Advanced Placement (AP) Biology Practice Exam

What is the main function of catabolism?

1. Building complex molecules

2. Breaking down complex molecules into simpler compounds

3. Incorporating energy into molecules

4. Aiding in dehydration synthesis

The correct answer is: Breaking down complex molecules into simpler compounds

The main function of catabolism is to break down complex molecules into simpler compounds. This process is essential for several reasons. Firstly, catabolic reactions release energy stored in the chemical bonds of complex molecules, such as carbohydrates, fats, and proteins, which can then be harnessed for cellular activities. This energy is typically released in the form of ATP (adenosine triphosphate), which cells use to fuel various metabolic processes. Additionally, the breakdown products produced by catabolism, such as amino acids, fatty acids, and simple sugars, can be utilized in anabolic pathways to synthesize more complex molecules when needed. Thus, catabolism not only provides the energy required for biological functions but also contributes to metabolic flexibility by supplying precursors for biosynthesis. Understanding this process is critical for studying metabolism and energy regulation within cells.