AP BIOLOGY

Detailed explanation-1: -During NADH regeneration, the two pyruvate molecules are first converted to two acetaldehyde molecules, releasing two carbon dioxide molecules in the process. The two NADH then donate electrons and hydrogen atoms to the two acetaldehyde molecules, producing two ethanol molecules and regenerating NAD+.

Detailed explanation-2: -Fermentation will replenish NAD+ from the NADH + H+ produced in glycolysis. One type of fermentation is alcohol fermentation. First, pyruvate is decarboxylated (CO2 leaves) to form acetaldehyde. Hydrogen atoms from NADH + H+ are then used to help convert acetaldehyde to ethanol.

Detailed explanation-3: -Answer and Explanation: The process that uses oxygen to regenerate NAD+ and FADH for use in respiration is called the electron transport chain. NADH and FADH2 generated during glycolysis and the Krebs cycle are oxidized back to NAD+ and FADH. The electrons are transferred to the electron transport chain.

Detailed explanation-4: -In fermentation reactions, NAD+ molecules pull electrons/H atoms off nutrient molecules (e.g. sugars) and transfer them to pyruvate molecules, forming fermentative endproducts like lactate or ethanol (type of endproduct depends on the type of cell that’s fermenting).

Detailed explanation-5: -Under aerobic conditions, NAD is regenerated when the electrons from NADH molecules are shuttled into the mitochondria and the electron transport chain. The electrons from NADH eventually make their way to molecular oxygen, which is reduced to water.