1. Ground Rules of Metabolism Chapter 5 Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole, Cengage Learning 2011. Biology, Ninth Edition, by Solomon, Berg, Martin. Brooks/Cole, Cengage Learning 2011.

2. 5.1 Energy and the World of Life  Energy: The capacity to do work Potential energy  Stored energy Example: chemical bonds Kinetic energy  Energy of motion

3. Two Laws of Thermodynamics 1 st Law. Energy cannot be created or destroyed It can be converted from one form to another and transferred between objects or systems Energy = Capacity to do work 2 nd Law. Entropy tends to disperse spontaneously Entropy tends to increase Some energy disperses at each energy transfer, usually in the form of heat Entropy = measure of how much work the energy system is dispersed

4. Energy In, Energy Out  Chemical reactions Reaction  Process of chemical change Reactants  molecules that enter a reaction Products  molecules produced from the reaction  Endergonic reactions  energy-requiring Photosynthesis  Exergonic reactions  energy-releasing Aerobic respiration

5. Exergonic and Endergonic Reactions

6. Energy Flows in One Direction  Energy is not cycled In from the sun; into and out of ecosystems  All living things harvest external energy Producers and consumers use energy to assemble, rearrange, and dispose of substances  Substances cycle among organisms over time

7. Fig. 5.4, p. 75 ENERGY OUT With each conversion, there is a one-way flow of a bit of energy back to the environment. Nutrients cycle between producers and consumers. NUTRIENT CYCLING producers consumers ENERGY OUT Energy continually flows from the sun. ENERGY IN Sunlight energy reaches environments on Earth. Producers of nearly all ecosystems secure some and convert it to stored forms of energy. They and all other organisms convert stored energy to forms that can drive cellular work. One-Way Energy Flow

8. Key Concepts: THE NATURE OF ENERGY FLOW  Energy tends to disperse spontaneously  Each time energy is transferred, some of it disperses  Organisms maintain their complex organization only by continually harvesting energy

9. 5.2 ATP in Metabolism  Adenosine triphosphate (ATP) Main energy carrier between cell reaction sites Couples endergonic reactions with exergonic reactions in cells ADP/ATP cycle  process cells produce ATP ADP + P  ATP ATP – P  ADP  Phosphorylation Phosphate-groups transfer to and from ATP Couple metabolic reactions that release usable energy to metabolic reactions

10. ATP: Energy Currency of Life

11. 5.3 Enzymes in Metabolism  Activation energy Minimum energy needed to start a reaction  Enzymes are catalysts Catalysts speed reaction rates by lowering activation energy Catalysts are unchanged by the reaction Most are proteins (some RNAs)

12. Activation Energy

13. Enzyme Structure  Active site Small cleft in enzyme’s surface where reactions occur Substrate binds to enzyme in the active site and a reaction takes place Microenvironment is more favorable for reaction than the surroundings

14. Enzyme Action  How enzymes lower activation energy By concentrating substrate molecules Substrate is acted upon by a enzyme By orienting substrates to favor reaction By inducing fit between substrate and active site By excluding water from active site Water can interfere with reactions  Activation energy allows enzyme to bring substrate to transition state  Product results

15. Enzyme Action: Hexokinase

16. Enzymes and the Environment  Each enzyme functions best within a characteristic range of temperature, salt concentration, and pH

17. Enzymes and pH

18. Cofactors  Most enzymes require assistance of cofactors Associates with an enzyme and is necessary for the enzyme to function. Types: Inorganic metal ions Organic coenzymes (vitamins)  Example: Catalase (Antioxidant) Cofactor: Iron Antioxidants  substance that prevents molecules form reacting with oxygen

19. Key Concepts: ENERGY, ATP, AND ENZYMES  ATP couples metabolic reactions that release usable energy with reactions that require energy  On their own, metabolic reactions proceed too slowly to sustain life  Enzymes increase reaction rates  Environmental factors influence enzyme activity

