Step 1. Phosphorylation of Glucose
#underbrace("C"_6"H"_12"O"_6)_color(red)("glucose") + "ATP" stackrel("hexokinase")(→) "ADP" + underbrace("C"_6"H"_11"O"_6"P")_color(red)("glucose 6-phosphate")#
Step 2. Isomerization of Glucose 6-Phosphate
#underbrace("C"_6"H"_11"O"_6"P")_color(red)("glucose 6-phosphate") stackrel("phosphoglucoisomerase")( →) underbrace("C"_6"H"_11"O"_6"P")_color(red)("fructose 6-phosphate")#
Step 3. Phosphorylation of Fructose 6-Phosphate
# underbrace("C"_6"H"_11"O"_6"P")_color(red)("fructose 6-phosphate") + "ATP" stackrel("phosphofructokinase")(→) underbrace("C"_6"H"_10"O"_6"P"_2) _color(red)("fructose 1, 6-bisphosphate") + "ADP"#
Step 4. Cleavage into 3-Carbon Fragments
#underbrace("C"_6"H"_10"O"_6"P"_2) _color(red)("fructose 1,6-bisphosphate") stackrel("aldolase")(→) underbrace("C"_3"H"_5"O"_3"P")_color(red)("dihydroxyacetone phosphate") + underbrace("C"_3"H"_5"O"_3"P")_color(red)("glyceraldehyde 3-phosphate")#
Step 5. Tautomerization of the isomers
#underbrace("C"_3"H"_5"O"_3"P")_color(red)("dihydroxyacetone phosphate") stackrel("triose phosphate isomerase")(⇌) underbrace("C"_3"H"_5"O"_3"P")_color(red)("glyceraldehyde 3-phosphate")#
Glyceraldehyde 3-phosphate is on the direct pathway of glycolysis, but dihydroxyacetone phosphate is not.
The enzyme triose phosphate isomerase rapidly interconverts dihydroxyacetone phosphate into glyceraldehyde 3-phosphate so that it can be used to generate #"ATP"#.
The net result for Steps 4 and 5 is
#underbrace("C"_6"H"_10"O"_6"P"_2) _color(red)("fructose 1,6-bisphosphate") → underbrace("2C"_3"H"_5"O"_3"P")_color(red)("glyceraldehyde 3-phosphate")#
Step 6. Oxidative Phosphorylation
#underbrace("2C"_3"H"_5"O"_3"P")_color(red)("glyceraldehyde 3-phosphate") + "2NAD"^+ + "2HP"_i stackrel("glyceraldehyde 3-phosphate dehydrogenase")(→) underbrace("2C"_3"H"_4"O"_4"P"_2)_color(red)("1,3-bisphosphoglycerate")+ "2NADH" + "2H"^+#
Step 7. Formation of #"ATP"#
#underbrace("2C"_3"H"_4"O"_4"P"_2)_color(red)("1,3-bisphosphoglycerate") + "2ADP" stackrel("phosphoglycerokinase")( →) underbrace("2C"_3"H"_5"O"_4"P")_color(red)("3-phosphoglycerate") + "2ATP"#
Step 8. Isomerization of 3-Phosphoglycerate
# underbrace("2C"_3"H"_5"O"_4"P")_color(red)("3-phosphoglycerate") stackrel("phosphoglyceromutase")(→) underbrace("2C"_3"H"_5"O"_4"P")_color(red)("2-phosphoglycerate")#
Step 9. Dehydration of 2-Phosphoglycerate
#underbrace("2C"_3"H"_5"O"_4"P")_color(red)("2-phosphoglycerate") stackrel("enolase") (→) underbrace("2C"_3"H"_3"O"_3"P")_color(red)("2-phosphoenolpyruvate") + "2H"_2"O"#
Step 10. Formation of #"ATP"#
#underbrace("2C"_3"H"_3"O"_3"P")_color(red)("2-phosphoenolpyruvate") + "2ADP" stackrel("pyruvate kinase")( →) underbrace("2C"_3"H"_3"O"_3)_color(red)("pyruvate") + "2ATP"#
Here is a summary of the metabolic pathway:
