Which organelle is known as the "powerhouse of the cell"?

Mitochondria are referred to as the "powerhouse of the cell" because they are the primary site for the production of adenosine triphosphate (ATP), which is the energy currency of the cell. Through a process called cellular respiration, mitochondria convert nutrients—primarily glucose—into ATP, along with carbon dioxide and water as byproducts. This energy is essential for various cellular processes, including metabolism, growth, and maintenance.

Mitochondria have their own DNA and are involved in other important functions such as the regulation of the cell cycle and apoptosis (programmed cell death). Their role in energy production is critical, as it powers cellular activities and supports the overall function of tissues and organs in multicellular organisms.

In contrast, while the nucleus controls the cell's activities and contains genetic material, and the endoplasmic reticulum is involved in the synthesis and transport of proteins and lipids, they do not directly generate the energy that is crucial for cellular functions. The Golgi apparatus plays a key role in modifying, sorting, and packaging proteins but is not involved in energy production. Therefore, mitochondria uniquely fulfill the role of being the powerhouse of the cell.