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
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