A Tour of the Eukaryotic Cell


Introduction to Cells

Close your eyes and picture a brick wall. What is the basic building block of that wall? A single brick, of course. Like a brick wall, your body is composed of basic building blocks, and the building blocks of your body are cells.

Your body has many kinds of cells, each specialized for a specific purpose. Just as a home is made from a variety of building materials, the human body is constructed from many cell types. For example, epithelial cells protect the surface of the body and cover the organs and body cavities within. Bone cells help to support and protect the body. The cells of the immune system fight invading bacteria. Additionally, blood and blood cells carry nutrients and oxygen throughout the body while removing carbon dioxide. Each of these cell types plays a vital role in the growth, development, and day-to-day maintenance of the body. In spite of their enormous variety, however, cells from all organisms—even ones as diverse as bacteria, onion, and human—share certain fundamental characteristics.

Every living organism is made up of cells which are the basic structural and functional unit of all known living organisms. Cells are the smallest units of life. Organisms can be classified as either unicellular or multi-cellular. Unicellular organisms consist of a single cell and include bacteria. Multicellular organisms include plants and animals. Specifically, in multicellular organisms, there are various types of cells, and it is the interactions between these cells that allow organismal functions to occur. The cell, first discovered in 1665 by Robert Hooke, set the foundation for the development of the cell theory, that states that vital functions of an organism occur within cells and that all cells contain the hereditary information.



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