Enzyme Kinetics and Mechanism of Action: A Comprehensive Study, Lecture notes of Biology

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SEMESTER-II

CORE-

[UNIT-I]

Carbohydrates

Lipids

Carbohydrates & Lipids:

• (^) Most abundant biomolecule on Earth.
• (^) Dietary staple around the world. (yields energy on oxidation) = major source of energy.
• (^) Serve as structural & protective function in cell wall of bacteria & plants & in CT of animals. - (^) Storage form of energy (triglycerides) - (^) Provide structural component of membrane. - (^) Serve as pigment (carotene), hormones (steroids), vitamins (A,D,E,K).

POLYSACCHARIDE

(GLYCANS)

HOMO-PS HETERO-PS

1. Starch (storage form of carb in plants)
2. Glycogen (storage form of carb in animals)
3. Cellulose (structural PS in plants)
4. Chitin (structural PS in exoskeleton of insects & crustacea)
   1. GAGs (Glycosaminoglycans in ECM)
   2. Peptidoglycan (in bacterial & algal cell wall)

STORAGE

STRUCTURAL

(Based on function) Stores carbohydrate, release MS when required. Mechanical stability to cells, organs, tissues. (single type of monomer) (2 or more different types of monomers)

Carbohydrates: H ydrates of Carbon (CH2O)n

Abundance of Carbohydrates CARBOHYDRATES: most abundant biomolecule in nature CELLULOSE: most abundant carbohydrate in nature CHITIN: second most abundant carbohydrate in nature GLUCOSE: most abundant monosaccharide in nature FRUCTOSE: most abundant monosaccharide in fruits. sweetest of all sugars. GALACTOSE: least sweet monosaccharide. rarely found in food. SUCROSE: most abundant disaccharide in nature.

Carbohydrates: “saccharide” –Gk: sakcharon, meaning “sugar”

1. Carbohydrates are polyhydroxy aldehydes or ketones , or substances that yield such

compounds on hydrolysis.

2. Many, but not all, carbohydrates have the empirical formula (CH2O)n ; some also contain

nitrogen, phosphorus, or sulfur.

3. Major 3 types: MONOSACCHARIDE: simple sugars, consist of a single polyhydroxy

aldehyde or ketone unit. The most abundant monosaccharide in nature is the six-carbon sugar D-

glucose , sometimes referred to as dextrose.

OLIGOSACCHARIDE: consist of two to ten monosaccharide units, joined by

characteristic linkages called glycosidic bonds. The most abundant are the disaccharides , with

two monosaccharide units. Typical is sucrose (cane sugar). ( All common monosaccharides and

disaccharides have names ending with the suffix “-ose.”)

POLYSACCHARIDE: are sugar polymers containing more than 20 or so

monosaccharide units, and some have hundreds or thousands of units. Includes cellulose , starch ,

glycogen etc.

Carbohydrates MONOSACCHARIDES DISACCHARIDES^ POLYSACCHARIDES ALDOSES Glucose, galactose, mannose, Ribose etc.

KETOSES

Fructose, Ribulose, Xylulose etc.

(Two MS joined by glycosidic bond).

Sucrose, lactose, maltose etc

HOMOPOLYSACC-

HARIDES

HETEROPOLYSA

-CCHARIDES

Starch, Glycogen, Cellulose, Glycogen. GAGs : Chondroitin sulphate, Keratan sulphate, Heparan Sulphate etc

Monosaccharides:

• (^) Are colorless , crystalline solids that are freely soluble in water but insoluble in

nonpolar solvents. (benzene, toluene, chloroform).

• (^) Include 3 carbon sugars (triose) to 7 carbon sugars (heptoses).
• (^) The hexoses are prevalent in nature.
• (^) Most have a sweet taste.
• They have chiral carbon atoms ( asymmetric carbon ).
• (^) They form stereoisomers ( L & D forms).
• (^) In aqueous solution , form cyclic structures.
• (^) Monosaccharides are reducing agents.