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This chapter provides a brief review of the history of cell discovery and the development of the cell theory. Differences between prokaryotic and eukaryotic cells are mentioned, and observations on cell structure and communication follow. Descriptions are provided for the plasma membrane, nucleus, endoplasmic reticulum, ribosomes, dictyosomes, plastids, mitochondria, microbodies, vacuoles, and the cytoskeleton. The chapter next discusses the cell cycle, including interphase as well as mitosis and cytokinesis, and concludes with a brief comparison of plant and animal cells.

Some Learning Goals

Trace the development of modern cell theory and show how early researchers have led us to our current understanding. Explain the unique structure of plant cells and how communication between and within cells occurs. Know the following cell structures and organelles and indicate the function of each: plasma membrane, nucleus, endo plasmic reticulum, ribosomes, dictyosomes, plastids, mitochondria, microbodies, vacuoles, and cytoskeleton. Describe how information contained in the nucleus relates to other parts of the cell.

Understand the cell cycle and the events that take place in each phase of mitosis.

ll living organisms, from aardvarks to zinnias, are

A composed of cells, and all living organisms, including each of us, also begin life as a single cell. This single cell divides repeatedly until it develops into an organism often consisting of billions of cells. During the first few hours of an organism's development, the cells all look alike, but changes soon take place, not only in the appearance of the cells but also in their function. Some modifications, for example, equip cells to transport food and water, while other cells become modified for secretion of various fluids such as resin or nectar, and still others give strength to tissues such as wood. Some cells may live and function for many years; others mature and degenerate in just a few days. Even as you read this, millions of new cells are being produced in your body. Some cells add to your total body mass (if you have not yet stopped growing), but most replace the millions of older cells that are destroyed every second you remain alive. The variety and form of cells seem almost infinite, but certain features are shared by most of them. A discussion of these features forms the body of this chapter.

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