1. 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 The Working Cell Chapter 5

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cool "Fires" Attract Mates and Meals Living cells put energy to work by means of enzyme-controlled reactions The firefly's use of light to signal mates results from a set of such reactions – The reactions occur in light-producing organs at the rear of the insect – Females of some species produce a light pattern that attracts males of other species, which the female eats

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.1 Energy is the capacity to perform work Energy is defined as the capacity to do work Work is a force acting on an object that causes the object to move Life depends on the fact that energy can be converted from one form to another

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The two fundamental types of energy Kinetic energy is the energy of movement – e.g. light, heat, electricity, moving objects Potential energy is stored energy that is dependent on an object's location or structure – e.g. chemical energy in bonds, electrical charge in a battery, a rock at the top of a hill – The most important potential energy for living things is the chemical energy stored in molecules

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemical energy is the energy that powers life The objects that move are electrons, which reposition during chemical reactions Potential energy can be converted to kinetic energy

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.2 Two laws govern energy transformations Thermodynamics is the study of energy transformations The First Law of Thermodynamics – Energy can be changed from one form to another but cannot be created or destroyed

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Second Law of Thermodynamics – Energy doesn't tend to stay concentrated in a small space; it tends to flow toward becoming dispersed if it can – Ex. electricity in a battery, power line or lightning, wind from a high pressure weather system, air compressed in a tire, all heated objects, loud sounds, or boulders that are high up on a mountain. – Energy transformations increase disorder, or entropy, and some energy is lost as heat

12. All these different kinds of energy spread out if there's a way they can do so.

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Laws of Thermodynamics Availability and usefulness of energy: The amount of useful energy decreases when energy is converted from one form to another (second law of thermodynamics) Entropy (disorder) increases

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15. LE 5-2b Heat Glucose Oxygen Chemical reactions ATP Energy for cellular work Carbon dioxide Water

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy of Sunlight Living things must gain external energy in order to counteract the increase in their entropy

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.3 Chemical reactions either store or release energy Endergonic reactions (stores energy) – Require an input of energy from the surroundings – Yield products rich in potential energy – Example:

18. LE 5-3a Reactants Products Amount of energy required Potential energy of molecules Energy required

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exergonic reactions – Release energy – Yield products that contain less potential energy than their reactants – Examples: cellular respiration, burning

20. LE 5-3b Energy released Potential energy of molecules Reactants Products Amount of energy released

21. Heat Glucose Oxygen Chemical reactions ATP Energy for cellular work Carbon dioxide Water Cellular respiration An “Exergonic Reaction”

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23. Coupled Reactions Cells carry out thousands of chemical reactions, which constitute cellular metabolism Energy coupling uses energy released from exergonic reactions to drive endergonic reactions

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The exergonic and endergonic parts of coupled reactions often occur at different places within the cell Energy-carrier molecules are used to transfer the energy within cells

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ATP Adenosine triphosphate (ATP) is the most common energy carrying molecule

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.4 ATP shuttles chemical energy and drives cellular work ATP (adenosine triphosphate) powers nearly all forms of cellular work ATP is composed of one adenine, one ribose, and three negatively charged phosphates The energy in an ATP molecule lies in the bonds between its phosphate groups

27. LE 5-4a AdenosineTriphosphate Phosphate group PPP H2OH2O Hydrolysis ATP ADP Ribose Adenine Adenosine diphosphate PPP Energy  High energy bond

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ATP powers cellular work through coupled reactions – The bonds connecting the phosphate groups are broken by hydrolysis, an exergonic reaction – Hydrolysis is coupled to an endergonic reaction through phosphorylation A phosphate group is transferred from ATP to another molecule

29. LE 5-4b ATP Chemical work Mechanical workTransport work P P P P P P P ADP  Reactants Product Molecule formed Protein moved Solute transported Motor protein Membrane protein Solute

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular work can be sustained, because ATP is a renewable resource that cells regenerate – The ATP cycle involves continual phosphorylation and hydrolysis

31. LE 5-4c Energy from exergonic reactions ATP ADP  P Energy for endergonic reactions Hydrolysis Phosphoylation

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Spontaneous Reactions At body temperatures, spontaneous reactions proceed too slowly to sustain life

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Spontaneous Reactions Reaction speed is generally determined by the activation energy required Reactions with low activation energies proceed rapidly at body temperature Reactions with high activation energies (e.g. sugar breakdown) move very slowly at body temperature

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Enzyme molecules (proteins) are employed to catalyze (speed up) chemical reactions in cells

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Catalysts Reduce Activation Energy Catalysts speed up the rate of a chemical reaction without themselves being used up

