What is the function of mitochondria in a cell?

Mitochondria are often referred to as the "powerhouse of the cell" because their primary function is to generate adenosine triphosphate (ATP), which is the main energy currency of the cell. They do this through a process called cellular respiration, where they convert nutrients, particularly glucose, into energy. Mitochondria have their own DNA and ribosomes, enabling them to carry out specific functions independently, but their most crucial role is energy production.

This explanation highlights why mitochondria are essential for cellular function, as energy is necessary for various biological processes, including muscle contraction, nerve impulse propagation, and biochemical synthesis. The other options provided do not accurately describe the primary role of mitochondria; for instance, while storage of genetic material refers to the nucleus, protein synthesis primarily occurs in ribosomes, and defense against pathogens is typically managed by the immune system.