Chapter 6 Study Guide An Introduction to Metabolism AP Biology, Mrs. Beebe 1. The totality of an organism’s chemical processes is called _____________. 2. Some metabolic pathways release energy by breaking down complex molecules to simpler compounds. These degradative processes are called ____________pathways. 3. A major thoroughfare of catabolism is ________________ _______________ in which the sugar, ____________ and other organic fuels are broken down to ____________ ____________and _____________. 4. ______________pathways consume energy to build complicated molecules from simpler ones. An example is the synthesis of ___________from amino acids. 5. The metabolic pathways intersect in such a way that energy _____________ from the “downhill” reactions of catabolism can be used to ___________the “uphill” reactions of anabolic pathways. 6. bioenergetics: 7. _______________is the capacity to do work, or to ____________a collection of matter. 8. chemical energy is to _________energy as heat is to kinetic energy. 9. The study of energy transformations that occur in a collection of matter is called ___________________. 10. first law of thermodynamics: 11. second law of thermodynamics: 12. entropy: 13. In most energy transformations, ordered forms of energy are at least partly converted to __________. Only about _____% of the chemical energy stored in the fuel tank of an automobile is transformed into the motion of the car; the remaining ______% is lost from the engine as heat which dissipates rapidly through the surroundings. 14. In machines and organisms, even the energy that performs useful work is eventually converted to ____________. 15. Energy flows into an ecosystem in the form of ____________and exits the ecosystem in the form of ____________. 16. Organisms are islands of low ___________in an increasingly random universe. 17. Spontaneous changes occur without outside ___________; they may be harnessed to perform _____________; when spontaneous changes occur, the stability of the system _________________. A process can occur spontaneously only if it (increases/decreases) entropy. 18. _____________ _____________ is the portion of a system’s energy that can perform work when temperature is uniform throughout the system. Organisms live only at the expense of free energy acquired from the ________________. 19. What do each of the letters in the following equation stand for?: G = H - TS 20. What does this equation tell us about free energy? 21. Systems that are rich in energy are ____________; so are highly ordered systems, such as complex molecules. Thus those systems that tend to change spontaneously to a more stable state are those that have _________energy, _________entropy or both. 22. In any spontaneous process, the free energy of a system (increases/decreases.) 23. Give the equation for a change in the free energy as a system goes from a starting state to a different state using the variables G, H, T, S. 24. For a process to occur spontaneously, the system must either give up ___________, (a decrease in H) give up ____________(an increase in S) or both. When these changes in H and S are tallied, ∆G must have a negative value. 25. The ∆G value of a reaction at chemical equilibrium is ______________. 26. Exergonic reactions proceed with a net ___________of free energy. ∆G is __________. In other words, exergonic reactions are those that occur ______________. 27. Endergonic reactions ______________free energy from the surroundings. This kind of reaction ___________free energy, so ∆G is ____________. Such reactions are nonspontaneous and the magnitude of ∆G for an exergonic reaction is the quantity of energy required to ___________the reaction. 28. If a chemical process is exergonic in one direction, then the reverse process must be ________________. 29. Respiration is an ________________process, while photosynthesis is steeply ________________, an uphill process powered by the absorption of light energy from the sun. 30. Chemical reactions of metabolism are reversible and would reach equilibrium if they occurred in the isolation of a test tube. This is incompatible with life, ______________ _______________ is one of the defining features of life. The key to sustaining disequilibrium is that the _____________of one reaction does not accumulate, but instead becomes a ______________in the next step along the metabolic pathway. The overall sequence of reactions is pulled by the huge free energy difference between the initial reactants and the final products. 31. A key strategy in bioenergetics is _______________ _______________, the use of an exergonic process to drive an endergonic one. A molecule called ________ is responsible for mediating most energy coupling in cells. ATP stands for _____________ __________________. 32. What are 3 main kinds of work done by cells? a. b. c. 33. The structure of ATP is closely related to the _______________nucleotide of RNA. 34. The RNA nucleotide has _____phosphate group(s) attached to ribose, but ATP has a chain of _______phosphate group(s) attached to the ribose. 35. The bonds between the phosphate groups of ATP’s talil can be broken by ________________. When this happens a molecule of inorganic phosphate leaves the ATP, which becomes ______________ _______________ or ADP. The reaction is _____________ and release ________kcal of energy per mole of ATP hydrolyzed. 