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-stage one: hexose phosphorylation

-enzyme: hexokinase

-kinases catalyze transfer of gamma phosphate from ATP to substrate

-phosphoglucose isomerase

-glucose isomerized to fructose

(aldose to ketose conversion)

-anomeric and open chain in equilibrium

-phosphofructokinase

(another kinase reaction)

-stage 2 (hexose to triose)

-aldolase

-reverse of aldol reaction

-triose phosphate isomerase

-only glyceraldehyde 3-phosphate (aldose isomer) used in stage 3 of glycolysis

-thus net conversion is to glyceraldehyde 3-phosphate

-glyceraldehyde 3-phosphate dehydrogenase

-oxidation: aldehyde group oxidized to carboxylic acid

*key reaction for ATP synthesis

-1,3-bisphosphoglycerate is key "high energy" intermediate in glycolysis

-hydrolysis of 1,3-BPG is very favorable: delta G= -11.8 kcal/mol

-phosphoglycerate kinase

-1st ATP generating reaction

-enzyme is a "kinase" (named for reverse reaction)

-yields 2 ATP for every glucose molecule since there are 2 1,3-BPG molecules for each glucose

-phosphoglycerate mutase

-occurs in 2 steps (involves 2,3-BPG)

-enolase

-key step energetically for ATP synthesis

*hydrolysis of product is very favorable: delta G= -14.8 kcal/mol

-enol group is unstable w/ respect to keto group

-pyruvate kinase

-2nd ATP generating reaction

-yields 2 ATP for every glucose molecule

-phosphate transfer allows enol to rearrange to more stable "keto" form