Why is ribose a stronger reducing sugar than glucose?

[ashih]

Hi all, I would like to understand what makes ribose a stronger reducing sugar than glucose. They both have an aldehyde functional group to be oxidized but they differ in their structure as a pentose vs hexose. Is it their structure that makes one more easily converted to an open structure and be oxidized than the other? Any clue or direction will help a lot! Thanks

[Elite Engineer]

I think it has to do with their conformational structures. Glucose having the ability to change into a boat conformation renders it theoretically more stable than ribose, which utilizes the envelope or twist conformation as it's most stable conformation.

 

-since ribose has a generally less stable conformation than glucose, it should be more reactive.

 

~ee

[Carvone]

What makes you think ribose is a stronger reducing agent than glucose?

 

I am just curious, since in the 2,2'-bicinchoninic acid reducing end analysis, glucose gives a much higher response curve than ribose (Absorbance/concentration Slope). I recognize the only factor is not the reactivity to the 2,2'-bicinchoninate disodium salt at the reducing end but also the absorptivity of the new compound produced from the sugar and the 2,2'-bicinchoninate disodium salt that gives the blue color at 560 nm ABS. See std curve below.

 

One possibility is since Ribose is a 5 carbon ring (aldopentose) while glucose is a 6 carbon ring (aldohexose), there is more pressure for ribose to open up (since ring bonds will be tighter stretched) thus making it more reactive at the reducing end.