Reactants and Products of Glycolysis - Biochemistry

After glucose is converted into glucose-6-phosphate by hexokinase, glucose-6-phosphate is converted into fructose-6-phosphate. This reaction is catalyzed by phosphoglucose isomerase.

Glycolysis has a net yield of 2 ATP per glucose molecules. The Krebs cycle produces 2 GTP molecules per glucose. The electron transport chain and ATP synthase are the main producers of ATP in cellular respiration. The pyruvate dehydrogenase complex, however, does not yield any ATP (or any other nucleoside phosphates). It simply produces acetyl-CoA from pyruvate, releasing one molecule of carbon dioxide per pyruvate.

In the liver, glucokinase irreversibly converts glucose in the cell to glucose-6-phosphate. Phosphofructose kinase-1 irreversibly converts fructose-6-phosphate to fructose-1,6-bisphosphate. Pyruvate kinase converts phosphoenolpyruvate to pyruvate. All the other enzymes listed catalyze reversible glycolysis reactions.

Fructose can be directly transformed into fructose-6-phosphate by hexokinase.

The reaction turning glyceraldehyde-3-phosphate into 1,3-bisphosphoglycerate is shown below

This step of glycolysis does not hydrolyze or generate ATP, even though a phosphate group was added onto the glyceraldehyde-3-phosphate. The energy released when is reduced to , sometimes referred to as the energy of oxidation (of glyceraldehyde-3-phosphate).

The sixth step of glycolysis involves the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). GAPDH moves a hydrogen onto the electron acceptor An NADH is created for each molecule of G3P formed. A phosphate group from inorganic phosphate instead of ATP replaces the hydrogen group that was taken from G3P. This creates the molecule 1,3-bisphosphoglycerate. Remember that glucose is a six-carbon sugar, and that both G3P and 1,3-bisphosphoglycerate are three-carbon sugars. Thus there are two of each of these three-carbon sugars yielded for each glucose that enters glycolysis.

The seventh reaction of glycolysis is the conversion of 1,3-bisphosphoglycerate into 3-phosphoglycerate. The phosphate group is transferred from 1,3-bisphosphoglycerate onto ADP, yielding ATP. The conversion is catalyzed by the enzyme phosphoglycerate kinase.

One molecule of glucose produces two molecules of pyruvate. During this reaction, two ATP are used (steps 1 and 3) and four ATP are generated (two in step 6 and two in step 9), yielding a net production of 2 ATP per glucose. Also, one NADH is produced per glyceraldehyde-3-phosphate to yield a total of 2 NADH per glucose.

Glucose is a six-carbon molecule, and pyruvate is a three carbon molecule. From the name, we know that glycolysis involves the lysis, or splitting of glucose. As such, the products of glycolysis include two molecules of pyruvate.

Each glucose molecule is converted into two pyruvate molecules, with three carbon atoms each. During glycolysis, two NADH molecules are formed per glucose. Oxygen is not necessary -- one major feature of glycolysis is that it produces energy anaerobically. It yields ATP, with a net gain of two ATP molecules for each glucose consumed.

Two separate steps of glycolysis each create 2 ATP (4 ATP total). However, the first and third steps involved in this process require an input of energy in order to work. Thus, the net yield of ATP from glycolysis is actually only 2 ATP. These ATP are produced via substrate-level phosphorylation.

In the liver, glucokinase irreversibly converts glucose in the cell to glucose-6-phosphate. Phosphofructose kinase-1 irreversibly converts fructose-6-phosphate to fructose-1,6-bisphosphate. Pyruvate kinase converts phosphoenolpyruvate to pyruvate. All the other enzymes listed catalyze reversible glycolysis reactions.

Fructose can be directly transformed into fructose-6-phosphate by hexokinase.

The reaction turning glyceraldehyde-3-phosphate into 1,3-bisphosphoglycerate is shown below

This step of glycolysis does not hydrolyze or generate ATP, even though a phosphate group was added onto the glyceraldehyde-3-phosphate. The energy released when is reduced to , sometimes referred to as the energy of oxidation (of glyceraldehyde-3-phosphate).

Glycolysis, as the name suggests, is the process of lysing glucose into pyruvate. Since glucose is a six-carbon molecule and pyruvate is a three-carbon molecule, two molecules of pyruvate are produced for each molecule of glucose that enters glycolysis. Glycolysis occurs in the cytoplasm of the cell, and does not require oxygen. The net energy production is two ATP per glucose.

After glucose is converted into glucose-6-phosphate by hexokinase, glucose-6-phosphate is converted into fructose-6-phosphate. This reaction is catalyzed by phosphoglucose isomerase.

The sixth step of glycolysis involves the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). GAPDH moves a hydrogen onto the electron acceptor An NADH is created for each molecule of G3P formed. A phosphate group from inorganic phosphate instead of ATP replaces the hydrogen group that was taken from G3P. This creates the molecule 1,3-bisphosphoglycerate. Remember that glucose is a six-carbon sugar, and that both G3P and 1,3-bisphosphoglycerate are three-carbon sugars. Thus there are two of each of these three-carbon sugars yielded for each glucose that enters glycolysis.

The seventh reaction of glycolysis is the conversion of 1,3-bisphosphoglycerate into 3-phosphoglycerate. The phosphate group is transferred from 1,3-bisphosphoglycerate onto ADP, yielding ATP. The conversion is catalyzed by the enzyme phosphoglycerate kinase.

One molecule of glucose produces two molecules of pyruvate. During this reaction, two ATP are used (steps 1 and 3) and four ATP are generated (two in step 6 and two in step 9), yielding a net production of 2 ATP per glucose. Also, one NADH is produced per glyceraldehyde-3-phosphate to yield a total of 2 NADH per glucose.