Glycolysis in the Cytoplasm
Oxidation of glucose is called glycolysis. This is a series of
enzyme-catalyzed reactions in the cytoplasm of cells.
(Can also occur in the absence of oxygen)
-splits one molecule of glucose (6 carbon molecule) into two
molecules of a 3-carbon acid - pyruvic acid (pyruvate).
Glycolysis occurs in two phases:
1. Glycolysis I - Energy Investment Phase
ATP is used to split the 6-carbon molecule into two
3-carbon molecules
2. Glycolysis II - Energy Payoff Phase
2 ATP are produced and 2 molecules of the electron
carrier NADH + H+ along with 2 molecules of pyruvate
Pyruvate is an important branch point in metabolism.
There is still a significant amount of potential energy left in
pyruvate:
1. If no oxygen present (anaerobic), then pyruvate enters
fermentation reactions:
i) Some organisms (yeast, bacteria) can produce CO2 and
ethanol by fermentation.
ii) Some organisms (bacteria, us!!) can produce lactic acid
by fermentation.
Both of these reactions make ATP, and regenerate NAD+ to allow
glycolysis to continue.
2. If oxygen is present (aerobic), pyruvate enters the mitochondria,
is converted to acetyl-coenzyme A and enters
the "Citric Acid Cycle" (Krebs Cycle)