OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the function of mitochondria in aerobic respiration?

1. They make glucose

2. They produce oxygen

3. They contain enzymes where aerobic respiration occurs

4. They regulate pH levels

The correct answer is: They contain enzymes where aerobic respiration occurs

Mitochondria are often referred to as the "powerhouses" of the cell because they play a critical role in aerobic respiration, a process that generates ATP (adenosine triphosphate), the main energy currency of the cell. The correct choice emphasizes that mitochondria contain enzymes that facilitate the various biochemical reactions of aerobic respiration. Within mitochondria, the Krebs cycle and oxidative phosphorylation occur, both of which are essential stages of aerobic respiration. The enzymes involved in these processes help break down glucose into carbon dioxide and water, releasing energy stored in chemical bonds, which is then used to produce ATP. In contrast, the other options do not accurately represent the primary role of mitochondria in aerobic respiration. Mitochondria do not synthesize glucose or produce oxygen directly; instead, they use the products of glucose metabolism to generate energy. Additionally, while cellular pH levels are important for metabolic processes, the regulation of pH is not a function specific to mitochondria. Thus, the role of mitochondria in housing enzymes for aerobic respiration is the most accurate and significant feature related to their function in energy production.