Advanced Placement (AP) Biology Practice Exam

Which is the main end product of glycolysis?

1. Acetyl-CoA

2. Pyruvate

3. Lactic acid

4. Glycogen

The correct answer is: Pyruvate

The main end product of glycolysis is pyruvate. During glycolysis, a glucose molecule is broken down through a series of enzyme-catalyzed reactions, resulting in the transformation of glucose into two molecules of pyruvate. This process occurs in the cytoplasm and does not require oxygen, making it an anaerobic pathway. Glycolysis consists of ten steps that ultimately lead to the extraction of energy and the production of substrate-level ATP and NADH. At the end of glycolysis, the production of pyruvate signifies the transition point where, depending on the cellular environment, it can either enter the mitochondria for further processing in aerobic respiration or participate in fermentation pathways in anaerobic conditions. Understanding glycolysis is foundational in cellular respiration, and recognizing pyruvate as the end product highlights its crucial role in metabolic pathways beyond glycolysis, including the Krebs cycle when oxygen is present.