AP BIOLOGY

Detailed explanation-1: -Fermentation follows glycolysis in the absence of oxygen. Alcoholic fermentation produces ethanol, carbon dioxide, and NAD+. Lactic acid fermentation produces lactic acid (lactate) and NAD+. The NAD+ cycles back to allow glycolysis to continue so more ATP is made.

Detailed explanation-2: -Lactic acid fermentation converts the 3-carbon pyruvate to the 3-carbon lactic acid (C3H6O3) (see figure below) and regenerates NAD+ in the process, allowing glycolysis to continue to make ATP in low-oxygen conditions.

Detailed explanation-3: -In the process of fermentation the NADH + H+ from glycolysis will be recycled back to NAD+ so that glycolysis can continue. In the process of glycolysis, NAD+ is reduced to form NADH + H+. If NAD+ is not present, glycolysis will not be able to continue.

Detailed explanation-4: -Though there are different types of anaerobic respiration, the one relevant to this question is lactic acid fermentation. In this process, the pyruvate coming from glycolysis is converted into lactic acid. When this happens, NADH is also oxidized back into its non-reduced form.

Detailed explanation-5: -Lactate formed during anaerobic glycolysis enters the gluconeogenic pathway after oxidation to pyruvate by lactate dehydrogenase. After intense exercise, the lactate produced diffuses from the muscle into the blood and is taken up by the liver to be converted into glucose and glycogen.