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Glycolysis Pathway in Detail: How Glucose is Turned into Energy

The Glycolysis Pathway

The glycolysis pathway is a sequence of biochemical reactions that convert glucose into energy.

In this blog post, we will discuss the main steps of glycolysis and what products are produced as a result of the glycolytic pathway. We will also take a look at some of the diseases that can be caused by problems with this pathway.

What is Glycolysis?

The glycolysis pathway is important for the production of energy in cells. Glycolysis occurs in the cytoplasm of the cell and provides the cell with a steady supply of ATP (adenosine triphosphate), which is essential for cellular function. Without glycolysis cells fail to survive. There are two types of glycolysis: aerobic and anaerobic. Aerobic glycolysis occurs in the presence of oxygen, while anaerobic glycolysis does not require oxygen.

Main Steps Involved In The Glycolysis Pathway

There are three main steps in glycolysis: substrate level phosphorylation, conversion of glucose-phosphate to fructose-phosphate, and the formation of two molecules of phosphate. In addition, there are several intermediate steps that occur between these three main steps such as the conversion of fructose-bisphosphate to glyceraldehyde-phosphate and the conversion of dihydroxyacetone phosphate to glycerol-phosphate.

Steps involved in the glycolysis pathway (click to enlarge). To download click here!

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Enzymes Involved In Glycolysis

There are several enzymes involved in glycolysis which help to catalyze the various steps of the glycolytic pathway. The enzymes involved in glycolysis are typically found in the cytoplasm of cells.

Enzyme Function

Hexokinase/glucokinase

Catalyzes the conversion of glucose to glucose-phosphate

Phosphofructokinase

Catalyzes the conversion of fructose-phosphate to fructose-bisphosphate

Aldolase

Cleaves fructose-bisphosphate into two molecules of glyceraldehyde-phosphate

Triose phosphate isomerase

Converts glyceraldehyde-phosphate to dihydroxyacetone phosphate

Enolase

Converts dihydroxyacetone phosphate to phosphoenolpyruvate

Pyruvate kinase

Catalyzes the conversion of phosphoenolpyruvate to pyruvate.

Products of Glycolysis and Downstream Effects

The products of glycolysis include pyruvate, NADH, and ATP.

  • Pyruvate is an important molecule that is used in several different pathways in the body. Pyruvate is produced as a result of the conversion of glucose to two molecules of acetyl-CoA. After formation of pyruvate, it is further converted to acetyl-coenzyme A (acetyl-CoA) in the citric acid cycle. The citric acid cycle is also known as the Krebs cycle, and it is responsible for the production of ATP from acetyl-CoA. In the absence of oxygen, pyruvate is converted into lactate. Lactic acid fermentation is an important process that helps to produce ATP in muscles.

  • NADH is a coenzyme that helps to transfer electrons in the electron transport chain. NADH is produced as a result of the reduction of nicotinamide adenine dinucleotide (NAD+) to NADH.

  • ATP is the main source of energy for cells. ATP is produced as a result of the transfer of phosphate groups from glucose-phosphate to ADP. In glycolysis, two molecules of ATP are used to convert glucose into energy. However, four molecules of ATP are produced as a result of this pathway. This means that there is a net production of two ATP in glycolysis.

Diseases Associated with the Glycolytic Pathway

Dysfunctional glycolysis can lead to problems with the production of energy. ATP is essential for cellular function, and problems with its production can lead to symptoms such as weakness, fatigue, and muscle pain. Diseases that can be caused by problems with glycolysis include diabetes, cancer, and heart disease.

Deficiency in glycolytic enzymes such as hexokinase can lead to diabetes. Defects in pyruvate kinase can also lead to heart disease. The glycolysis pathway is important for the survival of tumor cells. Cancer cells often rely on glycolysis for energy because the Warburg effect allows them to bypass oxidative phosphorylation.

Diseases caused due to overactive glycolytic pathway are less common, but they can be very serious. Overactive glycolysis can lead to lactic acidosis, which is a build-up of lactate in the blood. Lactic acidosis can be caused by problems with the enzymes that are involved in glycolysis or by a lack of oxygen. Lactic acidosis can lead to serious health problems such as coma and death.

Written by Colm Ryan

Colm Ryan PhD is a co-founder of Assay Genie. Colm carried out his undergraduate degree in Genetics in Trinity College Dublin, followed by a PhD at the University of Leicester. Following this Colm carried out a post-doc in the IGBMC in Strasbourg, France. Colm is now Chief Executive Officer at Assay Genie.

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