Which of the following occurs in the mitochondrial matrix? (Choose 2)

The citric acid cycle, also known as the Krebs cycle or TCA cycle, takes place in the mitochondrial matrix. This cycle is a crucial part of cellular respiration, where acetyl-CoA, derived from carbohydrates, fats, and proteins, is oxidized to produce energy. The citric acid cycle generates NADH and FADH2, which then serve as electron carriers that will participate in subsequent stages of energy production, specifically in oxidative phosphorylation.

The mitochondrial matrix is the innermost compartment of the mitochondrion, providing an ideal environment for the enzymes and substrates involved in the citric acid cycle to function effectively. In this space, important substrates are metabolized, leading to the release of carbon dioxide and the production of high-energy electron carriers which are critical for ATP synthesis.

While glycolysis occurs in the cytoplasm and oxidative phosphorylation occurs across the inner mitochondrial membrane, these processes do not take place in the mitochondrial matrix. Similarly, the pentose phosphate shunt primarily occurs in the cytoplasm as well. Therefore, the citric acid cycle stands out as one of the key metabolic processes that happen specifically within the mitochondrial matrix.