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Aldose vs. Ketose — What's the Difference?

By Tayyaba Rehman — Updated on September 20, 2023
An aldose is a monosaccharide with an aldehyde group, while a ketose is a monosaccharide with a ketone group.
Aldose vs. Ketose — What's the Difference?

Difference Between Aldose and Ketose


Key Differences

Aldose is a type of monosaccharide (simple sugar) that contains an aldehyde group (-CHO) as its primary functional group. On the other hand, Ketose is a monosaccharide containing a ketone group (C=O) as its primary functional group.
In Aldose sugars, the carbonyl group is at the end of the carbon chain, forming an aldehyde. In contrast, in Ketose sugars, the carbonyl group is found within the carbon chain, forming a ketone.
As a result of their structural differences, Aldose and Ketose sugars may have different properties and reactivities. For example, aldoses can easily be oxidized to form aldonic acids, while ketoses do not directly form similar acids.
Common examples of Aldose sugars include glucose and galactose. Common examples of Ketose sugars include fructose.
Both Aldose and Ketose are fundamental to biochemistry and play essential roles in metabolism. However, they can be isomerized into each other through certain chemical reactions.

Comparison Chart

Functional Group

Contains an aldehyde group (-CHO).
Contains a ketone group (C=O).

Position of Group

At the end of the carbon chain.
Within the carbon chain.


Glucose, Galactose.

Oxidation Products

Can form aldonic acids upon oxidation.
Doesn't directly form similar acids.

Biochemical Role

Used in glycolysis and energy production.
Converted to glucose in the liver for energy.

Compare with Definitions


Aldehyde Sugar: A sugar containing an aldehyde group.
Glucose is a common aldose found in many foods.


Structural Feature: Contains the carbonyl group within its carbon chain.
The positioning of the ketone group in a ketose makes it distinct.


Structural Aspect: Contains the carbonyl group at the carbon chain's end.
The aldehyde group in an aldose gives it unique properties.


Different Reactivity: Not directly oxidized to acids like aldoses.
Ketose sugars have different chemical reactions compared to aldoses.


Biochemical Role: Participates in various metabolic pathways.
Aldose sugars like glucose are crucial in glycolysis.


Distinct Monosaccharide: Another fundamental type of simple sugar.
Ketose sugars can be isomerized to aldose sugars under specific conditions.


Monosaccharide Type: One of the basic types of simple sugars.
An aldose can play a fundamental role in energy production.


Ketone Sugar: A sugar containing a ketone group.
Fructose, found in many fruits, is a ketose.


Reactive Sugar: Can easily be oxidized.
When oxidized, an aldose can form aldonic acid.


Metabolic Pathway: Converted to glucose in the liver.
Even though fructose is a ketose, the body processes it differently than glucose.


An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms. Aldoses can be distinguished from ketoses, which have the carbonyl group away from the end of the molecule, and are therefore ketones.


A ketose is a monosaccharide containing one ketone group per molecule. The simplest ketose is dihydroxyacetone, which has only three carbon atoms, and it is the only one with no optical activity.


Any of a class of monosaccharide sugars containing an aldehyde group.


Any of various carbohydrates containing a ketone group.


Any of a class of monosaccharides having an aldehyde or hemiacetal functional group.


(carbohydrate) A saccharide containing a ketone functional group.


A monosaccharide sugar that contains the aldehyde group or is hemiacetal


Any monosaccharide sugar that contains a ketone group or its hemiacetal

Common Curiosities

Can aldose and ketose sugars interconvert?

Yes, they can be isomerized into each other under certain conditions.

Do aldoses and ketoses play roles in human health issues?

Yes, excessive consumption, especially of processed sugars, can lead to health issues like diabetes.

Are all aldoses and ketoses sweet-tasting?

Not necessarily. While many are sweet, the sweetness can vary, and not all are perceived as sweet by human taste buds.

Is fructose, a ketose, less reactive than glucose, an aldose?

In terms of oxidation to form acids, yes. Fructose doesn't directly form similar acids like glucose.

Are both aldoses and ketoses found in nature?

Yes, both are naturally occurring sugars found in various sources.

Can both aldoses and ketoses be used for energy?

Yes, both types of sugars can be metabolized for energy.

Are the terms aldose and ketose only related to sugars?

Primarily, yes. They refer to the type of functional group present in certain monosaccharides.

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Author Spotlight

Written by
Tayyaba Rehman
Tayyaba Rehman is a distinguished writer, currently serving as a primary contributor to As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.

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