CLASSIFICATION OF CARBOHYDRATES
CARBOHYDRATE
MONOSACCHARIDE
ALDOSE
GLUCOSE
GALACTOSE
KETOSE
FRUCTOSE
DISACCHARIDE
MALTOSE
LACTOSE
SUCROSE
POLYSACCHARIDE
STARCH
GLYCOGEN
CELLULOSE
STARCH, GLYCOGEN & CELLULOSE
Polysaccharides are ubiquitous in nature.
They are called Homopolysaccharides, when made from same sugars and
Heteropolysaccharides when made from different sugars.
They can be linear or branched. Linear chains are made of α-1→4 bonds and branch is made of
α-1→6 bonds
STARCH
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Is a storage polysaccharide in Plants
MADE OF α – GLUCOSE.
AMYLOSE – Linear, linked by α 1→ 4 bonds. [15 – 20%].
AMYLOPECTIN – Branched, linked by α 1→ 6 bonds. [80 – 85%]
Branch point after every 30 Glc unit.
GLYCOGEN
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Storage polysacc in animals, highly branched. Similar to Amylopectin
Branch point every 8 – 12 Glc units
Has only 1 reducing end but many non-reducing ends
CELLULOSE
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Similar to Amylose, linear but made of β 1→ 4 bonds.
Very long chains – 15,000 – 20,000 Glc units
Can’t be digested because amylase recognises only ‘α’ bonds
Microorganism in gut Trichonympha secretes cellulase, which breaks down
cellulose to short chain FA, a energy source
METABOLISM
Co-ordinated and specific reactions – organised as PATHWAYS…
PRIMARY FUNCTIONS:
• Acquiring and Utilising Energy
• Synthesis of structural components of cell eg Membrane
• Growth & Development
• Removal of waste products
GENERAL CHARACTERISTIC – of BIOCHEMICAL REACTIONS:
 No. of reaction types are few – eg., Hydrolysis, Oxidation-reduction etc.
 One enzyme usually catalyses only One reaction
 Only a few important pathways inside cell – Glycolysis, Gluconeogenesis,
TCA cycle, Urea cycle, β-Oxidation etc.
Anabolic and Catabolic Pathways
CARBOHYDRATES
METABOLISM
GLYCOLYSIS
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Glycolysis is a Amphibolic pathway
It occurs in Eukaryotes & Prokaryotes
It occurs in cytoplasm of cell
Total 10 reactions in 2 phases
End product depends on presence of O2
Pay Off
Preparatory
ENERGETICS:
2 ATP
2 NADH = 6ATP
GLUCONEOGENESIS
Pyruvate Carboxylase & PEP Carboxykinase
function inside mitochondria
CORI CYCLE
HMP Shunt
AIM:
1. To produce NADPH, involved in biosynthetic reactions
2. To produce Ribose-5-P, a precursor for DNA synthesis
HMP Shunt
Phase I
SUMMARY
2) Phase – II
Transketolase & Transaldolase
involved
Phase II
1) Phase – I
NADPH & Rib-5-P produced
TCA CYCLE
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Final pathway for oxidation of CHO, PTN & Lipid
Occurs in Mitochondrial Matrix
End product is Acetyl CoA
Series of dehydrogenation & decarboxylation rxns
Each cycle generates 12 ATP’s
It is amphibolic in nature
FORMATION OF ACETYL COA:
ENERGETICS:
2 NADH = 6 ATP
TCA CYCLE
ENERGETICS:
3 NADH = 9ATP
1 FADH2 = 2 ATP
1 GTP = 1 ATP
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ACONITASE
CITRATE SYNTHASE
TOTAL = 12 ATP
ISOCITRATE dehydrogenase
MALATE dhase
GLUCOSE OXIDATION:
GLYCOLYSIS = 8 ATP
ACETYL CO-A = 6 ATP
KETO GLUTARATE dehydrogenase
FUMARASE
TCA CYCLE = 24 ATP
----------------------TOTAL = 38 ATP
SUCCINATE dhase
SUCCINATE THIOKINASE
AMPHIBOLIC NATURE
GLYOXYLATE CYCLE
MAIN FEATURES:
• A modified form of TCA cycle
• Occurs in Plants – during Germination stage
• Helps to form Glucose from Lipid stores
• Key enzymes – Isocitrate Lyase & Malate synthase
present inside Glyoxysomes.
• Involves participation of 3 compartments inside cell;
glyoxysomes, mitochondria & cytosol
GLYCOGENOLYSIS
• Occurs from non-reducing end.
• Takes place in muscle & liver
• Glucose units enter glycolysis by the help of 3 enz:Glycogen phosphorylase
Glycogen debranching enzyme
Phosphogluco mutase
GLYCOGEN
GLUCOSE – 1 – P
GLUCOSE – 6 – P
GLYCOGENOLYSIS
Glycogen debranching enz reaction
• Acts at a branch point when it’s 4 glc long.
• Transfers a 3 glc unit from branch point to a
longer chain for p’lase action to continue
• Last glc residue at branch removed as well
Phosphogluco mutase reaction
Glc-1-P → Glc-6-P
GLYCOGENESIS
• Starts when UDP-Glc & Glycogenin are available.
• 4 enz involved:a) Phosphogluco mutase
Glc-6-P → Glc-1-P
b) UDP-glucose pyrophosphorylase
Glc-1-P + UTP → UDP-glc + PPi
c) Glycogen synthase – Transfers glc to nonreducing end. Acts until branch is 11 unit
long
d) Glycogen branching enzyme – Transfers 6
or 7 glc from a branch containing 11 glc units to
a more interior position creating a new
branch.
GLYCOGENESIS
c) Glycogen synthase – Transfers glc to non-reducing end. Acts until branch is 11 unit
long
GLYCOGENESIS
d) Glycogen branching enzyme – Transfers 6 or 7 glc from a branch with 11 glc units to
a more interior position creating a new branch.