Glycolysis in the Cytoplasm - Mrs. Tuma's Biology Page



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)

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