disacchares sucrose inversion of sugar

1. Biochemistry
Lecture no 11- 13
Maria Gul
Lecturer
Jips, Lahore

2. Mutarotation
• A freshly prepared solution of alpha D-glucose or beta D-glucose is
observed in polarimeter.
• Specific rotation is not fixed it goes on changing
• After a specific time it become fixed at +52.7
• On being dissolve in water glucose molecule go on changing from one
to another form, each having different specific rotation.
• 38% alpha D-glucose have specific rotation +112 degree
• 62 % beta D-glucose have specific rotation +19 degree
• Small amount of glucose in aldehyde form
• When heated more and more straight chain formation make it
reducing sugars

4. Sucrose dextrorotatory
• Table sugar
• Non reducing sugar
• Glucopyranose
• fructofuranose both dextrorotatary
• On hydrolysis
• Release into fructopyranose that is levo
• Sucrose become levo
• Levo activity is more than glucose
• In this process rotation has been reversed the process is inversion.
• Product of sucrose hydrolysis is called invert sugar
• Honey is rich in invert sugar b/c honey bees has enzyme invertase
Which convert sucrose into invert sugar
• More sweet than sucrose

5. •Invert sugar specific rotation -19.8
•Sucrose specific gravity (+ 66.5)
•Invertas or sucrase AND HCL are used for
inversion
•IN man PRESENT IN MUCOSAL LINNING OF SMALL INTESTINE

6. POLYSACCHARIDES
lec 12
• Homopolysaccharides
• heteropolysaccharides

7. Homopolysaccharides
• Starch is a homopolymer of glucose forming an
• α-glucosidic chain, called a glucosan or glucan.
• It is the most important dietary carbohydrate in
cereals, potatoes, legumes, and other vegetables.
• Non reducing sugar

8. Hydrolysis
• By acid
• By enzymes

9. • The two main constituents
• Amylose (13–20%), which has a no branching helical
structure, form hydrated micelles which give blue
color with iodine. 50-5000 glucose units.
• amylopectin (80–85%), which consists of branched
chains composed of 24–30 glucose residues united by
α1 → 4 linkages in the chains and by α1 → 6 linkages
at the branch points. 1 million glucose units

11. • The extent to which starch in foods is hydrolyzed by
amylase is determined by its structure, the degree of
crystallization or hydration (the result of cooking), and
whether it is enclosed in intact (and indigestible) plant
cells walls.
• The glycemic index of a starchy food is a measure of
its digestibility, based on the extent to which it raises
the blood concentration of glucose compared with an
equivalent amount of glucose or a reference food such
as white bread or boiled rice.

12. • Lecture 13

13. Glycogen
• Glycogen (Figure 14–13) is the storage polysaccharide in animals and
is sometimes called animal starch. It is a more highly branched
structure than amylopectin with chains of 12–14 α-d-glucopyranose
residues (in α1 → 4 glucosidic linkage) with branching by means of α1
→ 6 glucosidic bonds.

15. • consists of polysaccharide chains, each containing
about 13 glucose residues.
• The chains are either branched or unbranched and are
arranged in 12 concentric layers (only four are shown
in the figure).
• The branched chains (each has two branches) are
found in the inner layers and the unbranched chains in
the outer layer.
• (G, glycogenin, the primer molecule for glycogen
synthesis.)

16. Cellulose
• Cellulose is the chief constituent of plant cell walls. It is insoluble and
consists of β-d-glucopyranose units linked by β1 → 4 bonds to form
long, straight chains strengthened by cross-linking hydrogen bonds.
• Mammals lack any enzyme that hydrolyzes the β1 → 4 bonds, and so
cannot digest cellulose.
• It is an important source of “bulk” in the diet, and the major
component of dietary fiber.
• Microorganisms in the gut of ruminants and other herbivores can
hydrolyze the linkage and ferment the products to short-chain fatty
acids as a major energy source. There is some bacterial metabolism of
cellulose.

17. Inulin
• Inulin is a polysaccharide of fructose (and hence a
fructosan) found in tubers and roots of dahlias,
artichokes, and dandelions.
• It is readily soluble in water and is used to determine
the glomerular filtration rate, but it is not hydrolyzed
by intestinal enzymes.

18. Chitin
• Chitin is a structural polysaccharide in
• the exoskeleton of crustaceans and insects, and also in mushrooms.
• It consists of N-acetyl-d-glucosamine units joined by β1 → 4 glycosidic
bonds