|MadSci Network: Cell Biology|
Your question is a good one, and it has been studied by scientists who wondered at exactly the same thing as you! Iím going to try to answer it in a way that isnít too hard for a kid to understand.
The "hairs" on a Paramecium are called "cilia", a word that sounds like "sillier" without the r on the end. Thatís the plural. If itís just one, we say "cilium." Whatís really cool is that inside each cilium is a bundle of even tinier "hairs", made of chains of a very special cell protein called "tubulin". A whole lot of single tubulin molecules stick together to make a hollow tube (called a "microtubule"), and each cilium has a bundle of these tubes inside. Microtubules are VERY tiny tubes, only about 20 millionths of one millimeter across! You need an electron microscope to see them unless you put special chemical labels on them to make them glow. Then you can see them with a special kind of light microscope that helps you see things that glow in the dark called a fluorescence microscope.
Each tiny tube has some special stuff stuck to its outside that can grab onto two of the tubes at the same time. This is called "dynein" (sounds like "DIE-neen") and itís what is known as a "motor protein". Itís a special molecule that can bend while itís holding two tubes and then let go and grab a different spot on one of the tubes really fast, like when you go hand over hand on a hanging ladder on the playground (only much, much faster). The energy comes from a special chemical fuel called ATP. The effect of lots of these little movements added up together is to make the whole cilium bend. By beating back and forth in time with each other, the cilia on the outside of the Paramecium cause it to swim around.
Whatís really cool is that the same building blocks are used in our bodies as in the Paramecium. We have cilia in the lining of the "air pipes" that connect our mouth to our lungs. The cilia beat constantly and help clean out dust and other stuff that we breathe all the time and donít even know about. When you look at them in the electron microscope, they have the same shape, theyíre made of the same building blocks, and they work the same way as in the Paramecium. And whatís more, the same kind of tubes and motors are used in all the cells in our bodies to move things around inside them. Sometimes nature sticks to a good thing and uses it over and over to solve the same kind of problem.
I hope this answers your question.
Try the links in the MadSci Library for more information on Cell Biology.