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Cells All living things are made of cells. A single cell cannot be seen without the help of a microscope. The microscope allows us to look at a magnified, or larger, view of a microscopic object. All cells have a protective covering called a cell membrane. Everything inside the cell floats in a jelly-like material called cytoplasm. All cells have a nucleus, which controls growth and reproduction. Plant cells also have a crunchy cell wall and chloroplasts. The chloroplasts hold the chlorophyll. Chlorophyll is the green chemical that allows a plant cell to make its own food. The process of making food is called photosynthesis. Tiny Kingdoms Not all living things are plants or animals. Moneran are simple single-celled living things. Bacteria and Algae are Moneran. Protists are complex single-celled living things. Protists sometimes have whip-like parts called flagella. Some Protists have tiny hair-like parts, called cilia. Another kingdom of living things is Fungi. Mushrooms and mold are fungi. They absorb food from living or dead things. They do not make their own food. The Good, the Bad, and the Ugly Some microscopic life is helpful, such as the yeast used to make bread. Some microscopic life can make us sick. We can kill some bacteria outside the body with antiseptics. We can kill some germs in our body with antibiotics. Since bacteria are alive, we can cure a bacterial infection by killing the bacteria. Another microscopic thing that can make us sick is a virus. A virus is not alive, but can get inside the nucleus of our cells and make us sick. Sometimes you can take a shot, called a vaccination, to keep you from catching a viral infection. Sometimes our blood makes special chemicals called antibodies, which attack germs and keep us from getting an illness more than one time. Some diseases are easy to prevent. Others are not. One deadly disease we all need to know about is AIDS, which is caused by the HIV virus. Since there is no cure yet, it is important that we know how to be safe. This means to be very careful in any situations where we would come in contact with another person’s body fluids.
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