Advanced Placement (AP) Biology Practice Exam

Which organelle is known as the site of cellular respiration?

1. Endoplasmic reticulum

2. Mitochondria

3. Golgi apparatus

4. Lysosome

The correct answer is: Mitochondria

The mitochondria are known as the site of cellular respiration because they are responsible for converting energy stored in glucose and other nutrients into adenosine triphosphate (ATP), the cellular energy currency. This process involves a series of biochemical reactions, primarily including glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation, which take place within the mitochondrial matrix and on the inner mitochondrial membrane. Mitochondria contain their own DNA and ribosomes, indicating their unique evolutionary history as once free-living prokaryotes. This organelle plays a crucial role in aerobic respiration, enabling the cell to efficiently produce ATP in the presence of oxygen. By facilitating the breakdown of glucose and the subsequent release of energy, mitochondria are essential for the functioning of eukaryotic cells, which rely on ATP for numerous metabolic processes.