Advanced Placement (AP) Biology Practice Exam

What is a metabolic pathway?

1. A single chemical reaction within a cell

2. A series of reactions leading to a product

3. The process of cellular respiration only

4. A method of enzyme deactivation

The correct answer is: A series of reactions leading to a product

A metabolic pathway refers to a series of interconnected chemical reactions that occur within a cell, ultimately leading to the synthesis of a product or the breakdown of a substrate. Each step in the pathway is typically catalyzed by a specific enzyme, causing the substrate to undergo a transformation that drives the overall process. Metabolic pathways include numerous reactions that work in concert to facilitate important biological processes, such as energy production, biosynthesis of macromolecules, and the breakdown of nutrients. Pathways can be linear, branched, or cyclical in nature, and they are vital for maintaining homeostasis and responding to changes in the cellular environment. This concept encompasses not only pathways like glycolysis and the citric acid cycle, which are essential for cellular respiration, but also pathways involved in photosynthesis, amino acid synthesis, and lipid metabolism, among others. The other choices provide a narrower view of biological processes: a single chemical reaction does not encompass the complexity of a pathway, while cellular respiration is just one type of metabolic pathway and enzyme deactivation does not describe a series of chemical reactions.