Answer:
1. NADH
2. NADH
3. NADH
Explanation:
Cellular respiration begins with Glycolysis, in which an investment of 2 ATPs are needed in order to break a carbon-carbon bond in 1 glucose molecule. When the bond is broken, high energy electrons are released and carried by NADH to go to the Electron Transport Chain. The resulting carbon compound, pyruvate, will enter the Krebs Cycle (to produce GTP/ATP as well as NADH and FADH₂ which carries electrons to the electron tranport chain). A net gain of 2 ATP are created. However, if oxygen is not readily available to the cell (and the mitochondria), NADH and pyruvate will enter Lactic Acid Fermentation to free up the NADH so it can continue accepting high energy electrons from the breakdown of glucose in Glycolysis. This will, in turn, continue to create a small, but steady supply of ATP energy which is the 2 ATP generated in the payoff phase of glycolsis.