Glycolysis via the Embden-Meyerhof-Parnas Glycolytic Pathway

What is glycolysis?

Glycolysis is the almost universal pathway that converts glucose into pyruvate along with the formation of nicotinamide adenine dinucleotide (NADH) and adenosine triphosphate (ATP). It primarily occurs in the cytoplasm of the cell.

Aerobic and anerobic glycolysis

Under aerobic conditions, the pyruvate passes into the mitochondria where it is completely oxidized by O2 into CO2 and H2O and its chemical energy largely conserved as ATP. Pyruvate generated via aerobic glycolysis feeds into the TCA or Krebs cycle.

In the absence of sufficient oxygen, the pyruvate is reduced by NADH via anaerobic glycolysis or fermentation to a wide range of products, routinely lactate in animals and ethanol in yeasts.

Embden-Meyerhof-Parnas glycolytic pathway

The starting molecule for glycolysis is glucose, a simple and abundant sugar found in carbohydrates, which provides the energy for most cells. Carbohydrates synthesized during photosynthesis act as the main storage molecules of solar energy. When ingested, complex carbohydrates are enzymatically hydrolyzed to monosaccharides, such as starch to D(+)-glucose.

The catabolism of glucose is the primary energy source for short-term requirements.

The remainder of this article will focus on the glycolytic pathway known as the Embden-Meyerhof-Parnas (EMP) pathway, named for its discoverers, Gustav Embden, Otto Meyerhof, and Jakub Karol Parnas. The chemical steps of the pathway are illustrated in the image to the right and via the video below.

Click to download glycolytic pathway chart image.

10 steps in the glycolytic pathway and enzymes of glycolysis

The table below outlines the 10 individual reactions of the glycolytic pathway and the enzyme (with IUBMB Enzyme Commission number) that catalyzes each step.

Glycolysis via the Embden-Meyerhof-Parnas glycolytic pathway

Glycolysis animation - video

Enzymes of Glycolysis

2.7.1.1 - Hexokinase
5.3.1.9 - Glucose-6-Phosphase Isomerase
2.7.1.11 - 6-Phosphofructokinase
4.1.2.13 - Fructose-bisphosphate aldolase
1.2.1.12 - Glyceraldehyde-3-phosphate dehydrogenase
2.7.2.3 - Phosphoglycerate kinase
4.2.1.11 - Phosphopyruvate hydratase (enolase)
2.7.1.40 - Pyruvate kinase
1.1.1.27 - Lactate dehydrogenase

Materials
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This article has been expanded from its original form, published in BioFiles 2007, 2.6, 4.