Glycolysis is a fundamental metabolic pathway that occurs in the cytoplasm of all living cells. It breaks down glucose, a six carbon sugar, into two molecules of pyruvate, each containing three carbons. This process generates a net gain of two ATP molecules and two NADH molecules, providing essential energy for cellular functions.
The first phase of glycolysis is called the energy investment phase. During this phase, glucose is phosphorylated by consuming two ATP molecules. This makes glucose more reactive and prepares it for the subsequent breakdown. The glucose molecule is converted to fructose one six bisphosphate, which contains two phosphate groups attached to it.
In the cleavage phase, the six carbon fructose one six bisphosphate molecule is split into two identical three carbon molecules called glyceraldehyde three phosphate, or G3P. Each of these molecules contains one phosphate group. This splitting reaction effectively converts one six carbon sugar into two three carbon units, setting the stage for the energy payoff phase where ATP will be produced.
In the energy payoff phase, each glyceraldehyde three phosphate molecule is converted to pyruvate through a series of reactions. This process generates four ATP molecules and two NADH molecules. Since two ATP were consumed in the investment phase, the net result is a gain of two ATP molecules plus two NADH molecules. The NADH can be used later in cellular respiration to produce even more ATP.
To summarize what we have learned about glycolysis: It is a fundamental metabolic pathway that breaks down glucose into pyruvate in the cell cytoplasm. The process occurs in three phases: energy investment, cleavage, and energy payoff. The net result is a gain of two ATP and two NADH molecules per glucose molecule. This pathway is essential for cellular energy production and the pyruvate produced can enter further metabolic pathways for additional energy generation.