20. 5.5 Metabolism – Organized, Enzyme-Mediated Reactions  Metabolic pathways Series of enzyme-mediated reactions Cells concentrate, convert, and dispose of most substances in orderly, enzyme-mediated reaction sequences

21. 5.4 Controls Over Enzymes  Allosteric sites Enzyme binding site other than active site Bind regulatory molecules Alters shape of enzyme to enhance or inhibit function  Feedback inhibition Controls over enzyme activity adjust types and amounts of substances in cells Some activity decreases or stops the activity Negative Feedback  Temperature regulation Some activity increases activity Positive Feedback  Labor and blood clotting

22. Allosteric Control

23. Feedback Inhibition

24. Biosynthetic Pathways  Biosynthetic pathways Construct large molecules from smaller ones Require energy  Photosynthesis Main biosynthetic pathway in the biosphere Autotrophs

25. Degradative Pathways  Degradative pathways Break down molecules to smaller products Release usable energy  Aerobic respiration Main degradative pathway in the biosphere Heterotrophs

26. Main Metabolic Pathways

27. REDOX Reactions  Oxidation–reduction (redox) reactions Electron transfers used in metabolic pathways Oxidation  loss electrons/energy Reduction  gain electrons/energy  Coenzymes and electron transfer chains Take part in organized sequences of reactions in photosynthesis and aerobic respiration Molecules accept and give up electrons in sequence, thus releasing the energy of the electrons

28. Controlled Energy Release

29. ATP, Coenzymes, and Metabolic Pathways

30. Key Players in Metabolic Pathways

31. Key Concepts: THE NATURE OF METABOLISM  Metabolic pathways are energy-driven sequences of enzyme-mediated reactions  They concentrate, convert, or dispose of materials in cells  Controls over enzymes that govern key steps in these pathways can shift cell activities fast

32. 5.6 Diffusion, Membranes, and Metabolism  Concentration of a substance Number of atoms or molecules in a given volume  Concentration gradient of a substance A difference in concentration between two regions  Diffusion Net movement of molecules to a region where they are less concentrated  Diffusion rates are influenced by**: Temperature Molecular size Gradients of pressure, charge, and concentration

33. Diffusion

34. Diffusion and Membrane Permeability  Selective Permeability

35. How Substances Cross Membranes: Diffusion, Passive and Active Transport

36. Which Way Will Water Move?  Osmosis The diffusion of water across a selectively permeable membrane Water molecules follow their concentration gradient, influenced by solute concentration

37. Osmosis

38. Tonicity  Relative concentrations of two solutes separated by a semipermeable membrane Hypertonic fluid  higher solute concentration Hypotonic fluid  lower solute concentration Isotonic solutions  two solutions with the same tonicity

39. A Tonicity Experiment

41. Effects of Fluid Pressure  Hydrostatic pressure  turgor supports plants Exerts pressure on cell walls of plants and water stops diffusing into its cytoplasm Most prokaryotes, algae, plants, and fungi have rigid cell walls that can withstand a hypotonic solution without bursting Water moves into the cells by osmosis, building up turgor pressure against the rigid cell walls Turgor pressure is important in supporting the body of nonwoody plants  Osmotic pressure The amount of hydrostatic pressure/turgor that can stop water from diffusing into a hypertonic solution

42. Effects of Fluid Pressure  Osmotic pressure The amount of hydrostatic pressure/turgor that can stop water from diffusing into a hypertonic solution

43. Plasmolysis  If a cell that has a cell wall is placed in a hypertonic solution, the cell shrinks, and the plasma membrane separates from the cell wall (plasmolysis)  Plasmolysis occurs in plants when the soil or water around them contains high concentrations of salts or fertilizers

44. Turgor Pressure and Plasmolysis

45. 5.7 Working With and Against Gradients  Many solutes cross membranes through transport proteins (open or gated channels)  Facilitated diffusion (passive transport) does not require energy input Solute diffuses down its concentration gradient through a transporter Example: Glucose transporters

