Biology and Scientific Research Practice Test 2025 – Your All-in-One Guide to Exam Success!

Mitochondria are often referred to as the powerhouses of the cell due to their primary role in producing adenosine triphosphate (ATP), the energy currency of cells. They achieve this through a process called cellular respiration, which involves a series of biochemical reactions that convert nutrients, primarily glucose, into ATP.

This process occurs in several stages, including glycolysis, the Krebs cycle, and oxidative phosphorylation, with mitochondria being critical for the latter two phases. During these stages, the breakdown of energy substrates results in the generation of ATP, as well as the production of carbon dioxide and water as byproducts.

The other options, such as protein synthesis and photosynthesis, are associated with different cellular processes and structures. For example, protein synthesis primarily occurs in ribosomes and involves translating messenger RNA into proteins. Photosynthesis is a function of chloroplasts in plant cells, where light energy is converted into chemical energy. Nutrient storage is typically a role of vacuoles or specific storage cells, rather than mitochondria. Thus, the defining feature of mitochondria is indeed their crucial involvement in ATP production through cellular respiration.