At which stage is glucose broken into smaller molecules? before cellular respiration begins during the first stage of cellular respiration during the second stage of cellular respiration at the end of cellular respiration

Glycolysis: fructose, 1,5 bisphosphate to glyceraldehyde,3, phosphate

Linked reaction: piruvate to acetyl Coa

(3 carbon to 2 carbon, decarboxylation and dehydrogenation)

Kreb cycle:

Citrate to alpha-ketoglutarate

Alpha-ketoglutarate to succinate

Explanation:

Glycolysis is the procedure when glucose molecules are divided to release energy. The product resulting from this division is called pyruvate. Next, there are some processes that depending of the presence of oxygen, could be one or another. If there's presence of oxygen, the next process is aerobic respiration, otherwise it's anaerobic respiration or fermentation.