Advanced Placement (AP) Biology Practice Exam

What is the primary role of glycolysis in cellular metabolism?

1. Converting pyruvate to acetyl-CoA

2. Producing ATP via chemiosmosis

3. Generating NADH from glucose

4. Converting glucose to pyruvate

The correct answer is: Converting glucose to pyruvate

The primary role of glycolysis in cellular metabolism is to convert glucose to pyruvate. This process occurs in the cytoplasm and serves as the foundational step in the catabolism of carbohydrates. Glycolysis involves a series of enzymatic reactions that break down one molecule of glucose into two molecules of pyruvate, along with the production of a net gain of two ATP molecules and two NADH molecules. This pathway plays a crucial role in cellular respiration, as the pyruvate generated can either enter the mitochondria for further oxidation in the presence of oxygen (aerobic respiration) or be converted to lactate or ethanol in anaerobic conditions. In this way, glycolysis is integral to energy production and metabolic pathways in both prokaryotic and eukaryotic cells. While generating NADH is an important aspect of glycolysis, its core function is the conversion of glucose to pyruvate. The other choices either represent subsequent processes in cellular respiration or techniques related to ATP production that occur after glycolysis has taken place.