The structure of cells is very important to their function. Structure includes the cell’s size, its shape, and what organelles it has. Organelles (“little organs”) have different functions too.

Cells have to have a particular structure to work as muscle cells. They need long protein fibers that can slide past each other so that the muscle can contract. The cells that make up our brains have to have a different structure that would not make them work as muscle cells, but make them good at sending signals. Fat cells can not contract or send nerve impulses, but they are good at storing energy.

There are many “jobs” to do in a human body and many different cell types are needed. A good way to think about this is to consider why many different kinds of vehicles are needed. Big trucks are great for transporting things, but they would lose a race. Fire engines are great at pumping water, but they can’t fly or float. Each of these vehicles has a specific structure that makes it very good at a specific job, but bad at other jobs.

Some living things are made of only one cell that does all the jobs. Take a look at the organelles in one cell and think about how it does the job of an entire system in a person. For example, how does a cell move around without muscles? (Hint: there are different ways.)

Cells are so small that they don’t need systems for moving oxygen, carbon dioxide and many other things. Things just move by a process called diffusion.

If you are interested in how cells work, you may want to study cell biology.