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GLYCOLYSIS
Major pathways of glucose utilization.
The two phases of glycolysis.
Three possible catabolic fates of the pyruvate formed in glycolysis.
The Preparatory Phase of Glycolysis Requires ATP
Phosphorylation of Glucose
Conversion of Glucose 6-Phosphate to Fructose 6-Phosphate
Phosphorylation of Fructose 6Phosphate to Fructose 1,6-Bisphosphate
Cleavage of Fructose 1,6-Bisphosphate
Interconversion of the Triose Phosphates
The Payoff Phase of Glycolysis Yields ATP and NADH
Oxidation of Glyceraldehyde 3 Phosphate to 1,3 Bisphosphoglycerate
The glyceraldehyde 3 phosphate dehydrogenase reaction
After 1. formation of the enzyme-substrate complex,2. a covalent thiohemiacetal linkage forms between the substrateand the —SH group of a Cys residue—facilitated by acid-basecatalysis with a neighboring base catalyst, probably a His residue.3. This enzyme-substrate intermediate is oxidized by NAD+ boundto the active site, forming a covalent acyl-enzyme intermediate, athioester. 4. The newly formed NADH leaves the active site and isreplaced by another NAD+ molecule. The bond between the acylgroup and the thiol group of the enzyme has a very high standard freeenergy of hydrolysis. 5. This bond undergoes phosphorolysis (attackby Pi), releasing the acyl phosphate product, 1,3-bisphosphoglycerate.Formation of this product conserves much of the free energy liberatedduring oxidation of the aldehyde group of glyceraldehyde 3-phosphate.
Phosphoryl Transfer from 1,3-Bisphosphoglycerate to ADP
Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate
The phosphoglycerate mutase reaction.
Dehydration of 2-Phosphoglycerate to Phosphoenolpyruvate
Transfer of the Phosphoryl Group from Phosphoenolpyruvate to ADP
The Overall Balance Sheet Shows a Net Gain of ATP
• PASTEUR EFFECT: 15 times, in anaerobic.• REGULATION: allosteric, hormonal, gene
expression• GLYCOLYSIS AND CANCER: (10 times more),
anaerobic glycolysis, low mitochondria, high production of glycolytic enzymes.
SUMMARY
Entry of other sugars into glycolytic pathway
fructose
• Present in free form in many fruits• Hydrolysis of sucrose in the intestines of verts• In muscle and kidney; fructose
phosphorylated by hexokinase to F-6-P
IN THE LIVER
• GLYCERALDEHYDE- triose kinase • DHAP- triose phosphate isomerase
galactose
Lactic acid fermentation
EthanolFermentation
Some TPP-Dependent Reactions