In glycolysis, the six-carbon glucose molecule is broken in half into two three-carbon molecules. This process uses
two ATP units and creates four ATP units, for a net production of two ATP molecules. At the end of glycolysis, the
molecules can become lactic acid, or lactate, and exit the cell, or become pyruvate and enter the next part of
anaerobic glycolysis called the tricarboxylic acid cycle.
Three stages: glycolysis, Krebs cycle, and the electron transport chain
Glycolysis--enzymatically converts glucose through several steps into pyruvic acid. May be only the first
phase of aerobic respiration or it may serve as the primary metabolic pathway (fermentation). Provides
significant means to synthesize small mount of ATP anaerobically and to generate pyruvic acid--an
essential intermediary metabolite. Process proceeds along 9 steps. Starts w/glucose. Ends with pyruvic
acid (pyruvate). Each of 9 reactions catalyzed by specific enzyme w/a specific name.
(1) glucose activated by addition of phosphate, results in glucose-6-phosphate.
(2) glucose-6-phosphate then converted to fructose-6-phosphate
(3) phosphate added to fructose-6-phosphate forming fructose diphosphate--more symmetrical and can
be split (which it is) into two 3-carbon molecules. No oxidation-reduction has occured and 2 ATP already
(4) The two 3-carbon molecules are isomers (molecules or molecular compounds similar in that they have
the same molecular formula, however have different arrangements of the atoms or groups of atoms
(functional groups) involved) of each other. Next step converts the one Dihydroxyacetone phosphate
(DHAP) to glyceraldehyde-3-P (G-3-P) resulting in two G-3-Ps.
All subsequent steps happen twice (one to each of the 3-C molecules)
(5) First, the G-3-Ps each receive another phosphate. At same time, 2 NADs in the vicinity are reduced to
NADHs. NADHs will be used in last step of catabolism (the electron transport system) to produce ATP.
In the la