All living beings are made up of cells. Some of them are made up of only one cell and others have many cells. The adult human body is made up of about 60-90 trillion cells. WOW, that's a lot of cells!|
Sometimes people think of cells as a balloon filled with fluid. But a balloon does not let things move in and out like the membrane of a cell. It is important for cells to be able to move materials in and out of the cell. Cells are amazing. They are all made of similar building blocks, but they do many different things depending on how they are programmed.
Some cells carry oxygen to parts of our body. Other cells defend against invading bacteria and viruses. There are cells that transmit signals through out the body like the signals from your eyes to your brain while reading this article.
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