Cell Biology · Lesson 9 of 12

Mitochondrion

A warm bowl of oatmeal on a cold morning fills your stomach. An hour later, your legs carry you briskly up three flights of stairs without stopping. The oatmeal didn't push your shoes up the steps on its own. Your body broke down the oats into simple sugars, and your blood carried those sugars straight to your muscles. Inside every working muscle cell, tiny structures take that fuel, combine it with the oxygen you breathe, and turn it into usable motion.

Inside each cell, mitochondria take the chemical energy stored in food and, using oxygen, convert it into ATP, a small molecule the rest of the cell spends to do its work. The inner membrane folds back and forth into ridges, which gives that conversion a large surface to happen on. A hard-working muscle cell can hold thousands of them to keep up with daily effort. People often teach that "Mitochondria are the powerhouses of the cell." But a power plant doesn't generate power out of thin air, and a mitochondrion doesn't make energy out of nothing. It converts the energy already stored in food into a form the cell can use, and some of it is lost as heat on the way. It also carries a small DNA of its own, thirty-seven genes, which you inherit only from your mother.

Therefore

When you hear a catchy label for a cell part, check what it actually takes in and what it gives off. Cells don't create anything from scratch; they simply trade and reshape what enters them.

A small reminder, on a gym locker or a water bottle, that every movement runs on tiny cellular engines passed down from your mother.

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