The first stage of cellular respiration is glycolysis, which literally means “sugar splitting.” Look at the diagram.

The diagram shows two units of ATP breaking down a six-carbon sugar molecule. Then, 2 units of NAD+ are converted to 2 NADH and 4 ADPs are converted into 4 ATPs, and the carbon atoms, which now make up a new substance, move on to the Krebs cycle.

When glucose, a 6-carbon sugar, is broken down during glycolysis, what product forms?

A. 2 molecules of lactic acid, C3H6O3
B. 3 molecules of ethanol, C2H5OH
C. 2 molecules of pyruvic acid, C3H4O3
D. 6 molecules of carbon dioxide, CO2