Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 5 The Working Cell

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Cool “Fires” Attract Mates and Meals Fireflies use light to send signals to potential mates –Instead of using chemical signals like most other insects

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The light comes from a set of chemical reactions –That occur in light-producing organs at the rear of the insect

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Females of some species –Produce a light pattern that attracts males of other species, which are then eaten by the female

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ENERGY AND THE CELL 5.1 Energy is the capacity to perform work All organisms require energy –Which is defined as the capacity to do work

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Kinetic energy is the energy of motion Potential energy is stored energy –And can be converted to kinetic energy Figure 5.1A–C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.2 Two laws govern energy transformations Thermodynamics –Is the study of energy transformations

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The First Law of Thermodynamics According to the first law of thermodynamics –Energy can be changed from one form to another –Energy cannot be created or destroyed Figure 5.2A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The Second Law of Thermodynamics The second law of thermodynamics –States that energy transformations increase disorder or entropy, and some energy is lost as heat Figure 5.2B Heat Chemical reactions ATP Glucose + Oxygen water Carbon dioxide + Energy for cellular work

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.3 Chemical reactions either store or release energy Endergonic reactions –Absorb energy and yield products rich in potential energy Figure 5.3A Potential energy of molecules Reactants Energy required Products Amount of energy required

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Exergonic reactions –Release energy and yield products that contain less potential energy than their reactants Figure 5.3B Reactants Energy released Products Amount of energy released Potential energy of molecules

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Cells carry out thousands of chemical reactions –The sum of which constitutes cellular metabolism Energy coupling –Uses exergonic reactions to fuel endergonic reactions

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.4 ATP shuttles chemical energy and drives cellular work ATP powers nearly all forms of cellular work

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The energy in an ATP molecule –Lies in the bonds between its phosphate groups Phosphate groups ATP Energy PPP P PP Hydrolysis Adenine Ribose H2OH2O Adenosine diphosphate Adenosine Triphosphate + + ADP Figure 5.4A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ATP drives endergonic reactions by phosphorylation –Transferring a phosphate group to make molecules more reactive Figure 5.4B ATP Chemical work Mechanical work Transport work P P P P P P P Molecule formedProtein moved Solute transported ADP + Product Reactants Motor protein Membrane protein Solute +

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ATP ADP + P Energy for endergonic reactions Energy from exergonic reactions Phosphorylation Hydrolysis Cellular work can be sustained –Because ATP is a renewable resource that cells regenerate Figure 5.4C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings HOW ENZYMES FUNCTION 5.5 Enzymes speed up the cell’s chemical reactions by lowering energy barriers

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings For a chemical reaction to begin –Reactants must absorb some energy, called the energy of activation Figure 5.5A E A barrier Reactants Products 12 Enzyme

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A protein catalyst called an enzyme –Can decrease the energy of activation needed to begin a reaction Figure 5.5B Reactants E A without enzyme E A with enzyme Net change in energy Products Energy Progress of the reaction

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.6 A specific enzyme catalyzes each cellular reaction Enzymes have unique three-dimensional shapes –That determine which chemical reactions occur in a cell

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 5.6 Enzyme (sucrase) Glucose Fructose Active site Substrate (sucrose) H2OH2O 1 Enzyme available with empty active site 2 Substrate binds to enzyme with induced fit 4 Products are released 3 Substrate is converted to products The catalytic cycle of an enzyme

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.7 The cellular environment affects enzyme activity Temperature, salt concentration, and pH influence enzyme activity Some enzymes require nonprotein cofactors –Such as metal ions or organic molecules called coenzymes

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.8 Enzyme inhibitors block enzyme action Inhibitors interfere with an enzyme’s activity

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A competitive inhibitor –Takes the place of a substrate in the active site A noncompetitive inhibitor –Alters an enzyme’s function by changing its shape Figure 5.8 Substrate Enzyme Active site Normal binding of substrate Enzyme inhibition Noncompetitive inhibitor Competitive inhibitor

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 5.9 Many poisons, pesticides, and drugs are enzyme inhibitors

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings MEMBRANE STRUCTURE AND FUNCTION 5.10 Membranes organize the chemical activities of cells Membranes –Provide structural order for metabolism

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The plasma membrane of the cell is selectively permeable –Controlling the flow of substances into or out of the cell Figure 5.10 Cytoplasm Outside of cell TEM 200,000 

