Final answer:
Not every cell contains mitochondria, but for those eukaryotic cells that do, mitochondria are crucial for ATP production through the process of cellular respiration.
Step-by-step explanation:
Not all cells have mitochondria; notably, mature red blood cells lack these organelles. However, mitochondria are indeed key to energy production within many eukaryotic cells.
Explanation
Mitochondria are often referred to as the powerhouses or energy factories of the cell due to their role in making adenosine triphosphate (ATP), which is the cell's main energy-carrying molecule. The process of creating ATP is known as cellular respiration. During cellular respiration, mitochondria utilize oxygen and produce carbon dioxide as a waste product. The energy-rich molecule ATP is utilized throughout the cell to power various biochemical reactions, including muscle contractions and nerve impulse transmission.
Cells that are highly active and require substantial amounts of energy, such as muscle cells, tend to contain many mitochondria. These structures contain their own DNA and can replicate within the cell to meet the increased demand for energy.