Glycolysis Broken Down

Glycolysis can be a pretty daunting concept to really get a firm understanding on, with so many different molecule derivatives involved. So here, I will be explaining this process in a step-by-step manner that hopefully, will help alleviate any frustrations. The main function of the glycolysis pathway, which occurs in the cytoplasm of cells, is to break down glucose into two 3-carbon molecules of pyruvate.

GLYCOLYTIC PATHWAY (STEP-BY-STEP)

1. Initially, Glucose (STARTING PRODUCT) is phosphorylated (given a molecule of phosphate) by ATP with the help of hexokinase (enzyme that facilitates phosphorylation), leading to the molecule, Glucose 6-phosphate.
2. Glucose 6-phosphate is rearranged by an enzyme known as Phosphoglucose isomerase, leading to the molecule Fructose 6-phosphate.
3. Following another phosphorylation, this time by the molecule Phosphofructokinase, Fructose 6-phosphate turns into Fructose 1,6-biphosphate. 
4. The 6 carbon molecule, Fructose 1,6-biphosphate is split into two 3-carbon molecules by an enzyme simply called an Isomerase. The resulting 2 molecules are as follows -- Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate (G3P). -- For the sake of keeping things simple, we are not going to worry about the Dihydroxyacetone phosphate because it is converted into G3P later in another reaction.
5. With that being said, we are left with one molecule to deal with (G3P), which undergoes oxidation, followed by yet another phosphorylation. This leads to the production of two NADH molecules, as well as, two 1,3-Bisphosphoglycerate (BPG) molecules. These reactions occur as a result of the enzyme, Glyceraldehyde 3-phosphate dehydrogenase.
6. Next, the enzyme phosphoglycerate kinase facilitates the removal of phosphate molecules by ADP, resulting in two molecules of 3-Phosphoglycerate (3PG). 
7. Conversion of 3PG by Phosphoglyceromutase, converts the 3PG into 2-Phosphoglycerate (2PG).
8. The enzyme Enolase removes a water molecule (H2O) from each 2PG molecule forming two Phosphoenolpyruvate (PEP) molecules. 
9. Finally, Pyruvate kinase facilitates the removal of two more phosphate molecules from PEP, producing two ATP molecules and two Pyruvate molecules (END PRODUCT).

FOLLOW THE CHART BELOW FOR AN OVERVIEW OF EACH MOLECULE. THIS PICTURE DOES NOT SHOW THE ENZYMES ASSOCIATED WITH EACH STEP; HOWEVER, THESE ARE MENTIONED ABOVE.

                                            


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