DISACCHARIDES

DISACCHARIDES

• Sugars composed of two mono saccharide units joined by α -Glycosidic bond.

• MALTOSE14

• SUCROSE 12

• LACTOSE 14

• LACTULOSE14

• TREHALOSE11

MALTOSE

• COMPOSITION • O α- D- Glucopyranosyl (1-4) α-D-

Glucopyranosyl • MALT sugar• SOURCES • Malt, germinating cereals, enzymatic

hydrolysis of starch by salivary & pancreatic Amylases.

• Maltase enzyme hdrolyzes Maltose into Glucose.

• strong reducing agent.• Shows muta rotation.• Forms sun flower shaped Osazone crystals.

ISOMALTOSE• Enzymatic hydrolysis of branch points of the

AMYLOPECTIN unit of Starch.

• Shows α-(1-6) linkage.

LACTOSE

• SOURCES

• Milk ,pharmaceutical preparations.

• COMPOSITION

• O-β -D- Galactopyranosyl (1-4)-β- D- Glucopyranosyl

• Synthesized in mammary glands ,can appear in the urine of lactating mothers.---LACTOSURIA.

• COW S’ milk contains 45% Lactose.

• Human milk contains 74% Lactose.

• Reducing sugar ,shows muta rotation.

LACTOSE INTOLERANCE

• Lactase deficiency

• Diarrhea ,flatulence , dehydration .

• Treatment

• Stop breast feeding/ milk intake.

• Yoghurt ,cheese & green vegetables for Ca++

intake.

• Lactase pills.

LACTULOSE• O-α –D Galactopyranosyl (1-4 )-β-D Fructopyranosyl

• SOURCES

• Heated Milk , synthetically produced .

• Can not be hydrolyzed by intestinal enzymes .

• Fermentation by intestinal bacteria .

• USES

• Mild Diuretic /osmotic laxative .

SUCROSE (TABLE SUGAR )

• O α -D –Glucopyranosyl (1-2) β- D- fructofuranose

sources

• Cane ,beetroot,sorgham,fruits & vegetables.

• Non reducing sugar ,

• Does not form Osazone crystals.

• Does not exhibit muta rotation .

• Dextro rotatory sugar ( + 66.5 )

• On hydrolysis it becomes strongly Levorotatory (- 28.2)

• INVERT SUGAR• Hydrolytic products of Sucrose are called invert sugars.• Sucrose hydrolysis by Sucrase/ dilute acids liberates

one molecule each of α D- Glucopyranose & β –D Fructofuranose.

• β D- Fructofuranose form is unstable & immediately gets converted to β –D Fructopyranose form, which is strongly Levorotatory ( -92 )

• Overall effect is INVERSION of dextro rotatory Sucrose (+66.5) to Levorotatory.( - 22.8)

• Invert sugars are 33% more sweet than Sucrose i.e. Honey

TREHALOSE

• O α-D Glucopyranosyl (1-1) α-D Glucopyranosyl

• SOURCES

• Fungi, yeast

OLIGO SACCHARIDES

• 3-10 carbohydrate units.

• Components of integral membrane proteins, present on their extra cellular domain.

• Mostly contain Mannose /Sialic acid residues.

• Help in degradation of these integral proteins.

• EXAMPLES

• Glycoproteins

• Antibodies

• Coagulation factors