Cells

Introduction

Cell is the basic unit of life. All living organisms are composed of cells, and all cells arise from other cells. These simple and powerful statements form the basis of the cell theory. English physicist and microscopist Robert Hooke (1635–1702) first described cells in 1665. The first cell that he observed was the cork cell. Marcello Malpighi (1628–1694), and Hooke's colleague, Nehemiah Grew (1641–1712), made detailed studies of plant cells and established the presence of cellular structures throughout the plant body. The presence of cells in animal tissue was demonstrated later than in plants because the thin sections needed for viewing under the microscope are more difficult to prepare for animal tissues. The prevalent view of Hooke's contemporaries was that animals were composed of various types of fibers, properties of which accounted for the differences among tissues. The invention of the microscope allowed the first view of cells. In 1676 the Dutch microscopist Antony van Leeuwenhoek (1632–1723), Father of microscopy, published his observations of single-cell organisms. Leeuwenhoek made numerous and detailed observations on his microorganisms, but more than one hundred years passed before a connection was made between the obviously cellular structure of these creatures and the existence of cells in animals or plants.( Harris, Henry,1999).Cells are extremely small, it can only be seen properly when magnified and viewed through the lenses of a microscope which mostly have few objective lenses, for instance x4(low power), x10 (medium power) and x40(high power). The image of the specimen is magnified again by an eyepiece by a factor of 10. The shapes, sizes, and the structure of the cells of plants and animals vary from one another. Variety reflects the distinct functions for which cells are adapted.(C J Clegg and D G Mackean,2000.) Cells are composed of biological molecules in which it is also known as cellular components. Biological...