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.11 Membrane phospholipids form a bilayer Phospholipids –Have a hydrophilic head and two hydrophobic tails –Are the main structural components of membranes Figure 5.11A CH 2 CH 3 CH 2 CH CH 2 CH 3 CH 2 CH 3 N + O O O–O– P O CH 2 CH CH 2 C O C O O O Phosphate group Symbol Hydrophilic head Hydrophobic tails

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Phospholipids form a two-layer sheet –Called a phospholipid bilayer, with the heads facing outward and the tails facing inward Figure 5.11B Water Hydrophilic heads Hydrophobic tails

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.12 The membrane is a fluid mosaic of phospholipids and proteins A membrane is a fluid mosaic –With proteins and other molecules embedded in a phospholipid bilayer Figure 5.12 Fibers of the extracellular matrix Carbohydrate (of glycoprotein) Glycoprotein Microfilaments of cytoskeleton Phospholipid Cholesterol Proteins Plasma membrane Glycolipid Cytoplasm

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.13 Proteins make the membrane a mosaic of function Many membrane proteins –Function as enzymes Figure 5.13A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Other membrane proteins –Function as receptors for chemical messages from other cells Figure 5.13B Messenger molecule Receptor Activated molecule

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Membrane proteins also function in transport –Moving substances across the membrane Figure 5.13C ATP

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.14 Passive transport is diffusion across a membrane In passive transport, substances diffuse through membranes without work by the cell –Spreading from areas of high concentration to areas of low concentration EquilibriumMembraneMolecules of dye Equilibrium Figure 5.14B Figure 5.14A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Small nonpolar molecules such as O 2 and CO 2 –Diffuse easily across the phospholipid bilayer of a membrane

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.15 Transport proteins may facilitate diffusion across membranes Many kinds of molecules –Do not diffuse freely across membranes For these molecules, transport proteins –Provide passage across membranes through a process called facilitated diffusion Figure 5.15 Solute molecule Transport protein

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.16 Osmosis is the diffusion of water across a membrane In osmosis –Water travels from a solution of lower solute concentration to one of higher solute concentration Figure 5.16 Lower concentration of solute Higher concentration of solute Equal concentration of solute H2OH2O Solute molecule Selectively permeable membrane Water molecule Solute molecule with cluster of water molecules Net flow of water

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.17 Water balance between cells and their surroundings is crucial to organisms Osmosis causes cells to shrink in hypertonic solutions –And swell in hypotonic solutions In isotonic solutions –Animal cells are normal, but plant cells are limp Figure 5.17 Plant cell H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O Plasma membrane (1) Normal (2) Lysed (3) Shriveled (4) Flaccid (5) Turgid (6) Shriveled (plasmolyzed) Isotonic solution Hypotonic solution Hypertonic solution Animal cell

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The control of water balance –Is called osmoregulation

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings P P P Protein changes shape Phosphate detaches ATP ADP Solute Transport protein Solute binding1Phosphorylation2 Transport 3 Protein reversion Cells expend energy for active transport Transport proteins can move solutes against a concentration gradient –Through active transport, which requires ATP Figure 5.18

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Fluid outside cell Cytoplasm Protein Vesicle 5.19 Exocytosis and endocytosis transport large molecules To move large molecules or particles through a membrane –A vesicle may fuse with the membrane and expel its contents (exocytosis) Figure 5.19A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Membranes may fold inward –Enclosing material from the outside (endocytosis) Figure 5.19B Vesicle forming

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Endocytosis can occur in three ways –Phagocytosis –Pinocytosis –Receptor-mediated endocytosis Pseudopodium of amoeba Food being ingested Phagocytosis Pinocytosis Receptor-mediated endocytosis Material bound to receptor proteins PIT Cytoplasm Plasma membrane TEM 54,000  TEM 96,500  LM 230  Figure 5.19C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 5.20 Faulty membranes can overload the blood with cholesterol Harmful levels of cholesterol –Can accumulate in the blood if membranes lack cholesterol receptors LDL particle Protein Phospholipid outer layer Cytoplasm Receptor protein Plasma membrane Vesicle Cholesterol Figure 5.20

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5.21 Chloroplasts and mitochondria make energy available for cellular work Enzymes are central to the processes that make energy available to the cell

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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