How Many Molecules of ATP(Adenosine Triphosphate) are Produced in Glycolysis

Introduction

Glycolysis forms four molecules of ATP (adenosine triphosphate) from one glucose molecule. However, two molecules of adenosine triphosphate are consumed in the first half of glycolysis, which is the energy investment stage. So only two molecules of ATP remain. So a total of 2 ATP and 2 NADH molecules are produced in this process. Edward Buchner first discovered it in 1897 during the fermentation of the yeast cells' broken extracts.

Importance of Glycolysis and ATP:

The glycolysis process is necessary for most living cells from an energy point of view and as a source of precursors for other metabolic pathways.

Glycolysis can occur without oxygen, the condition in which life evolved on Earth and that many contemporary cells, both eukaryotic and prokaryotic, experience. Here are some examples.

In humans and most animals, muscles exhibit activity-dependent anaerobiosis; they can work anaerobically for short periods. For example, when an athlete performs highly intense exercises, his/her need for ATP exceeds the body's ability to supply oxygen to the muscle. In this type of situation, muscles function anaerobically, although for a short period.

There are micro-organisms that live in environments where the oxygen content is near zero, such as deep water and soil. And many types of micro-organisms called obligate anaerobes can't live in the presence of oxygen, a highly reactive molecule. Examples are Clostridium perfringens and Clostridium botulinum, which cause gangrene and tetanus, respectively.

ATP is the output of glycolysis and is consumed for energy in ion transport, muscle contraction, nerve propagation, chemical synthesis, and substrate phosphorylation processes. These processes require a high amount of ATP.

Glycolysis Process:

It is a catabolic pathway, and it occurs in the cytoplasm of cells. In the process of glycolysis, one molecule of glucose is converted into two molecules of pyruvate, two molecules of ATP, two molecules of NADH, and two molecules of water by a sequence of 10 reactions to give energy. This process can take place with or without oxygen.

If oxygen is present, glycolysis is the first stage of cellular respiration, and if oxygen is not available, then glycolysis allows cells to produce small amounts of ATP (adenosine triphosphate) through a fermentation process.

Below is the complete reaction

\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+2 \mathrm{ADP}+2 \mathrm{Pi}+2 \mathrm{NAD}^{+} \rightarrow 2 \mathrm{C}_3 \mathrm{H}_4 \mathrm{O}_3+2 \mathrm{ATP}+2 \mathrm{NADH}_2

Below are the ten steps of glycolysis:

Step 1

• In the cell cytoplasm, a group of phosphate is added to the Glucose

• The group of phosphate is transferred from the ATP to the Glucose, forming Glucose,6-phosphate.

Step 2

Glucose-6-phosphate is converted(isomerised) into fructose

Step 3

The other ATP molecule moves to the phosphate group on fructose 6-phosphate and changes it into fructose 1,6-bisphosphate.

Step 4

The enzyme aldolase produces glyceraldehyde 3-phosphate and dihydroxyacetone phosphate from fructose 1,6-bisphosphate.

Step 5

Triose-phosphate isomerase changes dihydroxyacetone phosphate into glyceraldehyde 3-phosphate. It is the substrate in each successive step of glycolysis.

Step 6

Two reactions happen here-

• The enzyme glyceraldehyde 3-phosphate dehydrogenase moves one H(hydrogen) molecule from glyceraldehyde phosphate to the nicotinamide adenine dinucleotide to form NADH + H+.

• The Glyceraldehyde 3-phosphate dehydrogenase combines a phosphate with the oxidised glyceraldehyde phosphate to make 1,3-bisphosphoglycerate.

Step 7

Phosphate is transmitted from 1,3-bisphosphoglycerate to ADP to make ATP with the help of phosphoglycerokinase. Hence, two molecules of phosphoglycerate and two molecules of ATP are obtained.

Step 8

The phosphate of both phosphoglycerate molecules is transferred from the third to the second carbon to yield the two molecules of 2-phosphoglycerate by the enzyme called phosphoglyceromutase.

Step 9

A water molecule is removed by the enolase enzyme from 2-phosphoglycerate to form phosphoenolpyruvate.

Step 10

A phosphate from phosphoenolpyruvate is transmitted to ADP to produce pyruvate and ATP by the action of pyruvate kinase. 2 molecules of each pyruvate and ATP are obtained as the end products.

Conclusion:

In most of the cells, glycolysis converts glucose to pyruvate, which is then oxidized to CO2 and water. In the absence of oxygen, it is the only means of ATP production from glucose.