36. When this reaction occurs in a cellular environment the actual ∆G is about _________kcal/mole. 37. Why does the breaking of these bonds release so much energy? 38. How does ATP actually perform work for a cell? 39. ATP is a renewable resource that can be regenerated by the addition of _____________ to ADP. Since the breakdown of ATP to ADP releases energy, the regeneration of ATP from ADP is necessarily _______________. The energy necessary for the regeneration of ATP comes from ____________pathways, especially cellular respiration. 40. Even spontaneous chemical reactions may occur too ___________for life processes. _____________speed up metabolic reactions by _______________ energy barriers. 41. Enzymes are ______________ ______________. 42. catalyst: 43. Every chemical reaction involves both bond___________ and bond ______________. The reactant molecules must absorb energy from their surroundings for their bonds to break. Energy is ____________ when the new bonds of the product molecules are formed. 44. The initial investment of energy for starting a reaction-the energy required to ___________bonds in the ___________molecules-is known as the : ______________________________, or _______________ _____________. It is usually provided in the form of _____________that the reactant molecules absorb from the surroundings. If the reaction is exergonic, the initial investment of energy to start the reaction will be repair with dividends, as the formation of new bonds releases more energy than was invested in the breaking of old bonds. 45. Draw the energy profile of the reaction: AB + CD → AC + BD. (Copy Fig. 6.9) 46. For some reactions, EA is modest enough that even at room temperature, there is sufficient thermal energy for the reaction to occur. This is not the case for the combustion of gasoline in an automobile engine. How is this problem overcome? 47. Why is the barrier of activation energy essential for life? 48. High temperatures kill cells, so how do cells surmount the barrier of activation energy? Explain. 49. Enzymes are very ____________ in the reactions they catalyze, so they determine which chemical processes will be going on in the cell at any particular time. 50. The _______________an enzyme acts on is the substrate. 51. What happens when the enzyme binds to the substrate? 52. Can an enzyme distinguish isomers? 53. The specificity of an enzyme is the result of its _____________. 54. What is the active site? 55. How is the active site formed? 56. The specificity of an enzyme is attributed to a ____________ _______ between the shape of its active site and the shape of the substrate. 57. What happens to the active site as the substrate enters it, and what is this called? 58. Induced fit can be thought of like a ______________ ___________________. 59. What is the purpose of induced fit? 60. How is the substrate held in the active site? 61. What exactly catalyzes the reaction? 62. What happens after the substrate has been converted to product? 63. The reaction is very (fast/slow) and very (small/large) amounts of enzyme can have a huge metabolic impact by functioning over and over again in catalytic cycles. 64. Describe 3 ways that enzymes lower the activation energy and speed up a reaction. a. b. c. 65. The rate of the conversion of substrate to product is partly a function of the ________________ _______________ of substrate. But when an enzyme population is saturated, the only way to increase productivity is to add more ________________. 66. What are 4 environmental/chemical factors that affect enzyme activity? a. b. c. d. 67. How does temperature affect enzyme activity? Explain how optimal and high temperatures affect activity. 68. Most human enzymes have optimal temperatures of about _______ to ________. 69. How does pH affect enzyme activity? Explain how optimal and extreme variations in ph affect an enzyme. 70. Most enzymes operate in pH of ___to____. Pepsin a stomach enzyme works best at pH_____. 71. What does it mean to denature an enzyme? 72. cofactor: 73. If a cofactor is an organic molecule it is called a ______________. Most ____________ are coenzymes. 74. What are 2 types of enzyme inhibitors? 75. How do competitive inhibitors work, and how can they be overcome. Are they reversible? 76. How do noncompetitive inhibitors work? 77. In many cases, the molecules that naturally regulate enzyme activity in a cell behave something like reversible _______________inhibitors. 78. These regulatory molecules change an enzyme’s shape and function by binding to an ____________ ___________, a specific receptor site on some part of the enzyme molecule remote from the active site. The effect may be either inhibition or stimulation of the enzyme’s activity. 79. An enzyme regulated in this way has two forms, active and inactive. The binding of an ______________to an allosteric site stabilizes the conformation that has a functional active site, whereas the binding of an allosteric __________________ stabilizes the inactive form of the enzyme. 80. Allosteric regulators attach to an enzyme by weak bonds, so the activity of the enzyme changes in response to fluctuating _____________of the regulators. 81. Feedback inhibition is one way that the rates of metabolic reactions can be controlled. Describe feedback inhibition. 82. Describe cooperativity using the words: induced fit, subunits, ampify(ies). 83. How is the location of enzymes coordinated with the function of those enzymes?
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