Page 92 - Demo 1

found naturally in milk, is a disaccharide consisng of the monomers glucose
and galactose. The most common disaccharide is sucrose, or table sugar,
which is composed of the monomers glucose and fructose.
Polysaccharides: Energy Storage and Structural Molecules

A polysaccharide is a long chain of monosaccharides linked by covalent
bonds. The chain may be branched or unbranched, and it may contain different
types of monosaccharides. Polysaccharides may be very large molecules.
Starch, glycogen, cellulose, and chin are examples of polysaccharides.

Starch is the stored form of sugars in plants and is made up of amylose
and amylopecn (both polymers of glucose). Plants are able to synthesize
glucose, and the excess glucose is stored as starch in different plant parts,
including roots and seeds. The starch that is consumed by animals is broken
down into smaller molecules, such as glucose. The cells can then absorb the
glucose.

Glycogen is the storage form of glucose in humans and other
vertebrates. It is made up of monomers of glucose. Glycogen is the animal
equivalent of starch and is a highly branched molecule, usually stored in liver
and muscle cells. Whenever glucose levels decrease, glycogen is broken down
to release glucose.

Cellulose is one of the most abundant of all carbohydrates. The cell
walls of plants are mostly made of cellulose, which provides structural support
to the cell. Wood and paper are made up of cellulose. Cellulose is made up of
glucose monomers that are linked by bonds between parcular carbon atoms
in the glucose molecule.

The digesve system of animals is unable to hydrolyze cellulose;
however, some microorganisms can digest it. Ruminants or cud-chewing
animals like cows, buffalos, and horses have an internal pouch called rumen,
where microorganisms break down cellulose to glucose. In humans, cellulose
serves as a dietary fiber that promotes digesve system health.

Carbohydrates perform other funcons in different animals.
Arthropods, such as insects, spiders, and crabs have an exoskeleton which

84