Difference Between Aldose And Ketose

The Basic Difference Between Aldose And Ketose is that Aldose contains only one aldehyde group in a single molecule and tends to isomerism into ketoses while ketos contain one ketos group in one molecule rather than aldehyde and change isomerism into aldoses if the carbonyl group is present at the end of the chain.

In this post, you are going to learn about Aldose vs. Ketose step by step with Diagram.

This post includes:

  • An overview
  • What is Aldose?
  • What is ketose?
  • Differences
  • Lots more

So if you want to get benefits from this post you’ll love this post.

Let’s Dive right in…!

An Overview

Ketose and aldose both belong to the monosaccharides and can be differentiated on the basis of the group they are consist of. aldose contains an aldehyde group while Ketose consists of a ketone group. An aldose is such a type of monosaccharide whose carbon skeleton consists of an aldehyde group while ketose is such a type of monosaccharide whose carbon skeleton consists of a ketone group.

aldose is commonly found in plants and ketones are present in reducing sugar where they isomerize to aldose. a large quantity is used in processed food. ribulose, fructose are common examples of ketose.

by performing an experiment named Seliwanoff’s Test we can easily distinguish between aldose and ketose. if the color changes to light pink it is said to be aldose whereas if the color turns into deep cherry red it is said to be ketones.

Difference Between Aldose And Ketose in tabular form 



Consists of one aldehyde group in a single molecule.

Consist of one ketone group in a single molecule.


It is a monosaccharide containing the aldehyde also contains a carbon chain in the structure. 

the ketose is also considered a monosaccharide that contains a ketone group instead of an aldehyde with a carbon chain. 

Shows a light pink color in Seliwanoff’s Test and reacts slowly.

Shows deep cherry red color in Seliwanoff’s Test and reacts very fast with resorcinol.


glyceraldehyde, Glycolaldehyde, and erythrose are common examples of Aldose. 

Fructose, xylulose, tagatose, ribulose, erythrulose,  and sorbose are common examples of Ketose.

Tends to isomerize into ketoses.

Tends to isomerize into aldose by having a carbonyl group at the end of the chain.

Consists of a carbon atom that is bonded to a hydrogen atom and double-bonded to an oxygen atom.

It is a carbonyl group linked with two other carbon atoms.

Aldose group diagram

ketose group diagram

What is Aldose?

Since Aldose is a monosaccharide having an aldehyde group at the end of its structural chain. Cn (H2O)n is known as the formula for Aldose. the aldehyde functional group represents the carbon atom with a double bond to the oxygen atom.  

the simple form of aldose is known as glycolaldehyde diose having two carbon atoms bonded tightly together with the aldehyde group. the carbohydrates of sugar belonging to this group play a vital role in numerous functions in living things. the Aldose can be distinguished easily from that of Ketose by doing the Seliwanoff test.  they show a slow reaction rate by leaving pink light color. 

Examples of Aldose

some examples of Aldose containing aldehyde group are as follows:

  • arabinose
  • glyceraldehyde
  • glucose
  • xylose
  • mannose
  • allose
  • Glycolaldehyde
  • erythrose
  • ribose
  •  altrose
  • gulose
  • talose
  • galactose

What is ketose?

like Aldose, Ketose also a monosaccharide that includes carbohydrate molecules of the ketone group with a structural carbon chain. dihydroxyacetone is a common example of ketose that have three carbon atom in its structure.

the three-carbon structures can be divided into two hydroxyl groups and a keto group. They react easily with crystalline compounds like resorcinol by producing dark reddish colors. RCOR has considered the formula for ketose having a carbonyl group (CO) and R group. 

Examples of ketose

some examples of Ketose containing ketone group are as follows:

  • Tagatose
  • Erythrulose
  • Psychos
  • Ribulose
  • Sorbose
  • Fructose
  • Xylulose

Key Differences

  1. the Aldose and Ketose both are monosaccharides containing aldehyde and ketone groups simultaneously along with carbon chain in their structures.
  2. by conducting the Seliwanoff test, we can distinguish both from each other as the aldose produces a light pink color by reacting slowly while the ketose leaves dark reddish color by reacting with crystalline compounds of resorcinol.
  3. by reducing the sugar work as a reducing agent in ketones and aldehydes to make them free group. this phenomenon is known as isomerism into aldose by adding the carbonyl group in their last molecule.
  4. the aldose group will possibly form glycolaldehyde having one carbon atom while the ketone formation turns into dihydroxyacetone.
  5. Examples of aldose include glycolaldehyde, glyceraldehyde, erythrose, ribose, arabinose, xylose, allose, altrose, glucose, mannose, gulose, talose, and galactose.
  6. Fructose, ribulose, and xylulose are the three important examples of ketosis sugars. Other examples include erythrulose, tagatose, sorbose, psychosis, and dihydroxyacetone, even assuming the latter is not classified as ketosis.
  7. the Aldose can change into Ketose by decomposing it by the process of isomerization. same way, the ketose can also be changed into aldehydes by decomposing or separating the carbonyl group present at the end of every atom. 
  8. In Seliwanoff’s check, the aldoses generally tend to respond to a common tempo and have a slightly pinkish hue, however, the ketoses meet with resorcinol to create a dark pinkish hue.

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