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.5 Enzymes speed up the cell's chemical reactions by lowering energy barriers HOW ENZYMES FUNCTION Energy of activation= Amount of energy that must be input before an exergonic reaction will proceed (the energy barrier) link: activation energy

38. Reactants Net change in energy E A without enzyme Products Progress of the reaction Energy E A with enzyme

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Link: activation energy animation

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.6 A specific enzyme catalyzes each cellular reaction Each enzyme has a unique three-dimensional shape that determines which chemical reaction it catalyzes – Substrate: a specific reactant that an enzyme acts on – Active site: A pocket on the enzyme surface that the substrate fits into

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Induced fit: The way the active site changes shape to "embrace" the substrate A single enzyme may act on thousands or millions of substrate molecules per second Animation: How Enzymes Work Animation: How Enzymes Work

42. Enzyme available with empty active site Active site Glucose Fructose Products are released Enzyme (sucrase) Substrate (sucrose) H2OH2O Substrate is converted to products Substrate binds to enzyme with induced fit

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Environmental Conditions Some enzymes require helper non protein cofactors molecules to function (e.g. certain B vitamins, Metal ions, organic molecules called coenzymes) Metal ions Vitamin B12

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.7 The cellular environment affects enzyme activity Three-dimensional structure of an enzyme is sensitive to pH, salts, temperature, and presence of coenzymes

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Environmental Conditions Enzyme structure is distorted and function is destroyed when pH is too high or low Salts in an enzyme’s environment can also destroy function by altering structure

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47. Environmental Conditions Temperature also affects enzyme activity Low temperatures slow down molecular movement High temperatures cause enzyme shape to be altered, destroying function

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49. Environmental Conditions Most enzymes function optimally only within a very narrow range of these conditions

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.8 Enzyme inhibitors block enzyme action Inhibitors interfere with an enzyme's activity 1.A competitive inhibitor takes the place of a substrate in the active site 2.A noncompetitive inhibitor alters an enzyme's function by changing its shape

51. LE 5-8 Substrate Enzyme Active site Normal binding of substrate Competitive inhibitor Noncompetitive inhibitor Enzyme inhibition

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3. In feedback inhibition, enzyme activity is blocked by a product of the reaction catalyzed by the enzyme

53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.9 Many poisons, pesticides, and drugs are enzyme inhibitors Cyanide inhibits an enzyme involved with ATP production during cellular respiration Some pesticides irreversibly inhibit an enzyme crucial for insect muscle function Many antibiotics inhibit enzymes essential for disease-causing bacteria Ibuprofen and aspirin inhibit enzymes involved in inducing pain

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.10 Membranes organize the chemical activities of cells Membranes provide structural order for metabolism – Form most of the cell's organelles – Compartmentalize chemical reactions Functions of the plasma membrane ―Isolates the cell’s contents from environment ―Regulates exchange of essential substances ― Communicates with other cells ―Creates attachments within and between other cells ―Regulates biochemical reactions

55. LE 5-10 Outside of cell Cytoplasm

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.11 Membrane phospholipids form a bilayer Phospholipids are the main structural components of membranes – Two nonpolar hydrophobic fatty acid "tails" – One phosphate group attached to the hydrophilic glycerol "head"

57. LE 5-11a Hydrophilic head Phosphate group Symbol Hydrophobic tails

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In membranes, phospholipids form a bilayer – Two-layer sheet – Phospholipid heads facing outward and tails facing inward – Selectively permeable Nonpolar/small lipid-soluble molecules, pass through Polar molecules not soluble in lipids do not pass through

59. LE 5-11b Hydrophilic heads Hydrophobic tails Water

60. 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 mosaic – Proteins and other molecules are embedded in a framework of phospholipids A membrane is fluid – Most protein and phospholipid molecules can move laterally Membrane glycoproteins and glycolipids function in cell identification

61. LE 5-12 Extracellular matrix Glycoprotein Carbohydrate Plasma membrane Microfilaments of cytoskeleton Phospholipid Cholesterol Proteins Cytoplasm Glycolipid

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.13 Proteins make the membrane a mosaic of function Proteins perform most membrane functions – Identification tags – Junctions between adjacent cells – Enzymes – Receptors of chemical messages from other cells (signal transduction) – Transporters of substances across the membrane

63. LE 5-13a Enzyme activity

64. LE 5-13b Messenger molecule Receptor Activated molecule Signal transduction

65. LE 5-13c Transport ATP

66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Membrane Selectivity Animation: Membrane Selectivity

