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

Which process occurs primarily within the mitochondria?

1. Digestion

2. Anaerobic respiration

3. Aerobic respiration

4. Active transport

The correct answer is: Aerobic respiration

The process that occurs primarily within the mitochondria is aerobic respiration. Mitochondria are often referred to as the powerhouses of the cell because they are responsible for producing adenosine triphosphate (ATP), the energy currency of the cell, through aerobic respiration. This process requires oxygen and involves several stages, including glycolysis (which occurs in the cytoplasm), the Krebs cycle, and the electron transport chain, both of which take place inside the mitochondria. Aerobic respiration is vital for efficiently converting biochemical energy from nutrients into ATP, enabling cells to perform various functions. The presence of structures within the mitochondria, such as the inner membrane with its folds (cristae), increases the surface area for the electron transport chain, making this process highly effective in energy production.