Glycolysis is an important cellular pathway that occurs in almost all organisms. It both consumes and produces cellular energy in the form of ATP and NADH. Clicking on each of the
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The first five steps of glycolysis convert one six-carbon glucose into two three-carbon glyceraldehyde 3-phosphate (G3P) molecules.
To complete this conversion, one molecule of ATP is consumed during step one and step three. Both of these reactions are catalyzed by kinase enzymes and are irreversible.
Because the original glucose molecule is broken down into two G3P molecules, all of the reactions in the second half of gylcolysis occur two times.
This results in two ATPs being produced at both steps 7 and 10. Step 7 is reversible, while step 10 is not.
All of the compounds produced in the second half of glycolysis are made for each of the two molecules of G3P. This includes ATP as well as NADH.
Because two molecules of ATP were consumed in the first half of glycolysis, and four molecules of ATP were produced in the second half, glycolysis results in a net gain of two ATPs.
The NADH created in the second half of glycolysis can be used by other cellular processes such as cellular respiration to produce even more ATP for the cell.