Glycolysis Cycle

Reaction 1

• phosphorylation step where a phosphate group is added to glucose by the enzyme hexokinase as glucose enters the cell

• phosphate group comes from an ATP molecule that donates a single phosphate that results in forming ADP

• phosphate keeps glucose in cell/tags it for use

• glucose becomes glucose-6-phosphate

• on its own not favorable — coupled phosphorylation of glucose with ATP degradation reaction

• SINGLE ARROW

• delta G = -16.7kJ/mol (spontaneous)

Reaction 2

• glucose-6-phosphate is converted from pyranose ring to furanose ring —> becomes fructose-6-phosphate

• catalyzed by enzyme phosphohexose isomerase (changes bonding within the molecule)

• equilibrium arrows — delta G +1.7 kJ/mol BUT can become favorable if high enough glucose-6-phosphate concentration

Reaction 3

• another phosphate is added from another ATP (SECOND INVESTMENT)

• enzyme = phosphofructokinase-1

• becomes = fructose-1,6-bisphosphate

Reaction 4

• 6-carbon glucose splits into 2 3-carbon compounds

• result = GAP (glyceraldehyde 3-phosphate) & DHAP (dihydroxacetone phosphate)

• enzyme = aldolase

• both has phosphate group to keep in glycolysis pathway

• equilibrium arrows

Reaction 5

• DHAP molecule is converted to GAP —> now 2 GAP molecules

• enzyme = triose phosphate isomerase

• end of preparatory phase

Reaction 6

• start of payoff phase

• 2 GAP molecules from glucose

• 2 NAHD molecules are produced (each provides 2.5 equivalents of ATP in ETC) and 2 H+

• energy conversion/phosphate group added (2 Pi and NAD+ added)

• enzyme = glyceraldehyde 3-phosphate dehydrogenase

• product = (2) 1,3-bisphosphoglycerate

Reaction 7

• added phosphate groups and transferred to make 2 molecules of ATP directly (substrate-level phosphorylation)

• enzyme = phosphoglycerate kinase

• product = (2) 3-phosphoglycerate

Reaction 8

• moving phosphate to a different carbon where it is more likely to be added to an ADP

• enzyme = phosphoglycerate mutase

• product = (2) 2-phosphoglycerate

Reaction 9

• removing water and creating double bond to form phosphoenolpyruvate

• enzyme = enolase

• product = phosphoenolpyruvate

Reaction 10

• final phosphate group on each phosphoenolpyruvate is transferred to ADP to make ATP by substrate-level phosphorylation

• product = final molecule of glycolysis ( 2 pyruvate) + 2 ATP

• enzyme = pyruvate kinase