1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 08 An Introduction to Metabolism

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The living cell is a miniature chemical factory where thousands of reactions occur The cell extracts energy and applies energy to perform work Some organisms even convert energy to light, as in bioluminescence Overview: The Energy of Life

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metabolic pathways in a cell

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What causes the bioluminescence in these organisms Figure 8.1 Bioluminescence: 특정 유기산에 저장된 에너지를 빛으로 전환하는 과정

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.1: An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics Metabolism ( 물질대사 ) is the totality of an organism’s chemical reactions Metabolism is an emergent property of life that arises from interactions between molecules within the cell

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Organization of the Chemistry of Life into Metabolic Pathways A metabolic pathway ( 대사경로 ) has many steps –That begin with a specific molecule and end with a product –That are each catalyzed by a specific enzyme Enzyme 1Enzyme 2Enzyme 3 A B C D Reaction 1Reaction 2Reaction 3 Starting molecule Product

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metabolism 의 분류 Catabolic pathways ( 이화작용 경로 ) –Break down complex molecules into simpler compounds –Release energy ( 예 : 세포호흡 ) Anabolic pathways ( 동화작용 경로 ) –Build complicated molecules from simpler ones –Consume energy ( 예 : 단백질합성 ) 생명체의 대사경로는 에너지를 기반으로 발생하므로 세포의 활동을 이해하기 위해서는 에너지에 대한 기초지식이 필요

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 에너지 형태에는 어떤 것이 있나 ? Energy – Is the capacity to cause change – Exists in various forms, of which some can perform work

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Kinetic energy ( 운동에너지 ) –Is the energy associated with motion Heat or thermal energy ( 열 또는 열에너지 ) - Is kinetic energy associated with the random movement of atoms or molecules Potential energy ( 위치 에너지 ) : 물질의 위치나 구조 덕분에 갖게 되는 저장된 형태의 에너지 –Is stored in the location of matter ( 활동적이지 않으며 비축된 에너지 형태 ) –Includes chemical energy stored in molecular structure ( 예 : ATP) –Chemical energy ( 화학에너지 ) 는 화학반응에서 방출되는 위치에너지

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy can be converted : From one form to another ( 에너지 형태는 전환가능함 ) Figure 8.2 운동에너지와 위치에너지 사이의 전환 (Transformations between potential and kinetic energy) A diver has more potential energy on the platform than in the water. Diving converts potential energy to kinetic energy. Climbing up converts the kinetic energy of muscle movement to potential energy. A diver has less potential energy in the water than on the platform.

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Laws of Energy Transformation Thermodynamics ( 열역학 ) – Is the study of energy transformations ( 물질을 포함하는 우주 속에서의 에너지 변환에 관한 학문 ) System ( 계 ) Surroundings ( 주변부 ) : system 을 뺀 우주의 나머지 부분 물질과 에너지의 양방향 이동이 가능 : 생물과 같이 열린계 (open system) 의 경우

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The First Law of Thermodynamics ( 에너지 보존의 법칙 ) 곰이 획득한 연어로부터 전환된 화학에너지는 운동에너지 등으로 변환될 수 있음. 그러면 과연 이런 운동에너지의 운명은 ? According to the first law of thermodynamics, the energy of the universe is constant - energy can be transferred and transformed, but it cannot be created or destroyed (a) First law of thermodynamics Chemical energy Fig. 8.3a  에너지 전환의 예

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Second Law of Thermodynamics During every energy transfer or transformation, some energy is unusable, and is often lost as heat According to the second law of thermodynamics – Every energy transfer or transformation increases the entropy (disorder) of the universe 모든 형태의 에너지 이동이나 전환은 우주의 무질서도 ( 엔트로피 ) 를 증가시킨다

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – 곰이 획득한 에너지 중 변환된 형태의 화학에너지는 움직임으로 변환됨. – 대부분은 열 또는 대사의 부산물인 이산화탄소나 물 등의 분자로 바뀌어 주변부로 전달되어 우주의 무질서도를 증가시키게 됨 Figure 8.3b (b) Second law of thermodynamics Heat

