EXAM 2

CHEM 433 (unit 2)

step 1 of gluconeogenesis

pyruvate --> oxaloacetate --> PEP, via pyruvate carboxylase and PEP carbokinase (BYPASS)

step 2 of gluconeogenesis

PEP --> 2-phosphoglycerate via enolase

step 3 of gluconeogenesis

2-phosphoglycerate --> 3-phosphoglycerate via phosphoglyceromutase

step 4 of gluconeogenesis

3-phosphoglycerate --> 1,3-bisphosphoglycerate via phosphoglycerate kinase

step 5 of gluconeogenesis

1,3-bisphosphoglycerate --> glyceraldehyde-3-phosphate via GA3P dehydrogenase

step 6 of gluconeogenesis

glyceraldehyde-3-phosphate --> dihydroxyacetone phosphate via triose phosphate isomerase

step 7 of gluconeogenesis

glyceraldehyde-3-phosphate --> fructose-1,6-bisphosphate via aldolase

step 8 of gluconeogenesis

fructose-1,6-bisphosphate --> fructose-6-phosphate via fructose-1,6-phosphatase (BYPASS)

step 9 of gluconeogenesis

fructose-6-phosphate --> glucose-6-phosphate via phosphoglucose isomerase

step 10 of gluconeogenesis

glucose-6-phosphate --> glucose via glucose-6-phosphatase (BYPASS)

Stage 1 (rxns 1-5) of Glycolysis

energy investment; consumes 2 molecules of ATP

Stage 2 (rxns 6-10) of Glycolysis

energy return; generates 4 molecules of ATP and 2 molecules of NADH

Step 1 of glycolysis

Glucose + ATP results in Glucose 6-phosphate + ADP + H+

Step 1 enzyme

Hexokinase

Rxn 1 of Glycolysis

- Traps G6P inside the cell bc the charged phosphate group acts as a molecular marker that cannot cross the plasma membrane

- Classified as isomerization (I) and Far-from-equilibrium (F)

Step 2 of glycolysis

Glucose 6-Phosphate changes to form Fructose 6-phosphate

Step 2 enzyme

Phosphoglucose Isomerase

Rxn 2 of glycolysis

- Classified as isomerization (I) and Near-Equilibrium

Step 3 of glycolysis

Fructose 6-Phosphate + ATP results in Fructose 1,6-biphosphate + ADP + H+

Step 3 enzyme

Phosphofructokinase

Rxn 3 of glycolysis

- Second priming step: an example of bisphosphorylation

- Classified as phosphorylation (P) and Far-from-Equilibrium (E)

Step 4 of glycolysis

Fructose 1,6-biphosphate splits to form glyceraldehyde 3-phosphate + dihydroxyacetone phosphate

Step 4 enzyme

Aldolase

Rxn 4 of glycolysis

- Classified as C-C bond cleavage (C) and Near-Equilibrium

Step 5 of glycolysis

Dihydroxyacetone phosphate rearranges to form glyceraldehyde 3-phosphate

Step 5 enzyme

Triose Phosphate Isomerase

Rxn 5 of glycolysis

- Classified as isomerization (I) and Near-equilibrium (E)

Step 6 of glycolysis

Glyceraldehyde 3-phosphate + NAD+ + phosphate group results in 1,3-biphosphoglycerate + NADH + H+

Step 6 enzyme

Triose Phosphate Dehydrogenase

Rxn 6 of glycolysis

- creates a high-energy acyl phosphate bond in 1,3-BPG with a large standard free energy of hydrolysis

- classified as oxidation (O), phosphorylation (P), and Near-equilibrium (E)

Step 7 of glycolysis

1,3-biphosphoglycerate + ADP results in 3-phosphoglycerate + ATP

Step 7 enzyme

Phosphoglycerate Kinase

Rxn 7 of glycolysis

- Catalyzes the first substrate-level phosphorylation step in glycolysis, producing +2 ATP per glucose

- Classified as ATP-making (A), phosphorylation (P), and Near-equilibrium (E)

Step 8 of glycolysis

3-phosphoglycerate rearranges to form 2-phosphoglycerate

Step 8 enzyme

Phosphoglycerate Mutase

Rxn 8 of Glycolysis

- involves an internal group transfer (not a simple isomerization) mediated by a phosphorylated active-site histidine residue and a transient 2,3-bisphosphoglycerate (2,3-BPG) intermediate

- Classified as Near-equilibrium (E)

Step 9 of glycolysis

2-phosphoglycerate results in a water molecule and phosphoenolpyruvate

Step 9 enzyme

Enolase

Rxn 9 of glycolysis

- Uses Lys345 as a general base, Glu211 as a general acid, and active-site Mg2+ ions to electrostatically stabilize negative charges on the enolate intermediate

- Classified as Dehydration (D) and Near-equilibirum (E)

Step 10 of glycolysis

Phosphoenolpyruvate + ADP + H+ results in pyruvate + ATP

Step 10 enzyme

Pyruvate Kinase

Rxn 10 of Glycolysis

- Catalyzes the second substrate-level phosphorylation step, producing +2 ATP per glucose. Strongly exergonic bc enolpyruvate spontaneously undergoes enol-to-keto tautomerization to form keto-pyruvate, creating a much lower-energy product.

- Classified as ATP-making (A) and Far-from-equilibrium