CHAPTER 7 A TOUR OF THE CELL

CHAPTER 7 A TOUR OF THE CELL - CHAPTER 7 A TOUR OF THE CELL...

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CHAPTER 7 A TOUR OF THE CELL All organisms are made of cells, the organism's basic unit of structure and function. The cell as a microcosm can be used to illustrate four themes integral to the text and course: 1. Theme of emergent properties. Life at the cellular level arises from interactions among cellular components. 2. Correlation of structure and function. Ordered cellular processes (e.g., protein synthesis, respiration, photosynthesis, cell-cell recognition, cellular movement, membrane production and secretion) are based upon ordered structures. 3. Interaction of organisms within their environment. Cells are excitable responding to environmental stimuli. In addition, cells are open systems that exchange materials and energy with their environment. 4. Unifying theme of evolution. Evolutionary adaptations are the basis for the correlation between structure and function. I. How We Study Cells A. Microscopes provide windows to the world of the cell The microscope's invention and improvement in the seventeenth century led to the discovery and study of cells. II. A Panoramic View of the Cell A. Prokaryotic and eukaryotic cells differ in size and complexity Living organisms are made of either prokaryotic or eukaryotic cells-two major kinds of cells, which can be distinguished by structural organization. Prokaryotic Eukaryotic (pro = before; karyon = kernel) (Eu = true; karyon = kernel) Found only in bacteria and Found in the Kingdoms Protisa, archaebacteria Fungi, Plantae, and Animalia No true nucleus; lacks nuclear True nucleus; bounded by nuclear envelope envelope Genetic material in nucleoid region Genetic material within nucleus No membrane-bound organelles Contains cytoplasm with cytosol membrane-bound organelles
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Cytoplasm = Entire region between the nucleus and cell membrane Cytosol = Semi-fluid medium found in the cytoplasm 1. Cell size Size ranges of cells: Cell Type Diameter Mycoplasmas 0.1 - 1.0 m Most bacteria 1.0 - 10.0 m Most eukaryotic cells 10.0 - 100.0 m Range of cell size is limited by metabolic requirements. The lower limits are probably determined by the smallest size with enough: - DNA to program metabolism. - ribosomes, enzymes and cellular componentts to sustain life and reproduce. The upper limits of size are imposed by the surface area to volume ratio. As a cell increases in size, its volume grows proportionately more than its surface area. - The surface area of the plasma membrane mmust be large enough for the
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CHAPTER 7 A TOUR OF THE CELL - CHAPTER 7 A TOUR OF THE CELL...

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