67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.14 Passive transport is diffusion across a membrane Diffusion is the tendency for particles to spread out evenly in an available space – From an area of high concentration to an area of low concentration Passive transport across membranes occurs when a molecule diffuses down a concentration gradient Small nonpolar molecules such as O 2 and CO 2 diffuse easily across the phospholipid bilayer of a membrane

68. LE 5-14a Molecules of dye Membrane Equilibrium

69. LE 5-14b Equilibrium

70. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Diffusion Animation: Diffusion

71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.15 Transport proteins may facilitate diffusion across membranes In facilitated diffusion – Transport proteins that span the membrane bilayer help substances diffuse down a concentration gradient To transport the substance, a transport protein may – Provide a pore for passage – Bind the substance, change shape, and then release the substance

72. LE 5-15 Solute molecule Transport protein

73. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.16 Osmosis is the diffusion of water across a membrane In osmosis water, molecules diffuse across a selectively permeable membrane – From an area of low solute concentration – To an area of high solute concentration – Until the solution is equally concentrated on both sides of the membrane The direction of movement is determined by the difference in total solute concentration – Not by the nature of the solutes Animation: Osmosis Animation: Osmosis

74. LE 5-16 Water molecule Selectively permeable membrane Solute molecule H2OH2O Lower concentration of solute Higher concentration of solute Equal concentration of solute Solute molecule with cluster of water molecules Net flow of water

75. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.17 Water balance between cells and their surroundings is crucial to organisms Osmoregulation is the control of water balance Tonicity is the tendency of a cell to lose or gain water in solution – Isotonic solution: solute concentration is the same in the cell and in the solution No osmosis occurs Animal cell volume remains constant; plant cell becomes flaccid

76. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Hypotonic solution: solute concentration is greater in the cell than in the solution Cell gains water through osmosis Animal cell lyses; plant cell becomes turgid – Hypertonic solution: solute concentration is lower in the cell than in the solution Cell loses water through osmosis Animal cell shrivels; plant cell plasmolyzes

77. LE 5-17 Isotonic solution Hypotonic solution Hypertonic solution H2OH2O H2OH2O (1) Normal (2) Lysed H2OH2O H2OH2O H2OH2O H2OH2O Animal cell Plant cell (4) Flaccid(5) Turgid(6) Shriveled (plasmolyzed) (3) Shriveled Plasma membrane H2OH2O H2OH2O

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79. Video: Plasmolysis Video: Plasmolysis Video: Turgid Elodea Video: Turgid Elodea

80. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.18 Cells expend energy for active transport Active transport requires energy to move solutes against a concentration gradient – ATP supplies the energy – Transport proteins move solute molecules across the membrane Animation: Active Transport Animation: Active Transport

81. LE 5-18 Transport protein Solute ATP P ADP Protein changes shape P Solute bindingPhosphorylation Transport Protein reversion Phosphate detaches P

82. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.19 Exocytosis and endocytosis transport large molecules To move large molecules or particles through a cell membrane – A vesicle may fuse with the membrane and expel its contents outside the cell (exocytosis) – Membranes may fold inward, enclosing material from the outside (endocytosis)

83. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5.19 Exocytosis and endocytosis transport large molecules To move large molecules or particles through a cell membrane – A vesicle may fuse with the membrane and expel its contents outside the cell (exocytosis) – Membranes may fold inward, enclosing material from the outside (endocytosis)

84. LE 5-19a Vesicle Fluid outside cell Protein Cytoplasm

85. LE 5-19b Vesicle forming

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87. Endocytosis can occur in three ways – Phagocytosis ("cell eating") – Pinocytosis ("cell drinking") – Receptor-mediated endocytosis

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90. LE 5-19c Pseudopodium of amoeba Phagocytosis Plasma membrane Food being ingested Material bound to receptor proteins PIT Cytoplasm Receptor-mediated endocytosis TEM 54,000  TEM 96,500  LM 230  Pinocytosis

91. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Receptor-Mediated Endocytosis Animation: Receptor-Mediated Endocytosis Animation: Exocytosis and Endocytosis Introduction Animation: Exocytosis and Endocytosis Introduction Animation: Exocytosis Animation: Exocytosis Animation: Pinocytosis Animation: Pinocytosis Animation: Phagocytosis Animation: Phagocytosis

92. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 5.20 Faulty membranes can overload the blood with cholesterol Cholesterol is carried in the blood by low- density lipoprotein (LDL) particles Normally, body cells take up LDLs by receptor- mediated endocytosis Harmful levels of cholesterol can accumulate in the blood if membranes lack cholesterol receptors – People with hypercholesterolemia have more than twice the normal level of blood cholesterol

93. LE 5-20 Phospholipid outer layer LDL particle Cholesterol Protein Plasma membrane Receptor protein Vesicle Cytoplasm