What is the primary function of mitochondria?

Mitochondria are known as the powerhouse of the cell primarily because their main function is to produce adenosine triphosphate (ATP), which serves as a vital energy currency for cellular activities. This process occurs through cellular respiration, where nutrients are converted into ATP. During this process, mitochondria utilize oxygen to help break down glucose and other molecules, a series of reactions that release energy. This energy is then captured in the form of ATP molecules, which are used by the cell to power a multitude of functions, including muscle contraction, nerve impulse propagation, and biosynthesis of macromolecules.

The other options reflect functions that are characteristic of different cellular structures. For example, support and protection of plant cells are provided by the cell wall, which is not a function of mitochondria. Similarly, the storage of water and maintenance of hydrostatic pressure is primarily the role of vacuoles in plant cells. Lastly, protein synthesis and packaging are mainly handled by ribosomes and the endoplasmic reticulum, not mitochondria. Therefore, the critical role of mitochondria in ATP production distinctly identifies them as key players in energy metabolism within cells.