Help me define: Reducing sugars and non-reducing sugars?

Question

Needed for my homework and I havn't got a clue...

Answer 1

A reducing sugar is a type of sugar with an aldehyde group. This allows the sugar to act as a reducing agent, for example in the Maillard reaction and Benedict's reaction. Reducing sugars include fructose, glucose, glyceraldehyde, lactose, arabinose and maltose. All monosaccharides which contain ketone groups are known as ketoses, and those which contain aldehyde groups are known as aldoses. Significantly, sucrose is not a reducing sugar. It is infact known as a non-reducing sugar.
Benedict's reagent is used to determine if a reducing sugar is present. If it is a reducing sugar, the mixture will turn green/orange/red. Fehling's solution can also be used for the same purpose, as both contain copper (II) ions which are reduced to a brick red precipitate of copper (I) oxide when the solution is heated.
A reducing sugar occurs when its anomeric carbon is free, which is the chiral carbon. Since sugars occur in a chain as well as a ring structure, it is possible to have an equilibrium between these two forms. When the hemi-acetal or ketal hydroxylgroup is free, it is not locked, not linked to another (sugar)molecule, the aldehyde (or keto-) form (i.e. the chain-form) is available for reducing copper (II) ions. When a sugar is oxidized it is likely to form a carbic acid.

The classical definition of Reducing Sugars is "Reducing substances in
cane and its products interpreted as invert sugar". Many sugar refineries
refer to reducing sugars as invert (glucose & fructose).
There are several official ICUMSA methods for the determination of
reducing sugars. The Lane-Eynon method is generally recommended for the
sugar industry. It is this method where the name reducing sugars is
derived from.
In the Lane Eynon method the test sample (containing sucrose & invert
sugar) is added volumetricly to a defined volume of a strongly alkaline
cupric-complex salt solution, called Fehling's solution, which is then
reacted by boiling. The remainder of the test solution is then added,
until, at the end-point, the cupric ions are completely REDUCED to cuprous
oxide and a blue color of the solution will disappear. The sharpness of
the end-point is improved by the use of an indicator, methylene blue,
which is decolorized in the presence of a minute excess of reducing sugars.
Sucrose will not reduce the cupric ions therefore they are refered to as
non reducing.


Reducing Sugars (Benedict's test). All monosaccharides and most disaccharides (except sucrose) will reduce copper (II) sulphate, producing a precipitate of copper (I) oxide on heating, so they are called reducing sugars. Benedict’s reagent is an aqueous solution of copper (II) sulphate, sodium carbonate and sodium citrate. To approximately 2 cm³ of test solution add an equal quantity of Benedict’s reagent. Shake, and heat for a few minutes at 95°C in a water bath. A precipitate indicates reducing sugar. The colour and density of the precipitate gives an indication of the amount of reducing sugar present, so this test is semi-quantitative. The original pale blue colour means no reducing sugar, a green precipitate means relatively little sugar; a brown or red precipitate means progressively more sugar is present.
Non-reducing Sugars (Benedict's test). Sucrose is called a non-reducing sugar because it does not reduce copper sulphate, so there is no direct test for sucrose. However, if it is first hydrolysed (broken down) to its constituent monosaccharides (glucose and fructose), it will then give a positive Benedict's test. So sucrose is the only sugar that will give a negative Benedict's test before hydrolysis and a positive test afterwards. First test a sample for reducing sugars, to see if there are any present bef7ore hydrolysis. Then, using a separate sample, boil the test solution with dilute hydrochloric acid for a few minutes to hydrolyse the glycosidic bond. Neutralise the solution by gently adding small amounts of solid sodium hydrogen carbonate until it stops fizzing, then test as before for reducing sugars.

Answer 2

Define Reduce

Answer 3

Invert Sugar Definition

Answer 4

Any sugars that provides electrons to carry out reduction is called reducing sugars. For example Benedict's Solution Copper II Sulphate. The Cu2+ ions from copper sulphate are reduced by electrons from -C=O group found in sugars to form Cu+ ions.
And non-reducing sugars is completely opposite to Reducing sugars. I hopw this will help you.