusion
The statement that is not true about monosaccharides is: **"Always keto."**

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