Which statement correctly defines glycolysis as presented in the material?

• A. The process of breaking down glycogen into glucose to produce energy
• B. The process of breaking down fats into fatty acids
• C. The process of producing energy from proteins
• D. The process of converting glucose to lactate only

Answer: (A)

Glycolysis is the metabolic pathway that converts a single glucose molecule into two pyruvate molecules, yielding a small amount of ATP and NADH in the process. It happens in the cytoplasm and can occur with or without oxygen; when oxygen is scarce, pyruvate can be converted to lactate to regenerate NAD+, allowing glycolysis to continue for quick energy.

The statement describing glycogen breakdown into glucose as the definition of glycolysis mixes up two distinct processes. Glycogenolysis is the breakdown of stored glycogen into glucose units to be used by cells, which can then feed glycolysis, but the act of glycolysis itself is the actual glucose-to-pyruvate pathway. The other option about breaking down fats or proteins refers to lipolysis and proteolysis, which are separate energy-yielding pathways. The idea of glycolysis as converting glucose to lactate only is too narrow; lactate formation is one possible fate of pyruvate under anaerobic conditions, not the defining step of glycolysis itself.