Question

Name which, if any, of the following groups are not aldose-ketose pairs: D-ribose and D-ribulose, D-glucose and Dfructose, nglyceraldehyde and dihydroxyacetone.

Short answer

All listed pairs are aldose-ketose pairs.

Step-by-step solution

- Understand Aldoses and Ketoses

Aldoses are sugars with an aldehyde group (-CHO) at the end of the molecule, while ketoses have a ketone group (C=O) usually at the second carbon atom.

- Identify Functional Groups in Each Sugar

Identify whether each sugar listed has an aldehyde group (making it an aldose) or a ketone group (making it a ketose).

- Analyze Each Pair

Compare the two sugars in each pair to see if one is an aldose and the other is a ketose.

- Check D-ribose and D-ribulose

D-ribose is an aldose because it has an aldehyde group. D-ribulose is a ketose because it has a ketone group. Therefore, D-ribose and D-ribulose form an aldose-ketose pair.

- Check D-glucose and D-fructose

D-glucose is an aldose because it has an aldehyde group. D-fructose is a ketose because it has a ketone group. Therefore, D-glucose and D-fructose form an aldose-ketose pair.

- Check Glyceraldehyde and Dihydroxyacetone

Glyceraldehyde is an aldose because it has an aldehyde group. Dihydroxyacetone is a ketose because it has a ketone group. Therefore, glyceraldehyde and dihydroxyacetone form an aldose-ketose pair.

- Result

Since all the given pairs (D-ribose and D-ribulose, D-glucose and D-fructose, glyceraldehyde and dihydroxyacetone) are aldose-ketose pairs, none of them are non-aldose-ketose pairs.

Key concepts

aldose

An aldose is a type of sugar that contains an aldehyde group (-CHO) at the end of its carbon chain.
This aldehyde group is attached to the first carbon atom.
Because of this structure, aldoses are also known as 'aldose sugars'.
Some common examples of aldoses are D-glucose, D-ribose, and glyceraldehyde.
In aldose sugars, the presence of the aldehyde group makes them highly reactive.

ketose

Ketose sugars contain a ketone group (C=O) typically at the second carbon atom of the molecule.
This gives them different reactivity and properties than aldoses.
Some well-known examples of ketoses include D-fructose, D-ribulose, and dihydroxyacetone.
The ketone group in ketoses is very important for their biochemical properties and reactions.

functional groups in sugars

Functional groups are specific groups of atoms within molecules that determine the chemical properties of those molecules.
In sugars, the two most important functional groups are the aldehyde group (-CHO) in aldoses and the ketone group (C=O) in ketoses.
The presence of these functional groups categorizes sugars and greatly influences how they behave in chemical reactions.

D-ribose

D-ribose is a simple sugar and an aldose because it contains an aldehyde group.
It's a five-carbon sugar, also known as a pentose.
D-ribose plays a critical role in biology as a component of RNA (ribonucleic acid), which is crucial for genetic information and protein synthesis.
It's essential for energy production and is a fundamental part of our metabolic processes.

D-ribulose

D-ribulose is a ketose sugar with a ketone group located at the second carbon atom. Unlike D-ribose, which is an aldose, D-ribulose plays a significant role in the pentose phosphate pathway, which is important for metabolism in cells. D-ribulose is also involved in the Calvin cycle, which plants use for photosynthesis.

D-glucose

D-glucose is one of the most important and commonly known aldoses.
It has six carbon atoms, making it a hexose.
You might know it as 'blood sugar' because it's a primary energy source for cells in the human body.
D-glucose is an essential part of many biological processes, including cellular respiration where it is broken down to produce energy in the form of ATP.

D-fructose

D-fructose is a common ketose sugar found naturally in many fruits and honey.
It has six carbon atoms, just like D-glucose, making it a hexose sugar.
Because of its sweet taste, it's often referred to as fruit sugar.
D-fructose is used frequently in food processing and can be metabolized by the body to produce energy.

glyceraldehyde

Glyceraldehyde is a simple three-carbon aldose known as a triose.
It contains an aldehyde group at the end of its molecule.
Glyceraldehyde is an important intermediate in various metabolic pathways, including glycolysis.
Along with dihydroxyacetone, it plays a critical role in the breakdown and utilization of glucose within cells.

dihydroxyacetone

Dihydroxyacetone is a ketose with three carbon atoms, making it a triose.
It contains a ketone group and is a fundamental intermediate in metabolic pathways such as gluconeogenesis and glycolysis.
Dihydroxyacetone is also used in the cosmetic industry as a skin-darkening agent in sunless tanning products.