biology question

A reducing sugar is a type of sugar with an aldehyde or ketone group. This allows the sugar to act as a reducing agent, for example in the Maillard reaction and Benedict's reaction. Reducing sugars include 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 in fact 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. 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 its carbonyl group (i.e. aldehyde or ketone group) is converted to a carboxyl group.

What is reducing sugar and why is it called reducing?
-some sugar have carbonyl groups (C=O) which can be oxidised to carboxylic acids(COOH), REDUCING other chemicals in the process.
e.g. reducing sugar+Cu2+(component of Benedict's solution)-->oxidised sugar+Cu+

What is aldehyde醛(-CHO) & ketone酮(-CO)?
Aldehyde & ketone are funtional groups of organic compounds.

Monosaccharide單糖 contains an aldehyde group is called aldose醛糖.
Monosaccharide單糖 contains a ketone group a ketose酮糖.

我諗發問姐應該係f.4 or f.5既學生....
or evenf.3啦,,,,aldehyde & ketone應該唔識住既,,,
如果係f.3-5既學生,,,,,,
你其實只需要知道sugar分reducing sugar同non-reducing sugar,,
大部分既sugar都係reducing sugar,,,
係f.3-f.5既syllabus入面,,,,,
應該只有sucrose係non-reduing sugar,,,
reducing sugar可以用Benedict"s test去test佢,,
會有+ve result,,即係有brick red precipitate,,,
但sucrose就唔會有任何visible change,,,,
至於ketone同aldehyde就係一d organic既groups,,,
即係會有個 (-HO) group attach左係尾或者中間,,,,
要到f.6-7既chem先會學,,bio都好似會學,,,(本人f.6-7冇讀bio,,,所以唔係好知)
至於點test sucrose,,,f.6-7會學,,,,
sucrose去到攝氏186度會melt,,,變做caramel,,,,
then再test佢個melting point就知佢係呼sucrose,,,
希望解得你明!!!