The conversion of glucose or other hexoses into lactate or pyruvate is called:

• A. glycogenesis
• B. glycogenolysis
• C. gluconeogenesis
• D. glycolysis

Answer: (D)

Glycolysis is the metabolic process that breaks down glucose and other six-carbon sugars into pyruvate, with lactate formation possible when oxygen is limited. This all happens in the cytoplasm and consists of a series of ten enzymatic steps, yielding a net gain of 2 ATP and 2 NADH per glucose molecule. When oxygen isn’t available, pyruvate can be reduced to lactate by lactate dehydrogenase, which regenerates NAD+ needed to keep glycolysis running. This allows cells to produce energy quickly under anaerobic conditions, such as during intense exercise.

Other terms describe different pathways: glycogenesis is the synthesis and storage of glucose as glycogen, glycogenolysis is the breakdown of glycogen to glucose, and gluconeogenesis is the production of glucose from non-carbohydrate sources. These are distinct from glycolysis, which specifically refers to the breakdown of glucose to pyruvate (with possible lactate formation).