2/18/15

The steps of glycolysis

PLEASE WATCH THIS VIDEO THAT I'VE MADE ABOUT GLYCOLYSIS :)

Step 1:

A phosphate is attached to the glucose molecule. The phosphate comes from ATP, which becomes ADP after donating the phosphate. The enzyme that facilitates this reaction is called hexokinase. When the first step is finished, we have
glucose-6-phosphate.

Step 2:

An isomer of glucose-6-phosphate is created by the enzyme phosphoglucose isomerase. The isomer created is called fructose-6-phosphate.

Step 3:

The enzyme called phosphofructokinase attaches a phosphate from ATP to fructose-6-phosphate. The phosphate is attached on the first carbon of
fructose-6-phosphate, so the product that is formed is fructose1,6-bisphosphate. Of course, ATP donated a phosphate, so it left off as ADP.

Steps 4 and 5:

In the fourth step, the enzyme aldolase splits fructose 1,6-bisphosphate to two three-carbon molecules, which are isomers of each other. These are dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.

In step 5, the enzyme triphosphate isomerase converts dihydroxyacetone phosphate into glyceraldehyde 3-phosphate.

(Remember, since we have now 2 three-carbon molecules, so there is double amount of each product from now. For instance, if one ATP is produced from one three-carbon molecule, there are two ATP molecules produced in total.)

Step 6:

Glyceraldehyde 3-phosphate is converted to 1,3-bisphosphoglycerate. The enzyme that catalyzes this reaction is called glyceraldehyde phosphate dehydrogenase. Hydogen ion is released, and NAD + Pi come in. Pi is donated to the glyceraldehyde 3-phosphate, and it is attached to the 1st carbon. NAD picks up the hydrogen ions. What we get is 1,3-bisphosphoglycerate.

Step 7:

The phosphate is removed from 1,3-bisphosphoglycerate, and 3-bisphosphoglycerate is formed. The phosphate that has been removed is attached to the ADP that comes in, so it becomes ATP. The enzyme that catalyzes this reaction is phosphoglycerate kinase.

Step 8:

The enzyme phosphoglyceromutase removes the phosphate from the third carbon of the 3-phosphoglycerate, and attaches it on the 2nd carbon. Thus, 3-phosphoglycerate becomes 2-phosphoglycerate.

Step 9:

2-phosphoglycerate is converted to phosphoenolpyruvate by enolase. During this reaction, water is released.

Step 10:

Phosphoenolpyruvate (PEP) looses its phosphate. This phosphate is donated to ADP, so it becomes ATP. The enzyme that catalyzes this reaction is called pyruvate kinase. The end product of glycolysis is pyruvate, which is used later in cellular respiration.

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