CARBOHYDRATES

Karaganda 2014y.

KARAGANDA STATE MEDICAL UNIVERSITY

Brief contents.1. Carbohydrates. Classification. A biological role.2. Monosaharidy-pentose, aldose, ketose.4. Chemical properties monosaccharides.5. Аминосахара their properties, the basic representatives.6. Separate representatives monosaccharides: glucose, fructose, a biological

role.

CARBOHYDRATES

Formerly the name "carbohydrate" was used in chemistry for any compound with the formula

Cm(H2O)n

Monosaccharide

Disaccharides

Oligosaccharides and polysaccharides

MONOSACCHARIDES

Monosaccharides are the simplest carbohydrates in that they cannot be hydrolyzed to smaller

carbohydrates. They are aldehydes or ketones with two or more hydroxyl groups.

If the carbonyl group is an aldehyde, the monosaccharide

is an aldose.

If the carbonyl group is a ketone, the

monosaccharide is a ketose.

D - RIBULOSE

D - FRUCTOSE

OXIDATION

• As noted above, sugars may be classified as reducing or non-reducing based on their reactivity with Tollens', Benedict's or Fehling's reagents. If a sugar is oxidized by these reagents it is called reducing, since the oxidant (Ag(+) or Cu(+2)) is reduced in the reaction, as evidenced by formation of a silver mirror or precipitation of cuprous oxide. The Tollens' test is commonly used to detect aldehyde functions; and because of the facile interconversion of ketoses and aldoses under the basic conditions of this test, ketoses such as fructose also react and are classified as reducing sugars.

REDUCTION

Sodium borohydride reduction of an aldose makes the ends of the resulting alditol chain identical, HOCH2(CHOH)nCH2OH, thereby accomplishing the same configurational change produced by oxidation to an aldaric acid.

Derivatives of HOCH2(CHOH)nCHO

HOBr Oxidation → HOCH2(CHOH)nCO2H an Aldonic Acid

HNO3 Oxidation → H2OC(CHOH)nCO2H an Aldaric Acid

NaBH4 Reduction → HOCH2(CHOH)nCH2OH an Alditol

OSAZONE FORMATION

CHAIN SHORTENING AND LENGTHENING

DISACCHARIDES

MALTOSE: 4-O-α-D-Glucopyranosyl-D-glucose (the beta-anomer is drawn)

CELLOBIOSE: 4-O-β-D-Glucopyranosyl-D-glucose (the beta-anomer is drawn)

LACTOSE, a disaccharide composed of one D-galactose molecule and one D-glucose molecule, occurs naturally in mammalian milk.

SUCROSE, also known as table sugar, is a common disaccharide. It is composed of two monosaccharides: D-glucose (left) and D-fructose (right).

STARCH

α –amylose

α –amylopectin

α –amylose

α –amylopectin