Chapter 4 Cell Structure and Function

Chapter 4 Cell Structure and Function - Chapter 4 Cell...

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Chapter 4 Cell Structure and Function: An Overview I. Pastures of the Seas A. Vast populations of single-celled organisms (phytoplankton) carry on photosynthesis. B. These cells also respond to changes in their oceanic environment. II. Generalized Picture of the Cell A. Emergence of the Cell Theory 1. In the early seventeenth century, Galileo Galilei first used a microscope to observe a biological specimen (an insect eye). 2. By mid-seventeenth century, Robert Hooke first used the term “cell” to refer to the compartments in a slice of cork. 3. Anton van Leeuwenhoek observed a bacterium with the use of microscope. 4. In the 1820s, Robert Brown found a structure in every plant cell and called it the nucleus. 5. In 1839, Theodor Schwann noted cells in animal tissues. 6. Matthias Schleiden concluded that all plant tissues are composed of cells. 7. Schwann first stated two aspects of the cell theory: All life is composed of cells, and the cell is the basic unit of life. 8. A decade later Rudolf Virchow added another part to the cell theory: All cells arise from preexisting cells. B. Basic Aspects of Cell Structure and Function 1. All cells have a nucleus (or nucleoid), cytoplasm, and a plasma membrane. 2. A plasma membrane separates each cell from the environment, permits the flow of molecules across the membrane, and contains receptors that can affect the cell’s activities. 3. A nucleus is membrane bound and contains DNA. A bacterial cell’s DNA is found in the nucleoid region that is not membrane bound. 4. The cytoplasm contains membrane systems, particles, filaments (the cytoskeleton), and a semifluid substance. C. Cell Size and Shape 1. Most cells are too small to be seen without a microscope. 2. Light microscopes can explore details of 0.2 micrometer, and electron microscopes can observe much smaller details. 3. The small size of cells permits efficient diffusion across the plasma membrane and within the cell. 4. As the surface area of a cell increases to the square of the diameter, the volume increases to the cube of the diameter. III. Prokaryotic Cells—The Bacteria
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A. Bacteria are some of the smallest and simplest cells. 1. A somewhat rigid cell wall supports the cell and surrounds the plasma membrane, which regulates transport into and out of the cell. 2. Ribosomes, protein assembly sites, are dispersed throughout the cytoplasm.
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Chapter 4 Cell Structure and Function - Chapter 4 Cell...

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