ISSA Nutritionist Practice Exam

Which metabolic pathway primarily occurs in the mitochondria?

1. Glycolysis

2. Krebs Cycle

3. Glycogenesis

4. Fermentation

The correct answer is: Krebs Cycle

The Krebs Cycle, also known as the Citric Acid Cycle or TCA Cycle, primarily takes place in the mitochondria, which are the powerhouse of the cell. This metabolic pathway plays a crucial role in aerobic respiration, where it facilitates the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins into carbon dioxide and high-energy electron carriers like NADH and FADH2. These carriers are essential for the subsequent Electron Transport Chain, also located in the mitochondria, where the majority of ATP is produced. While glycolysis occurs in the cytoplasm and involves the breakdown of glucose without the need for oxygen, and glycogenesis refers to the synthesis of glycogen, which also occurs in the cytoplasm, fermentation is a process that can occur in the absence of oxygen, typically in the cytosol, and results in the production of energy through the partial breakdown of glucose. The unique function of the Krebs Cycle in the mitochondria highlights its significance in utilizing oxygen to maximize energy extraction from macronutrients.