______ is/are known as the powerhouse of the cell.

Mitochondria

The correct answer is Option (4) - Mitochondria

Mitochondria are known as the powerhouse of the cell because they play a crucial role in generating the majority of the cell's energy in the form of adenosine triphosphate (ATP) through a process called cellular respiration.

Within mitochondria, complex biochemical reactions occur, including the citric acid cycle (also known as the Krebs cycle) and the electron transport chain. These reactions involve the breakdown of glucose and other organic molecules obtained from nutrients, leading to the production of ATP.

ATP serves as the primary energy currency of the cell, providing the energy necessary for various cellular processes, including metabolism, growth, movement, and signaling. Without ATP generated by mitochondria, cells would be unable to perform essential functions and would ultimately cease to function.

Therefore, mitochondria are often referred to as the powerhouse of the cell due to their central role in producing energy to fuel cellular activities.