Carbohydrates

Carbohydrates
Carbohydrates : are widely distributed in plants and animals; they have important
structural and metabolic roles. In plants, glucose is synthesized from carbon
dioxide and water by photosynthesis and stored as starch or used to synthesize
cellulose of the plant framework. Animals can synthesize carbohydrate from lipid
glycerol and amino acids, but most animal carbohydrate is derived ultimately from
plants. Glucose is the most important carbohydrate; most dietary carbohydrate
is absorbed into the bloodstream as glucose, and other sugars are converted into
glucose in the liver. Glucose is the major metabolic fuel of mammals (except
ruminants) and a universal fuel of the fetus. It is the precursor for synthesis of all
the other carbohydrates in the body, including glycogen for storage; ribose and
deoxyribose in nucleic acids; and galactose in lactose of milk, in glycolipids, and
in combination with protein in glycoproteins and proteoglycans. Diseases
associated with carbohydrate metabolism include diabetes mellitus, galactosemia,
glycogen storage diseases, and lactose intolerance.
CARBOHYDRATES ARE ALDEHYDE
OR KETONE DERIVATIVES OF
POLYHYDRIC ALCOHOLS
(1) Monosaccharides are those carbohydrates that cannot be hydrolyzed into
simpler carbohydrates: They may be classified as trioses, tetroses, pentoses,
hexoses, or heptoses, depending upon the number of carbon atoms; and as aldoses
or ketoses depending upon whether they have an aldehyde or ketone group.
Examples:
Classification of important sugars.
(2) Disaccharides are condensation products of two monosaccharide units.
Examples are maltose ,lactose and sucrose.