Final answer:
Mitochondria are the organelles found in cells with a high energy requirement, such as muscle cells and sperm cells. They are responsible for producing ATP, the cell's energy source. Cells that need a lot of energy have a higher concentration of mitochondria.
Step-by-step explanation:
Mitochondria are the organelles that would be present in high numbers in cells with a high energy requirement, such as muscle cells and sperm cells. Mitochondria are responsible for producing most of the cell's energy in the form of ATP (adenosine triphosphate). Cells that require a lot of energy, like muscle cells, have a higher concentration of mitochondria. For example, active human muscle cells may have thousands of mitochondria, while less active cells, like red blood cells, do not have any mitochondria.
In cells with a high energy requirement, such as muscle cells and sperm cells, you would expect to find an abundance of mitochondria. Mitochondria are known as the "power plants" of the cell because they produce most of the cell's energy in the form of adenosine triphosphate (ATP). Particularly, skeletal muscle cells, which are involved in the contraction and movement of the body, contain a high concentration of mitochondria to meet their substantial energy needs. During vigorous activities, such as running a marathon, the leg muscles would have a heightened demand for ATP, and consequently, a higher number of mitochondria would be present to fuel this energy requirement.