46. Facilitated Diffusion

47. Fig. 5.19, p. 85 passive transport protein glucose transporter Extracellular Fluid glucose, more concentrated outside cell than inside Cytoplasm Lipid Bilayer

48. Fig. 5.19, p. 85

49. Facilitated Diffusion of Glucose

50. Active Transport  Active transporters require ATP energy to move a solute against its concentration gradient Maintain gradients across cell membranes Example: Calcium pumps  Cotransporters move two substances at the same time either in the same or different directions Antiporter  Sodium-potassium pump Symporters  Glucose-Sodium pump

51. Active Transport: Calcium Pump

52. Fig. 5.20, p. 86 An ATP molecule binds to a calcium pump. higher concentration of calcium ions outside cell compared to inside calcium pump The shape of the pump returns to its resting position.

53. Fig. 5.20, p. 86 The ATP transfers a phosphate group to pump. The energy input causes the pump’s shape to change. ADP + P i The shape change permits calcium to be released to opposite side of membrane. A phosphate group and ADP are released. Calcium enters a tunnel through the pump, binds to functional groups inside.

54. The Sodium–Potassium Pump sodium–potassium pump Counter-transport uses energy from ATP to pump sodium ions out of the cell and potassium ions into the cell 2 potassium ions are imported 3 sodium ions exported An electrical potential (separation of electric charges) is generated across the membrane

55. Fig. 5-17a, p. 122 Higher Outside cell Lower Active transport channel Sodium concentration gradient Potassium concentration gradient LowerCytosolHigher (a) The sodium–potassium pump is a carrier protein that requires energy from ATP. In each complete pumping cycle, the energy of one molecule of ATP is used to export three sodium ions (Na + ) and import two potassium ions (K + ).

56. Fig. 5-17b, p. 122 (b) Follow the steps illustrating a model of active transport by the sodium–potassium pump. 1 23 4 56

57. Cotransport of Glucose and Sodium Ions

58. 5.8 Membrane Traffic To and From the Cell Surface  Exocytosis Cytoplasmic vesicle fuses with plasma membrane Contents are released outside  Endocytosis Part of plasma membrane forms a vesicle that sinks into the cytoplasm

59. How Substances Cross Membranes: Endocytosis and Exocytosis

60. Types of Endocytosis  Receptor-mediated endocytosis Substance binds to surface receptors Pit forms endocytotic vesicle  Phagocytosis  “cell eating” Amoebas use pseudopods to engulf prey  Pinocytosis  “cell drinking”

61. Endocytosis and Exocytosis

62. Fig. 5.24, p. 88 Some vesicles are routed to the nuclear envelope or ER membrane. Others fuse with Golgi bodies. EndocytosisExocytosis coated pit Molecules get concentrated inside coated pits at the plasma membrane. The pits sink inward and become endocytic vesicles. Vesicle contents are sorted. Some vesicles and their contents are delivered to lysosomes. Many of the sorted molecules cycle to the plasma membrane.

63. Phagocytosis

64. Pinocytosis

65. Key Concepts: MEMBRANES AND METABOLISM  Concentration gradients drive the directional movements of ions and molecules into and out of cells  Transport proteins raise and lower water and solute concentrations across the plasma membrane and internal cell membranes  Other mechanisms move larger cargo across the plasma membrane

66. Key Concepts: METABOLISM EVERYWHERE  Knowledge about metabolism, including how enzymes work, can help you interpret what you see in nature

67. Animation: Activation energy

68. Animation: Allosteric activation

69. Animation: Allosteric inhibition

70. Animation: Energy changes in chemical work

71. Animation: Enzymes and temperature

72. Animation: Feedback inhibition

73. Animation: One-way energy flow and materials cycling

74. Animation: Structure of ATP