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Chapter 7

Chapter 7. A View of the Cell. 7.1 History of Cell Theory . Before microscopes were invented, people believed that diseases were caused by curses or supernatural spirits. Anton van Leeuwenhoek developed the first microscope. Invention of microscope allowed scientists to study the cell.

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Chapter 7

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  1. Chapter 7 A View of the Cell

  2. 7.1 History of Cell Theory • Before microscopes were invented, people believed that diseases were caused by curses or supernatural spirits. • Anton van Leeuwenhoek developed the first microscope. • Invention of microscope allowed scientists to study the cell. • Cell = basic units of living organisms

  3. 7.1 Cell Theory • Robert Hooke = first person to develop the idea of cells. • Many scientists took Hooke’s idea and further developed it. • These scientists ideas are summarized in the cell theory.

  4. 7.1 Cell Theory • 1. All organisms are composed of one or more cells • Organisms can be single celled or multicellular • 2. The cell is the basic unit of structures and organization of organisms • Organisms can be complex but they are still made up of tiny cells • 3. All cells come from preexisting cells • Cells divide to form other cells

  5. 7.1 Microscopes • Compound Ligh Microscope • Uses a beam of light that shines up through the specimen • Can magnify an image up to about1500 times its actual size • Electron Microscope • Uses beam of electrons instead of light • Can magnify an image up to 50000 times its actual size • Two types: • Scanning electron microscope • Transmission electron microscope

  6. 7.1 Two Basic Cell Types • All cells contain small, specialized structures called organelles. • Cells are divided into two groups: those that contain membrane bound organelles and those that do. • Prokaryotes – unicellular (mostly), no membrane bound organelles • Eukaryotes – multicellular (mostly), membrane bound organelles • Contains nucleus = brain or control center of the cell

  7. 7.2 The Plasma Membrane • Plasma Membrane = flexible boundary between the cell and its environment • Allows a steady supply of nutrients to enter and exit the cell • Maintains homeostatsis within the cell • How does the plasma membrane maintain homeostasis? • Selective permeability – allows some molecules to pass through while keeping others out.

  8. 7.2 Plasma Membrane • Structure: • Phospholipidbilayer – two layers of phospholipids back – to – back • Phospholipids = glycerol backbone, two fatty acid chains, and a phosphate group • Phosphate group – polar, allows the cell to live in the watery environment • Two fatty acid chains – nonpolar, sandwhiched between two phosphate groups so doesn’t have to come in contract with watery environment • Fluid mosaic model – model of the plasma membrane

  9. 7.2 Plasma Membrane • Cholesterol = helps stabilize the phospholipids by preventing their fatty acid tails from sticking together. • Transport proteins = move needed substances or waste materials through the membrane. • Other proteins and carbohydrates = help cells to identify chemical signals

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