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BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence.

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Presentation on theme: "BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence."— Presentation transcript:

1 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

2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Structure of the Plasma Membrane Fibers of the extracellular matrix Figure 5.12 Glycoprotein Carbohydrate (of glycoprotein) Microfilaments of the cytoskeleton Phospholipid Cholesterol Proteins CYTOPLASM Glycolipid

3 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 Membrane phospholipids form a bilayer Head Symbol Tails Figure 5.11A

4 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

5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The cell membrane is about 10 nm thick discernable only faintly with a transmission electron microscope.nmtransmission electron microscope The membrane is specialized in that it contains specific proteins and lipid components that enable it to perform its unique roles for the cell.

6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Phospholipid molecules form a flexible bilayer –Phospholipid molecules in the cell membrane are "fluid," in the sense that they are free to diffuse and exhibit rapid lateral diffusion. Lipid rafts and caveolae are examples of cholesterol-enriched microdomains in the cell membraneLipid raftscaveolae –The plasma membrane lipids consist of 1/3 cholesterol and 2/3 phospholipids (65-80%) and sphingolipids (20-35%). The outer leaflet contains 5% glycolipids.cholesterolphospholipidssphingolipidsglycolipids –Cholesterol is embedded in the plasma membrane –Phospholipids flow at a rate of 2 micrometers/second The membrane is a fluid mosaic made of phospholipids and proteins

7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Membrane proteins can span the lipid bilayer while others are peripheral.

8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Membranes organize the chemical reactions making up metabolism MEMBRANE FUNCTION Cytoplasm   Figure 5.10

9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings T he membrane : Sorts what goes in and out of the cell. Membranes are selectively permeable. Anchors of the cytoskeleton to provide shape to the cellcytoskeleton Attaches to the extracellular matrix to help group cells together in the formation of tissuesextracellular matrixtissues Transports particles by way of ion pumps, ion channels, and carrier proteinsion pumpsion channelscarrier proteins Contains receptors that allow chemical messages to pass between cells and systemsreceptors Participates in enzyme activity important in such things as metabolism and immunityenzyme metabolismimmunity

10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Membranes are selectively permeable –They control the flow of substances into and out of a cell

11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some membrane proteins form cell junctions Others transport substances across the membrane The Membrane Proteins: allow chemical messages to pass between cells and systems Transport Figure 5.13

12 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

13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Passive and Active Transport Across the Membrane A.Passive Transport does not require energy 1. Simple diffusion 2. Osmosis 3. Diffusion by transport proteins (carrier proteins, channel proteins). B. Active Transport requires energy

14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In simple diffusion, substances diffuse through membranes without work by the cell –They spread from areas of high concentration to areas of lower concentration –Solutes move with the concentration gradient –Solute specific Passive transport is diffusion across a membrane without expending energy EQUILIBRIUM Molecule of dye Figure 5.14A & B Membrane EQUILIBRIUM

15 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 Not solute specific 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

16 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 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

17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Small nonpolar molecules diffuse freely through the phospholipid bilayer but: Many other kinds of molecules pass through selective protein pores (carrier proteins) by facilitated diffusion Transport proteins facilitate diffusion across membranes as passive transport. Figure 5.17 Solute molecule Transport protein

18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Facilitated Diffusion

19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Channel Proteins move ions passively through the membrane.

20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

21 Transport proteins can move solutes across a membrane against a concentration gradient –This is called active transport –Active transport requires ATP Cells expend energy for active transport

22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Active transport in two solutes across a membrane Figure 5.18 Transport protein 1 FLUID OUTSIDE CELL First solute First solute, inside cell, binds to protein Phosphorylated transport protein 2 ATP transfers phosphate to protein 3 Protein releases solute outside cell 4 Second solute binds to protein Second solute 5 Phosphate detaches from protein 6 Protein releases second solute into cell

23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

24 Direction of transport Uniports Co-transports-symports and antiports

25 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---active transport Figure 5.19A FLUID OUTSIDE CELL CYTOPLASM

26 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –or the membrane may fold inward, trapping material from the outside (endocytosis) Figure 5.19B

27 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

28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Harmful levels of cholesterol can accumulate in the blood if membranes lack cholesterol receptors 5.20 Connection: Faulty membranes can overload the blood with cholesterol Figure 5.20 LDL PARTICLE Phospholipid outer layer Protein Cholesterol Plasma membrane CYTOPLASM Receptor protein Vesicle

29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Enzymes and membranes are central to the processes that make energy available to the cell Chloroplasts carry out photosynthesis, using solar energy to produce glucose and oxygen from carbon dioxide and water Mitochondria consume oxygen in cellular respiration, using the energy stored in glucose to make ATP 5.21 Chloroplasts and mitochondria make energy available for cellular work

30 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nearly all the chemical energy that organisms use comes ultimately from sunlight Chemicals recycle among living organisms and their environment Figure 5.21 Sunlight energy Chloroplasts, site of photosynthesis CO 2 + H 2 O Glucose + O 2 Mitochondria sites of cellular respiration (for cellular work) Heat energy


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