There are more mitochondria in muscle cells than there are in skin cells.
Cellular respiration occurs in mitochondria. There are three stages to cellular respiration- Glycolysis, the Krebs cycle, and the electron transport chain (ETC). Each stage of cellular respiration utilizes a different part of the mitochondria. Cellular respiration is the process by which energy is made. During cellular respiration, oxygen gas and the sugar called glucose are transformed into carbon dioxide, water, and an energy source called adenosine triphosphate (ATP).
The number of mitochondria within a cell differs based on the organism, tissue type, or cell type. Cells that are more active and/or move more will require a greater energy produced via cellular respiration. Therefore, cells that are more active usually contain more mitochondria than cells that are not as active. Since muscle cells are required for the movement of an organism, they will have more mitochondria than skin cells.