CARBOHYDRATES

Simple classification

Carbohydrates store energy and provide building materials.

Relative sweetness of sugars(sucrose = 1.00)

Monosaccharides

• Monosaccharides are often used as building blocks of large molecules.

• Ribose and deoxyribose are components of nucleic acid. • Glucose is component of large energy storage molecules.

Disaccharides

Disaccharides are composed of two monosaccharides linked by a covalent bond.

Storage Polysaccharides

Plant cells store glucose in form of starch (amylose and amylopectin).

Animal cells store glucose in form ofglycogen, which is more extensivelybranched and contains longer chainsthan amylose and amylopectin.

Structural polysaccharides

Cellulose

Starch consists of α-glucose subunits while cellulose consists of β-glucose subunits.

Cellulose fibre from a pine tree(20X magnification).

Cellulose fibre can be very strong and are quite resistant to metabolic breakdown, which is one reason why wood is such a good building materials.

Chitin

Chitin can be considered as modified formof cellulose and is the principal structuralelement in the external skeleton of manyinvertebrates, such as this lobster.