What are carbohydrates? Classify them by their behaviour on hydrolysis, with two examples of each class.

How to lay out the answer. Follow the frame, then write it in your own words.

1 · Define. Optically active polyhydroxy aldehydes or ketones, or compounds that give such units on hydrolysis.
2 · Monosaccharides. Cannot be hydrolysed further: glucose, fructose.
3 · Oligosaccharides. Give 2 to 10 units on hydrolysis: sucrose, maltose (disaccharides).
4 · Polysaccharides. Give a large number of units: starch, cellulose.
5 · Add reducing and non-reducing. Reducing sugars reduce Fehling's and Tollens' reagents (glucose, maltose); sucrose is non-reducing.
6 · Close in one line. So the number of units released on hydrolysis decides the class.

Scoring tip: Give two examples for every class. A class without an example often loses half its mark.