BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 5 The Working Cell Modules 5.10 – 5.21
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell membranes controls entry and exit of materials into the cell CELL MEMBRANE STRUCTURE AND FUNCTION Cytoplasm Figure 5.10 Membranes are selectively permeable or semipermeable (some substances can pass throught it, while others cannot).
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The cell membrane has 2 major components: 1. A double layer of phospholipids (lipid bilayer) 2. Protein molecules that serve as channels, pumps or receptors for communication. Your teacher will draw this on the board for you to copy.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Phospholipids are the main structural components of membranes They each have a hydrophilic head and two hydrophobic tails 5.11 Membrane phospholipids form a bilayer Head Symbol Tails Figure 5.11A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In water, phospholipids form a stable bilayer Figure 5.11B Hydrophilic heads Hydrophobic tails Water –The heads face outward and the tails face inward
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The plasma membrane of an animal cell Fibers of the extracellular matrix Figure 5.12 Glycoprotein Carbohydrate (of glycoprotein) Microfilaments of the cytoskeleton Phospholipid Cholesterol Proteins CYTOPLASM Glycolipid
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Proteins that serve as channels Others transport substances across the membrane 5.13 Proteins make the membrane a mosaic of function Transport Figure 5.13
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell membrane structure online.com/objects/index_tj.asp?obj id=AP1101
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings STOP for demonstration
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Your cells can move some substances across their membranes using NO ENERGY!
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Background Information on Diffusion - Diffusion is a process where molecules move from a region of higher concentration to a region of lower concentration. - The difference in concentration on either side of a membrane is known as a concentration gradient.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Background Information on Diffusion - Diffusion of water molecules across a membrane is known as osmosis. - Diffusion will occur until an equilibrium is reached. (some will move each direction in equal amounts)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In passive transport, substances diffuse through membranes without work by the cell –They spread from areas of high concentration to areas of lower concentration 5.14 Passive transport is diffusion across a membrane EQUILIBRIUM Molecule of dye Figure 5.14A & B Membrane EQUILIBRIUM
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Many membrane proteins are enzymes Figure 5.13 Some proteins function as receptors for chemical messages from other cells –The binding of a messenger to a receptor may trigger signal transduction Enzyme activitySignal transduction Messenger molecule Receptor Activated molecule
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Transport Across the Cell Membrane The cell uses 2 types of transport: 1. Passive transport - Passive transport requires NO ENERGY use by the cell. Substances move along a concentration gradient.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings a. Molecules may be moved through a process called simple diffusion. 1. Passive transport continued… - Examples:Water, oxygen, carbon dioxide, lipid soluble molecules
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1. Passive transport continued… b. Facilitated diffusion - Uses carrier proteins to transport molecules that are not lipid soluble - Examples: glucose, some ions – sodium, potassium
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings ogy1111/animations/transport1.html Link to illustrate passive transport
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2. Active Transport - This transport requires the cell to USE ENERGY - Examples: large compounds or electrically charged particles OR when molecules are moved against the concentration gradient.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2. Active Transport 2 types of Active Transport a.Protein Pumps – carry ions across the membrane neuron animation neuron animation b. Bulk Transport - This is where large amounts of molecules are carried across. There are 3 types of this.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1. Endocytosis – cell membrane brings materials into the cell by infoldings of the membrane which can form vacuoles. 2. Active Transport b. Bulk Transport 2 Forms:Phagocytosis – ameba undissolved materialsameba Pinocytosis – dissolved materials Ex: Ameba eating food
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –or the membrane may fold inward, trapping material from the outside (endocytosis) Figure 5.19B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Three kinds of endocytosis Figure 5.19C Pseudopod of amoeba Food being ingested Plasma membrane Material bound to receptor proteins PIT Cytoplasm
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2. Active Transport b. Large quantity Transport 2. Exocytosis – removes material from the cell through outpinchings of the cell membrane. Ex: wastes 3. Contractile Vacuole - Used for removing excess water from a cell. Ex: a freshwater paramecium contractile vacuole videocontractile vacuole video
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings To move large molecules or particles through a membrane –a vesicle may fuse with the membrane and expel its contents (exocytosis) 5.19 Exocytosis and endocytosis transport large molecules Figure 5.19A FLUID OUTSIDE CELL CYTOPLASM
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings ogy1111/animations/transport1.html Link to illustrate active transport
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings What will happen to a plant or animal cell when placed in fresh or salt water?
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Background Information Hypertonic – Solution that has a higher concentration of Solute than a surrounding solution Hypotonic – Solution that has a lower concentration of solute than a surrounding Solution Isotonic – Two solutions have the same solute concentrations
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings FRESH WATER Animal CellPlant Cell - water is more highly concentrated outside the cell - water will enter the cell 100% H 2 0 Cell 85% H 2 0 SAME, but plant w/cell wall
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Red blood cell will explode. (called CYTOLYSIS) Plant Cell will NOT explode because the cell wall prohibits it. (becomes TURGID)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings SALT WATER Animal cellPlant Cell - water is more highly concentrated inside the cell - water will exit the cell 80% H % salt Cell 85% H 2 0 SAME, but plant w/cell wall
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings -Animal Cell will lose water and shrink (becomes CRENATE) - Plant cell will lose water. - The cell membrane will pull away from the cell wall – (this is called PLASMOLYSIS.)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings online.com/objects/index_tj.asp?objid=AP11003 osmosis Red blood cell in isotonic environment Red blood cell in hypertonic solution cytolysis and crenation in red blood cells
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentration 5.15 Osmosis is the passive transport of water Hypotonic solution Figure 5.15 Solute molecule HYPOTONIC SOLUTION Hypertonic solution Selectively permeable membrane HYPERTONIC SOLUTION Selectively permeable membrane NET FLOW OF WATER Solute molecule with cluster of water molecules Water molecule
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution –The control of water balance (osmoregulation) is essential for organisms 5.16 Water balance between cells and their surroundings is crucial to organisms ISOTONIC SOLUTION Figure 5.16 HYPOTONIC SOLUTION HYPERTONIC SOLUTION (1) Normal (4) Flaccid (2) Lysing (5) Turgid (3) Shriveled (6) Shriveled ANIMAL CELL PLANT CELL Plasma membrane
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Small nonpolar molecules diffuse freely through the phospholipid bilayer Many other kinds of molecules pass through selective protein pores by facilitated diffusion 5.17 Transport proteins facilitate diffusion across membranes Figure 5.17 Solute molecule Transport protein