One mitochondrion contains tens of thousands of copies of each respiratory complex. A single cell contains hundreds or thousands of mitochondria. Your 40 trillion cells contain at least a quadrillion mitochondria, with a combined convoluted surface area of about 14,000 square metres; about four football fields. Their job is to pump protons, and together they pump more than 1021 of them – nearly as many as there are stars in the known universe – every second.