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biological Order and Disorder Cells create ordered structures from less ordered materials Organisms also replace ordered forms of matter and energy with less ordered forms Energy flows into an ecosystem in the form of light and exits in the form of heat The evolution of more complex organisms does not violate the second law of thermodynamics Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases ( 생명체내의 질서 유지에는 에너지가 필요함 )

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.4 질서는 생명체의 특성이다 성게 (sea urchin) 선인장

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.2: The free-energy change of a reaction tells us whether the reaction occurs spontaneously Biologists want to know which reactions occur spontaneously and which require input of energy To do so, they need to determine energy changes that occur in chemical reactions

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings –Free-Energy Change,  G (for J. Williard Gibbs, Prof. at Yale Univ. in 1878) 자유에너지 변화란 무엇인가 ? A living system’s free energy is energy that can do work when temperature and pressure are uniform, as in a living cell 화학반응의 자유에너지 변화를 알게 되면 화학반응이 자발적으로 일어나는 지 아니면 에너지 투입이 필요한 것인지를 이해하게 된다

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The change in free energy, ∆G during a biological process –Is related directly to the enthalpy change (∆H) and the change in entropy ( ∆S) ∆G = ∆H – T∆S [T: K( 켈빈 ) 단위의 절대온도 ]  ∆G 은 화학반응이 외부 에너지 공급없이 자발적으로 일어날 수 있는 지 없는 지를 결정하는 데 이용될 수 있음 ∆G < 0 : 자발적인 반응 ( 자유에너지 감소 ; 엔탈피 감소, 엔트로피 증가와 관련됨 )

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Free Energy, Stability, and Equilibrium 생명체는 자유에너지 소모를 통해 안정한 계가 되려고 한다 : ∆G = G final - G first During a spontaneous change –Free energy decreases and the stability of a system increases – 모든 계는 안정도가 높아지는 방향 또는 자유에너지는 감소하는 방향으로 가는 경향 있음 – 안정성이 최고조인 상태를 “ 평형 (equilibrium)” 이라 함

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 안정성이 최고조인 상태를 “ 평형 (equilibrium)” 이라 함 Figure 8.5 More free energy (higher G) Less stable Greater work capacity In a spontaneous change The free energy of the system decreases (  G  0) The system becomes more stable The released free energy can be harnessed to do work Less free energy (lower G) More stable Less work capacity (a) Gravitational motion (b) Diffusion(c) Chemical reaction 확산 화학반응중력운동 자유에너지, 안정화, 일능력, 자발적인 변화의 관계 ? 염료 분자 포도당의 분해과정 다이빙 계의 안정성이 최고치에 도달한 것이 평형이다

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 자유에너지 개념은 생명체의 물질대사에도 적용될 수 있다 ! Exergonic ( 발열 ) and Endergonic ( 흡열 ) Reactions in Metabolism An exergonic reaction –Proceeds with a net release of free energy and is spontaneous ( 자유에너지 방출 / 자발적 ) Figure 8.6 Reactants Products Energy Progress of the reaction Amount of energy released (∆G <0) Free energy (a) Exergonic reaction: energy released

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An endergonic reaction –Is one that absorbs free energy from its surroundings and is nonspontaneous ( 주변부로부터 자유에너지 흡수 / 비자발적 ) Figure 8.6 Energy Products Amount of energy released (∆G>0) Reactants Progress of the reaction Free energy (b) Endergonic reaction: energy required

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Equilibrium and Metabolism ( 평형과 물질대사 ) 평형에 도달하는 것은 생명체에게는 죽음이다 그렇다면 생명체는 어떻게 평형에 도달하지 않고 살아 갈 수 있나 ?

