What process converts glucose into pyruvate?

• A. Citric acid cycle
• B. Glycolysis
• C. Calvin cycle
• D. Fermentation

Answer: (B)

The process that converts glucose into pyruvate is glycolysis. Glycolysis is a series of enzymatic reactions that take place in the cytoplasm of cells and breaks down one molecule of glucose, which is a six-carbon sugar, into two molecules of pyruvate, which are three-carbon compounds. This pathway consists of ten steps and can be divided into two phases: the energy investment phase and the energy payoff phase.

During the energy investment phase, two ATP molecules are consumed to phosphorylate glucose and its derivatives, facilitating subsequent steps. In the energy payoff phase, the process generates four ATP molecules and two NADH molecules through substrate-level phosphorylation and oxidation. The net yield from glycolysis is two ATP molecules and two NADH molecules per glucose molecule, with the final product being pyruvate, which can be further utilized in aerobic or anaerobic respiration depending on oxygen availability.

The other processes mentioned, such as the citric acid cycle and fermentation, do not directly convert glucose into pyruvate. The citric acid cycle occurs after glycolysis and is involved in further oxidizing the products of glycolysis (like pyruvate) to produce energy-rich molecules. The Calvin cycle is part of photosynthesis and involves fixing carbon dioxide into sugars