According to the widely accepted scheme of cellular respiration,...

Glycolysis is the metabolic pathway that converts glucose into pyruvate. It occurs in the cytoplasm of the cell and does not require oxygen. In anaerobic organisms, which lack the ability to utilize oxygen, glycolysis is the only process of respiration that generates ATP. The other pathways, such as the Tricarboxylic acid cycle, Oxidative phosphorylation, and Oxidative decarboxylation of pyruvate, require oxygen and occur in aerobic organisms.

Answer: Glycolysis