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reactions in a isolated system – Eventually reach equilibrium – 닫힌 계에서는 평형상태로 가게 되며, 일을 할 수 없게 됨. Figure 8.7 A (a) A isolated hydroelectric system. Water flowing downhill turns a turbine that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium. ∆G < 0 ∆G = 0 페쇄된 수력발전

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cells in our body (= 열린계 ) – Experience a constant flow of materials in and out, preventing metabolic pathways from reaching equilibrium ( 물질의 계속적인 출입현상이 일어나므로 대사과정이 평형에 도달하는 것을 방지함 ) Figure 8.7 (b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equlibrium. ∆G < 0 열린 수력발전

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 영생의 길은 가능한 가 ? An analogy for cellular respiration ( 세포호흡은 다단계로 구성된 열린 수력발전 계와 유사함 ) Figure 8.7 (c) A multistep open hydroelectric system. Cellular respiration is analogous to this system: Glucoce is brocken down in a series of exergonic reactions that power the work of the cell. The product of each reaction becomes the reactant for the next, so no reaction reaches equilibrium. ∆G < 0 산소 + 포도당 이산화탄소 + 물 세포에서는 연료인 포도당과 산소를 공급받을 수 있고, 이산화탄소 및 물과 같은 노폐물 제거가 지속적으로 가능하다면 평형에 도달하지 않고 생명체로서 영원히 일을 수행할 수 있음

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions A cell does three main kinds of work – Mechanical ( 기계적인 ) : 편모, 섬모의 운동성, 근수축 등 – Transport ( 수송 작업 ): 막단백질에 의한 능동수송 등 – Chemical ( 화학적 작업 ): 광합성에 의한 중합체 합성 등

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 어떻게 이런 일들을 할 수 있을까 ? Energy coupling ( 에너지 연계 ) – Is a key feature in the way cells manage their energy resources to do this work – 세포가 여러 작업을 수행하는 데 있어 에너지 자원을 관리하는 방법 중 하나 – 발열반응을 이용하여 흡열반응을 수행하는 데 필요함 – ATP 는 세포내의 대부분의 에너지 연계에 필요한 직접적인 에너지원

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and Hydrolysis of ATP (a) The structure of ATP Phosphate groups Adenine Ribose ATP (adenosine triphosphate) is the cell’s energy shuttle ATP is composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups Figure 8.8

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy is released from ATP (ATP 로부터 에너지 방출 ) – When the terminal phosphate bond is broken Figure 8.8b Adenosine triphosphate (ATP) Energy Inorganic phosphate Adenosine diphosphate (ADP) (b) The hydrolysis of ATP

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How ATP Performs Work? The three types of cellular work (mechanical, transport, and chemical) are powered by the hydrolysis of ATP In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction Overall, the coupled reactions are exergonic ATP 에 의한 흡열반응의 유도는 인산화를 통해 인산기를 다른 분자 ( 흡열반응의 반응물 ) 에 전이시킴으로써 가능하며 결국 연계반응은 발열반응이 된다

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.9 Glutamic acid Ammonia Glutamine (b) Conversion reaction coupled with ATP hydrolysis Glutamic acid conversion to glutamine (a) (c) Free-energy change for coupled reaction Glutamic acid Glutamine Phosphorylated intermediate Glu NH 3 NH 2 Glu  G Glu = +3.4 kcal/mol ATP ADP NH 3 Glu P P i ADP Glu NH 2  G Glu = +3.4 kcal/mol Glu NH 3 NH 2 ATP  G ATP =  7.3 kcal/mol  G Glu = +3.4 kcal/mol +  G ATP =  7.3 kcal/mol Net  G =  3.9 kcal/mol 1 2 How ATP drives chemical work: Energy coupling using ATP hydrolysis

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.10 Transport protein Solute ATP P P i ADP P i ADP ATP Solute transported Vesicle Cytoskeletal track Motor proteinProtein and vesicle moved (b) Mechanical work: ATP binds noncovalently to motor proteins and then is hydrolyzed. (a) Transport work: ATP phosphorylates transport proteins. Q: How ATP drives transport and mechanical work?

