Instead of many small ones, why does a cell not have a single giant mitochondrion? How does this relate to the concept of surface area?
(how) This relates to the concept of surface area because the inner membrane of a mitochondrion is folded into finger-like projections called cristae. These cristae increase the surface area for chemical reactions and facilitate energy production. Having many small mitochondria maximizes the total inner membrane surface area available, ensuring sufficient energy is supplied for most cellular activities.
(why) A cell does not have a single giant mitochondrion because many small mitochondria provide a much larger total surface area for cellular processes than one giant one would. This allows the cell to efficiently produce the energy required for its activities.
Explanation
The textbook context explains that mitochondria are the 'powerhouses of the cell' that supply energy. It specifically notes that the inner membrane has folds called cristae which 'increase the surface area for chemical reactions and facilitate energy production'. Therefore, many small mitochondria offer a greater total inner membrane surface area (and thus more cristae) than a single giant mitochondrion of the same volume, optimizing the cell's energy production.