BIOSYNTHETIC PATHWAYS-MEDICINALLY

IMPORTANT COMPONDS

INTRODUCTION:

METABOLISM

The complex of physical and chemical processes occurring within a living cell or organism that are necessary for the maintenance of life.

In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized.

GLUCOSE CATABOLISM

Glucose will be oxidized by all tissues to synthesis ATP. The first pathway which begins the complete oxidation of

glucose is called Glycolysis.

This pathway cleaves the six carbon glucose molecule (C6H12O6) into two molecules of the three carbon compound

Pyruvate (C3H3O3-).

This oxidation is coupled to the net production of two molecules of ATP/glucose.

RESPIRATION:

Glucose

Glucose-6-P

Pyruvate

Hexokinase

PentosePhosphateShunt

glycolysis

CARBOHYDRATES

Glc-1- phosphate

Glycogen

Cytosol - anaerobic

PyruvateCytosol

Acetyl CoAMitochondria (Aerobic)

Krebs cycle Reducingequivalents

OxidativePhosphorylation(ATP)

AMINOACIDS

FATTY ACIDS

GLYCOLYSIS:

Provide ATP energy Generate intermediates for other pathways

Hexose monophosphate pathwayGlycogen synthesisPyruvate dehydrogenase

Fatty acid synthesisKrebs’ Cycle

Hexokinase

Phosphofructokinase

glucose Glycolysis

ATP

ADP glucose-6-phosphate

Phosphoglucose Isomerase

fructose-6-phosphate

ATP

ADP fructose-1,6-bisphosphate

Aldolase

glyceraldehyde-3-phosphate + dihydroxyacetone-phosphate

Triosephosphate Isomerase Glycolysis continued

Glyceraldehyde-3-phosphate Dehydrogenase

Phosphoglycerate Kinase

Enolase

Pyruvate Kinase

glyceraldehyde-3-phosphate

NAD+ + Pi

NADH + H+

1,3-bisphosphoglycerate

ADP

ATP

3-phosphoglycerate

Phosphoglycerate Mutase

2-phosphoglycerate H2O

phosphoenolpyruvate

ADP

ATP pyruvate

Balance sheet for ~P bonds of ATP: 2 ATP expended 4 ATP produced (2 from each of two 3C fragments from

glucose) Net production of 2 ~P bonds of ATP per glucose.

Glycolysis - total pathway, omitting H+: glucose + 2 NAD+ + 2 ADP + 2 Pi 2 pyruvate + 2 NADH + 2 ATP

In aerobic organisms: pyruvate produced in Glycolysis is oxidized to CO2 via Krebs

Cycle NADH produced in Glycolysis & Krebs Cycle is reoxidized

via the respiratory chain, with production of much additional ATP. 

ANAEROBIC ORGANISMS LACK A RESPIRATORY CHAIN

C

C

CH 3

O

O

O

C

CH 3

O HC

CH 3

OH H

H

N A D H + H + N A D +CO 2

P y r u v a t e A l c o h o l D e c a r b o x y l a s e D e h y d r o g e n a s e

p y r u v a t e a c e t a l d e h y d e e t h a n o l

Some anaerobic organisms metabolize pyruvate to ethanol, which is excreted as a waste product.

NADH is converted to NAD+ in the reaction catalyzed by Alcohol Dehydrogenase.

CITRIC ACID CYCLE Phase Two of oxidation of Glucose

1953 Nobel Prize in Medicine and Physiology

THE FATE OF PYRUVATE AND THE TCA CYCLE

Under aerobic conditions pyruvate is decarboxylated to acetate.

Acetate is oxidized further in the citric acid cycle. A series of oxidation reduction reactions results in the

formation of CO2 from acetate and the transfer of electrons producing NADH and FADH2.

The reducing potential (NADH and FADH2) harvested from the TCA cycle is used to drive the phosphorylation of ADP → ATP

The decarboxylation of pyruvate, and the oxidation of acetate takes place in the mitochondrial matrix.

ATP synthesis takes place in the inner membrane.

KREBS CYCLE

The yield for every turn of the cycle is 2CO2, 3NADHs, 1FADH2, and 1GTP.

MEDICINALLY IMPORTANT COMPOUNDS:

Plants have been the source of medicines for thousands of years.

Important medicinal plants used in various systems of medicine, are widely distributed in the world and are of high commercial and economical importance.

COLLECTION OF MEDICINAL COMPOUNDS

Drugs may be collected from wild or cultivated plants.

It is known that the active constituents of medicinal plants are affected by many factors and may vary during the course of plant growth.

Proper time of collection is very important to obtain a drug of

a good quality.

Ex: Alkaloids,Terpenoids, Citric acid, Cocaine,Nicotine etc.

ALKALOIDS

Medicinally the most important Generally, taste bitter (have alkaline, or basic

chemical properties) a group of naturally occurring chemical

compounds which mostly contain basic nitrogen atoms.

"True alkaloids", which contain nitrogen in the heterocycle and originate from amino acids

EXAMPLES OF ALKALOIDSo Morphine

1st to be isolatedAnalgesic, derived from opium poppies

o CocaineFrom the coca plantAn anesthetic, It can use to alleviate hunger, painand it contains vital nutrients.

o CaffeineStimulant in coffee, teaLethal to insects, fungi

Nicotine is an alkaloid found in the nightshade family of plants (Solanaceae) that constitutes approximately 0.6–3.0% of the dry weight of tobacco

Highly toxic, derived from tobacco

Atropinewell-known pupil dialator

cardiac stimulantA cardiac stimulant is a substance which

acts as a stimulant of the heart

TERPENOIDS

All are built of isoprenes (C5H8) Isoprene is exuded by plants in large

quantities

FLAVONOIDS

Water-soluble pigments, found in red wine, grape juice

Intensely studied for cholesterol-reduction

LIGNINS

Add strength to cell wall Waterproof

Aspirin Greeks and native Americans used bark of

willows (Genus: Salix) as analgesic