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Regeneration of ATP (ATP 는 전지 ( 배터리 ) 와 같다 ) ATP is a renewable resource that is regenerated by addition of a phosphate group to adenosine diphosphate (ADP) The energy to phosphorylate ADP comes from catabolic reactions in the cell The ATP cycle is a revolving door through which energy passes during its transfer from catabolic to anabolic pathways

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ATP Cycle Catabolic pathways – Drive the regeneration of ATP from ADP and phosphate ATP synthesis from ADP + P i requires energy ATP ADP + P i Energy for cellular work (endergonic, energy- consuming processes) Energy from catabolism (exergonic, energy yielding processes) ATP hydrolysis to ADP + P i yields energy Figure 8.11 + H 2 O

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers ( 에너지장벽 ) A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction An enzyme is a catalytic protein Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How does the enzyme do this? Sucrase Sucrose (C 12 H 22 O 11 ) Glucose (C 6 H 12 O 6 ) Fructose (C 6 H 12 O 6 )

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 활성화 에너지 장벽 ? The activation energy, E A – Is the initial amount of energy needed to start a chemical reaction ( 화학반응의 개시에 필요한 에너지로 반응물을 전이상태로 끌어 올리는 데 사용됨 ) – Is often supplied in the form of heat from the surroundings in a system ( 종종 주변부로부터 열에너지 형태로 공급됨 ) – 반응속도를 결정하는 장벽 역할 – 열은 단백질변성, 세포죽음을 초래할 수 있고, 모든 반응에 작용하므로 특이성이 없음. – 따라서 생물계에서는 E A 장벽을 낮추는 대안으로 효소와 같은 촉매를 사용함

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.12 Transition state Reactants Products Progress of the reaction Free energy EAEA  G  O A B C D A B C D A B C D 반응물은 주변으로부터 충분한 에너지를 획득하여 불안정한 전이상태에 도달하게 되며 화학결합이 끊어지게 된다 화학결합이 절단된 후 새로운 결합이 생성되며 에너지가 주변으로 방출된다 발열반응의 에너지 흐름도

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How Enzymes Lower the E A Barrier? Enzymes catalyze reactions by lowering the E A barrier Enzymes do not affect the change in free energy (∆G); instead, they hasten (=hurry) reactions that would occur eventually

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.13 Course of reaction without enzyme E A without enzyme E A with enzyme is lower Course of reaction with enzyme Reactants Products  G is unaffected by enzyme Progress of the reaction Free energy An enzyme catalyzes reactions By lowering the E A barrier ( 높지 않은 보통 수준의 온도에서도 반응분자가 쉽게 전이상태에 도달할 수 있게 충분한 에너지를 흡수할 수 있게 E A 장벽을 낮춤. 이때 free-energy change 에는 영향을 미치지 않음 )

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Substrate Specificity of Enzymes ( 효소의 기질특이성 ) 효소의 작용기작은 ? The reactant that an enzyme acts on is called the enzyme’s substrate The enzyme binds to its substrate, forming an enzyme-substrate complex The active site is the region on the enzyme where the substrate binds Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction ( 활성부위는 기질의 화학그룹에 맞게 적합한 형태로 전환될 수 있음 )

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.14 Substrate Active site Enzyme Enzyme-substrate complex (a) (b) Hexokinase and glucose Induced fit between an enzyme and its substrate

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Catalysis in the Enzyme’s Active Site 효소의 활성부위는 어떻게 활성화 에너지 장벽을 낮추나 ? In an enzymatic reaction, the substrate binds to the active site of the enzyme The active site can lower an E A barrier by – Orienting substrates correctly ( 기질의 정확한 배열 유도 ) – Straining substrate bonds ( 기질결합을 압박하여 전이상태 안정화 ) – Providing a favorable microenvironment ( 우호적인 미세환경 제공 ) – Covalently bonding to the substrate ( 촉매반응에 직접 참여하여 기질과 공유결합 형성 )

