Glikolízis

Glikolízis is a fundamental metabolic pathway that occurs in the cytoplasm of nearly all living cells. It is the initial process in the breakdown of glucose, a six-carbon sugar, into two molecules of pyruvate, a three-carbon compound. This process does not require oxygen and is therefore considered anaerobic. Glikolízis generates a net gain of two ATP molecules, the primary energy currency of the cell, and two molecules of NADH, an electron carrier that can be used in subsequent energy-producing pathways.

The glikolízis pathway consists of ten enzymatic steps, broadly divided into two phases. The first phase, known as the energy-investment phase, consumes two ATP molecules to destabilize the glucose molecule and prepare it for cleavage. The second phase, the energy-payoff phase, converts the resulting three-carbon molecules into pyruvate, producing four ATP molecules and two NADH molecules. The net result is a gain of two ATP and two NADH per molecule of glucose.

Pyruvate, the end product of glikolízis, can enter several different pathways depending on the availability of oxygen. In the presence of oxygen, pyruvate is further processed through the citric acid cycle and oxidative phosphorylation to generate a much larger amount of ATP. In the absence of oxygen, pyruvate is typically converted into lactate or ethanol through fermentation, regenerating NAD+ which is essential for glikolízis to continue. Glikolízis is a crucial process for energy production, especially in conditions where oxygen is limited, and it provides the building blocks for various biosynthetic pathways.