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Difference between reducing and non-reducing sugars?

I'm on the WJEC board and although the specification doesn't mention you have to know the difference, the boards revision guide reads

"Make sure you know the difference between a reducing and a non-reducing sugar and the appropriate food test"

So, I'm going to learn it, just in case. Only, we, went through the test in class, and we were never told the actual difference, only the tests for the different ones and the results, and the revision guide tells nothing. I've googled it but the answers seem far too indepth and not tailored for as level. And every page is mentioning terminaolgy I have never come across.

Can anyone shed some light on this?
Reducing sugars turn Benedicts from Bluey/Green to a Brick red precipitate when heated

Non reducing don't

Since it's a REDUCING SUGAR, i think the reducing sugar itself becomes oxidised and reduces the Benedicts to make it go red due to the oxygen group being/not being in a certain place, i can't remember
just if you really wanna know why this works is that the monosaccharides you come across in this part of the course can be either aldoses (containing a aldehyde functional group) or ketoses (containing a ketone functional group) if you do chemistry you will know that ketones cant be oxidized but aldehydes can :smile:
Benedict test

* Test to confirm reducing properties of sugars.
* Add a few drops of benedict solution into the sugar and boil. If it shows a brickred precipitate, a reducing sugar is present. Since copper 2+ is reduced in copper +1 which shows are brick red precipitate


Taken off Wiki, but since i was reading it and need to learn about it and so do you, i thought id make life easier by copying it here aswell!
Reply 4
Avatar for digitalis
digitalis
17
Reducing sugars cause other compounds to be reduced eg Cu2+ to Cu, with the sugar in turn being oxidised. Non reducing sugars don't display this characteristic.
Reducing:

Blue Cu2+ ------> Red Cu+

So, the reducing centre in the sugar is reduced (i.e. gains an electron) by the Benedicts solution (CuSO4).

Non Reducing:

Does not get reduced, so you need to boil it in acid, THEN re-do the test and it should turn re, like a reducing sugatr.
Reply 6
Avatar for Wangers
Wangers
16
Speedbird2007
Reducing:

Blue Cu2+ ------> Red Cu+

So, the reducing centre in the sugar is reduced (i.e. gains an electron) by the Benedicts solution (CuSO4).

Non Reducing:

Does not get reduced, so you need to boil it in acid, THEN re-do the test and it should turn re, like a reducing sugatr.


Nearly, heat with acid is usually sufficent, then nutralise with Alkaline , then run Benedicts. This won't necessarily bugger up an experiement, but it will cost you marks.
Cheers Wangers. I haven't seen it in any mark schemes or my textbook or module book, but if you say so...
Reply 8
Avatar for ajdj
ajdj
reducing sugars are monosachharides and sometimes disaccharides while non-reducing sugars are always disaccharides. so when u boil it with an acid u brake the bonds and form shorter monosaccharides.

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