Pyruvate enters mitochondria for the Krebs cycle in aerobic respiration, producing ATP, CO2, and water, while lactate production is inefficient and requires liver recirculation.

“so the textbook every textbook says the following when you make pyruvate out of glucose the pyruvate gets shuttled in to the mitochondria and there we undergo the uh kreb cycle where we very very efficiently produce massive amounts of ATP and the only byproduct is carbon dioxide and water and so as we are undergoing uh aerobic respiration we're consuming oxygen and pyruvate generating again incredibly efficient amounts of high volume ATP and outcomes carbon dioxide and water which is what we're breathing out conversely when you take that glucose and you make lactate you do generate ATP but very very little amounts and that lactate now needs to escape the cell make its way into the circulation where it can go back to the liver and be turned back into glucose via the Corey cycle to begin again”