Carbohydrates

Carbohydrates • •

Carbon based cpds called sugars and starches Found in all living cells • String of C atoms to which atoms of H, O2 are attached in the ratio of 1:2:1 of C, H and O2 •

When burnt leaves black residues of C condensing water at the top of the tubes ie sugar decomposed into C and water • Sugar: simplest CHO, sweet tasting contain suffix ose. • Starch: complex, granular powdry CHO found in seeds,bulbs & tubers of plants eg. Glycogen, cellulose and pectin

Classification • • • • • • • • • •

Monosachharides Disaccharides - Oligosaccharides Polysaccharides Monosaccharides: CHO that can not be further degraded by hydrolysis 3C- Triose 4C- Tetrose 5C- Pentose 6C- Hexose 7C- Heptose Eg. Glucose, fructose and ribose

Oligosaccharides • • • • • •

When hydrolysed give 2 to 6 monosacc’ units. Oligo means ‘few’ but more than 10 or 12 monosacc’ units r found in oligosacc’ Most common oligosacc’ are sucrose, beta lactose and β maltose Sucrose : 1 glucose + 1 fructose unit. Found in beets, sugar, sorghum plants, fruits & veg. β Lactose: 1 galactose + 1 glucose unit. Found in milk β Maltose : 2 units of glucose. Found in germinating seeds but relatively rare.

Polysaccharide

• Contain many monosacc’ units linked together. • Most abundant CHO • Types of polysacc’: α linked polysac’ and β linked polysac’ • α linked polysaccharides: more digestible than than β linked polysacc’ • Animals use α linked polysaccharides but only few animals use β linked polysacc’ • Cellulose utilizing animals (cattle,sheep, termites) use β linked polysacc’- because of the m.o present in their digestive tract. • Polysacc’ make up 60-90% of dry weight of plants but very smaller amt in animals

Polysaccharide • • • • • • •

Eg. of polysacc’: starch in seed and tubers Cellulose in structural material of plants Glycogen in animals Characteristics: White solid materials slightly soluble Not sweet, not reactive chemically because of the active gps. (aldehyde and ketones are tied up bet. Monosacc’ units. So strong acids and enzymes r needed for hydrolysis to release monosacc’ • Types: • Homopolysacc’: Polsacc’ containing only one type of monosacc’ • Hetero polysacc’: Polsacc’ containing more than one type of monosacc’

Homo and Hetero Polysaccharides • • • • • • •

Eg. Of homopolysacc’ : Glycogen: present mainly in liver and muscle of animals Cellulose: made up of glucose units which are β-linked, tough , indigestible Chitin: tough outer covering of many insects and of crustaceans like crabs and lobster. Eg. Of heteropolysacc’ : Pectins: present in apple and milk use in making jam and jelly Mucopolysacc’: contain uronic acid and an amino sugar Hyaluronic acid found in vitreous humor of the eye in the coat of human egg cells