Define monosaccharide disaccharide and polysaccharide give at least two examples of each. which of these is the

Saccharides are carbohydrates, molecules containing Carbon (C), Hydrogen (H), and Oxygen (O). "Saccharo" means sugar in Greek. Also Greek, "mono" means one, "di" means two, and "poly" means many.
A sugar molecule is based upon a ring of carbons with H's and OH's attached. One sugar molecule alone is a monosacchararide, like glucose and fructose. Two sugar molecules bonded together covalently is a disaccharide, like lactose (milk sugar) and sucrose (table sugar). Many sugar molecules (upwards of hundreds or thousands) bonded together covalently is a polysaccharide. Examples are glycogen (animal starch) and cellulose (plant starch).

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).