AAMC FL Practice Exam

What is the main product of glycolysis in anaerobic conditions?

1. Carbon dioxide

2. Oxygen

3. Ethanol

4. Lactic acid

The correct answer is: Lactic acid

In anaerobic conditions, the primary goal of glycolysis is to convert glucose into energy, specifically in the form of ATP. Glycolysis itself takes place in the cytoplasm and yields a net of two molecules of ATP, along with two molecules of pyruvate. Under aerobic conditions, pyruvate enters the mitochondria and undergoes further oxidation through the citric acid cycle and oxidative phosphorylation, which produces additional ATP. However, in the absence of oxygen, cells must rely on fermentation processes to regenerate NAD+, which is essential for glycolysis to continue. In humans and many animal tissues, the reduction of pyruvate to lactic acid (also known as lactate) occurs, enabling glycolysis to continue and producing a small amount of energy. This process of converting pyruvate to lactic acid allows the cell to maintain a balance of NAD+/NADH, facilitating the ongoing glycolytic cycle and thereby ensuring continued ATP production, albeit at a lower yield compared to aerobic respiration. Therefore, in anaerobic conditions, lactic acid is the main product resulting from the glycolytic pathway.