Question

Is ATP is made anywhere else in the body besides the mitochondrion and where?

Answer 1

The most important cellular site for ATP (adenosine triphosphate) synthesis in the eukaryotic organisms including humans is the mitochondria of the cell.

However, ATP can also be synthesized in the cytoplasm of the cells by a process called glycolysis. It is also known as EMP (Embden-Meyerhoff-Parnas) pathway.

In glycolysis, glucose molecule ( 6 carbon atoms ) is broken down into pyruvate ( 3 carbon atoms ) and the energy released is stored in the form of high energy molecules called ATP. In glycolysis 2 ATP molecules along with 2 NADH (reduced nicotinamide adenine dinucleotide) + H+ are produced per molecule of glucose.

This, 2 NADH + H+ later produces 3 ATP molecules by shuttling their electrons and protons to produce 2 FADH2. So a total of 5 ATP molecules are produced in glycolysis but in cytoplasm only 2 ATP molecules per molecule of glucose as the 3 ATP molecules from 2 FADH2 are produced in via the electron transport chain in the mitochondria. Glycolysis can take place both in presence and absence of oxygen, thus it is not dependent on oxygen. Hence, along with eukaryotic cells, it is also found in more primitive prokaryotic cells. Cancer cells also generate their ATP molecules through glycolysis( but at a faster rate) in presence of oxygen (even low oxygen levels are sufficient).

A number of other biochemical pathways are like gluconeogenesis, fatty acid synthesis, cholesterol synthesis, citric acid cycle, pentose phosphate pathway are dependent on glycolysis to get their metabolites from glycolysis.

Thus, an important site for ATP synthesis besides mitochondrion is the cytoplasm of the cells where ATP is produced via glycolysis pathway.