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biochemistry question

Doing some work on glucose and as we know its a reducing sugar
after some research, it seems that a sugar can only be reducing if it has an aldehyde group as part of its straight chain structure. Is this correct?

essentially, my question is, how does the ringed structure of glucose become the straight chained structure. Is that oxidation? Or is oxidation the stage when the aldehyde group is converted to something else? And what would it be converted to? A carboxyl or carboxylate group?
for example, what happens to glucose, structurally, when it reduces something like Tollen's Reagent?

A lot of questions I know, but if someone could clear it up I would appreciate it.
Thanks in advance
plasmaman
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Kemmist
3
Yes, the aldehyde group in the chain from acts as the reducing 'agent'. The Silver ions in Tollens reagents are reduced to Silver metal (gain in electrons from Ag+ to Ag).
The aldehyde itself gets oxidised to the carboxylic acid. If the solution is basic then it will be the deprotonated carboxylate form that is present.

Nice summary here

http://en.wikipedia.org/wiki/Reducing_sugar

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