Mitochondria are mainly found in cells that have high energy demands. This includes muscle cells, brain cells, and cells in the heart. In these tissues, mitochondria play a crucial role in producing energy in the form of ATP through a process called oxidative phosphorylation.
In muscle cells, especially those involved in endurance activities, you’ll find a dense population of mitochondria because they require substantial energy to support continuous contractions. Similarly, neurons in the brain rely heavily on mitochondrial energy production to support their constant signaling and maintenance. The heart, being a continuously active muscle, also has a high concentration of mitochondria to ensure it gets the energy needed to pump blood efficiently.
Overall, while mitochondria are present in almost all eukaryotic cells, their abundance reflects the energy needs of that particular cell type.