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The catalytic cycle of an enzyme Substrates Products Enzyme Enzyme-substrate complex 1 Substrates enter active site; enzyme changes shape so its active site embraces the substrates (induced fit). 2 Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. 3 Active site (and R groups of its amino acids) can lower E A and speed up a reaction by acting as a template for substrate orientation, stressing the substrates and stabilizing the transition state, providing a favorable microenvironment, participating directly in the catalytic reaction. 4 Substrates are Converted into Products. 5 Products are Released. 6 Active site Is available for two new substrate Mole. Figure 8.15

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Effects of Local Conditions on Enzyme Activity The activity of an enzyme – Is affected by general environmental factors – Effects of Temperature and pH – Cofactors: nonprotein enzyme helpers Zn, Fe, Cu ( 아연, 철, 구리와 같은 무기이온 ) or coenzyme such as vitamins (organic) – Enzyme Inhibitors

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Enzyme Inhibitors Competitive inhibitors bind to the active site of an enzyme, competing with the substrate Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective Examples of inhibitors include toxins, poisons, pesticides, and antibiotics

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.17 (a) Normal binding(b) Competitive inhibition (c) Noncompetitive inhibition Substrate Active site Enzyme Competitive inhibitor Noncompetitive inhibitor 효소 활성의 억제는 어떻게 일어나나 ?

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.5: Regulation of enzyme activity helps control metabolism Chemical chaos would result if a cell’s metabolic pathways were not tightly regulated A cell does this by switching on or off the genes that encode specific enzymes or by regulating the activity of enzymes

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Allosteric Regulation of Enzymes Allosteric regulation may either inhibit or stimulate an enzyme’s activity Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site Allosteric regulation 은 조절인자가 표적단백질의 특정 부위에 결합했을 때 다른 부위에 고유한 단백질의 기능이 영향을 받는 현상을 말한다.

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Allosteric Activation and Inhibition Most allosterically regulated enzymes are made from polypeptide subunits Each enzyme has active and inactive forms The binding of an activator stabilizes the active form of the enzyme The binding of an inhibitor stabilizes the inactive form of the enzyme

53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.19a Regulatory site (one of four) (a) Allosteric activators and inhibitors Allosteric enzyme with four subunits Active site (one of four) Active form Activator Stabilized active form Oscillation Nonfunctional active site Inactive form Inhibitor Stabilized inactive form

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.19b Inactive form Substrate Stabilized active form (b) Cooperativity: another type of allosteric activation that can amplify enzyme activity 한 개의 subunit 에 기질결합으로 나머지 subunit 도 활성화시키는 현상

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Scientific Inquiry: Identification of Allosteric Regulators via drug screening Allosteric regulators are attractive drug candidates for enzyme regulation because of their specificity Inhibition of proteolytic enzymes called caspases may help management of inappropriate inflammatory responses

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.20 Caspase 1 Active site Substrate SH Known active form Active form can bind substrate Allosteric binding site Allosteric inhibitor Hypothesis: allosteric inhibitor locks enzyme in inactive form Caspase 1 Active formAllosterically inhibited form Inhibitor Inactive form EXPERIMENT RESULTS Known inactive form Allosterically inhibited form 이 active form 또는 inactive form 중 어는 것에 더 가까운 지를 판단해 보시오.

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Feedback Inhibition In feedback inhibition, the end product of a metabolic pathway shuts down the pathway Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.21 Active site available Isoleucine used up by cell Feedback inhibition Active site of enzyme 1 is no longer able to catalyze the conversion of threonine to intermediate A; pathway is switched off. Isoleucine binds to allosteric site. Initial substrate (threonine) Threonine in active site Enzyme 1 (threonine deaminase) Intermediate A Intermediate B Intermediate C Intermediate D Enzyme 2 Enzyme 3 Enzyme 4 Enzyme 5 End product (isoleucine) 이소류신 생합성과정에 서의 피드백 억제

59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings a)yes b)no c)only the exergonic reactions d)all reactions except those powered by ATP hydrolysis Are most chemical reactions at equilibrium in living cells? 8 장이 끝났습니다. 이제 절반을 공부했군요. 수고했습니다.