What are reducing and non-reducing sugars ? What is the structural feature characterising reducing sugars ? What is an invert sugar ?

Explanation

Sugars which can reduce Tollen.s reagent or Fehling.s solution are called reducing sugars. The sugars which donot reduce Tollen.s reagent or Fehling solution are called non-reducing sugars.
The characteristic structural feature of reducing sugars is the presence of either `alpha`-hydroxy aldehydic group, `(-underset(OH)underset(|)CH-CHO)` such as glucose, mannose, galactose, etc., or a-hydroxy keto group `(-CO-CH_(2)OH)` as present in fructose.