The initial breakdown product of glucose is pyruvate, a three-carbon molecule, and this process occurs in the cytoplasm of cells.

The initial breakdown product of glucose is pyruvate, a three-carbon molecule, and this process occurs in the cytoplasm of cells. Glycolysis, the first stage of cellular respiration, takes place in the cytoplasm and involves the enzymatic conversion of one molecule of glucose into two molecules of pyruvate. During glycolysis, a series of chemical reactions lead to the production of a small amount of ATP and NADH. While pyruvate enters the mitochondria for further stages of cellular respiration, glycolysis itself occurs in the cytoplasm, illustrating the initial breakdown of glucose into smaller metabolites to release energy for cellular processes.