1. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. MICHAEL D. JOHNSON STRUCTURE AND FUNCTION OF CELLS CHAPTER 3 STRUCTURE AND FUNCTION OF CELLS Part A PowerPoint ® Lecture Slide Presentation by Robert J. Sullivan, Marist College Human Biology Concepts and Current Issues Second Edition

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Eukaryotes have: plasma membrane nucleus: information center cytoplasm: fluid within membrane organelles: structures with specialized functions Prokaryotes have no nucleus or true organelles Cells Are Classified by Internal Organization

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Muscle cells: contain numerous organelles providing energy needed for muscle contraction Nerve cells: are long and thin to carry impulses over distance Small size is efficient Cell Structure Reflects Cell Function

4. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. The Plasma Membrane Figure 3.4

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Lipid bilayer Phospholipids: polar head and nonpolar tail Cholesterol: makes membrane a bit more rigid Proteins: provide means of transportation through membrane Carbohydrates: recognition patterns for cells and organisms Structural Features of the Plasma Membrane

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Diffusion: Passive Transport Through Membrane Passive transport: no energy required Diffusion: movement from area of high concentration to low Figure 3.5

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Osmosis: Diffusion of Water Osmosis: net diffusion of water across a semi-permeable membrane Figure 3.6

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Passive transport is powered by the concentration gradient. In the cell it occurs as: diffusion through lipid layer diffusion through protein channels facilitated transport: transport or carrier proteins in membrane assist moving molecules across the membrane, down the concentration gradient, without expending energy Three Forms of Passive Transport

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Active Transport Active transport requires energy to move substances from area of lower concentration to area of higher concentration. Figure 3.8

10. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Endocytosis and Exocytosis Move Materials in Bulk Endocytosis moves material into cell Exocytosis moves material out of cell Figure 3.9

11. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Receptor Proteins in Active Transport Receptor proteins: span membrane Receptor site: binds specific molecule Figure 3.10

12. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Active Transport: The Sodium/Potassium Pump Sodium/potassium pump expels unwanted ions, keeps needed ones, maintains cell volume ATP used to expel three sodium ions for every two potassium ions brought into the cell Increase cell volume = increase water in cytoplasm by decreasing the pump and allowing more sodium inside cell Decrease cell volume = less water in cytoplasm by increasing the pump and expelling more sodium ions

13. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Tonicity Figure 3.12

14. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Isotonic: extracellular and intracellular ionic concentration equal Hypotonic: extracellular ionic concentration less than intracellular Hypertonic: extracellular ionic concentration more than intracellular Variations in Tonicity

15. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Internal Structures of an Animal Cell Figure 3.13