Smaller single-celled organisms have a high surface area to volume ratio, which allows them to rely on oxygen and material diffusing into the cell (and wastes diffusing out) in order to survive. The higher the surface area to volume ratio they have, the more effective this process can be.
Due to the larger surface, it allows double the amount of nutirents to enter the cell. The higher the surface area to volume ratio they have, the more effective this process can be.
Electron transport trains create a concentration gradient of hydrogen ions outside the mitochondria and fewer inside the mitochondria and creates energy(ATP) by diffusing the hydrogen ions back in
