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1 Energy and Metabolism Chapter 6. Section 6.1 Learning Objectives –The Flow of Energy in Living Systems Differentiate between kinetic and potential energy.

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Presentation on theme: "1 Energy and Metabolism Chapter 6. Section 6.1 Learning Objectives –The Flow of Energy in Living Systems Differentiate between kinetic and potential energy."— Presentation transcript:

1 1 Energy and Metabolism Chapter 6

2 Section 6.1 Learning Objectives –The Flow of Energy in Living Systems Differentiate between kinetic and potential energy. Identify the source of energy for the biosphere (Earth). Contrast oxidation and reduction reactions. 2

3 3 Flow of Energy Thermodynamics –Branch of chemistry concerned with energy changes –Study of energy flow or transformations Kinetic energy  potential energy Potential energy  kinetic energy Cells are governed by the laws of physics and chemistry

4 What is Energy? Energy – capacity to do work –2 states 1.Kinetic – energy of motion 2.Potential – stored energy –Many forms – mechanical, heat, sound, electric current, light, or radioactivity –Heat the most convenient way of measuring energy 1 calorie = heat required to raise 1 gram of water 1ºC calorie or Calorie? –Calorie (1000 calories) how food energy measured 4

5 5 a. Potential energy b. Kinetic energy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stored energy based on her position (also think of a bolder on top of a hill) Energy in motion (she is able to slide down based on her previous position)

6 The Source of Energy on Earth Energy flows into the biological world from the sun Photosynthetic organisms (plants/algae) capture this energy Stored as potential energy in chemical bonds (in sugars made from photosynthesis) 6 photosynthesis cell respiration

7 7 Redox reactions (how energy is transferred at molecular level) Oxidation –Atom or molecule loses an electron Reduction –Atom or molecule gains an electron –Higher level of energy than oxidized form Oxidation-reduction reactions (redox) –Reactions always paired –LEO says GER (leo is a lion) Loss of e - is oxidation Gain of e - is reduction

8 To follow the energy, follow the e - 8 e – AB A + B + A + B – Loss of electron (oxidation) LEO Gain of electron (reduction) GER Lower energyHigher energy e-e-

9 Question Oxidation is the ____________ and reduction is the ________. a.loss of electrons, gain of electrons b.gain of protons, loss of protons c.loss of protons, gain of protons d.loss of electrons, gain of protons

10 Section 6.2 Learning Objectives –The Laws of Thermodynamics and Free Energy Explain the laws of thermodynamics. Relate free energy changes to the outcome of chemical reactions. Contrast the course of a reaction with and without an enzyme catalyst. 10

11 Laws of thermodynamics First law of thermodynamics –Energy cannot be created or destroyed –Energy can only change from one form to another –Total amount of energy in the universe remains constant –During each conversion, some energy is lost as heat 11

12 12 Second law of thermodynamics –Entropy (disorder) is continuously increasing –Energy transformations proceed spontaneously to convert matter from a more ordered/less stable form to a less ordered/ more stable form

13 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Disorder happens spontaneously Organization requires energy © Jill Braaten

14 14 Free energy G = Energy available to do work G = H – TS  H = enthalpy, energy in a molecule’s chemical bonds  T = absolute temperature  S = entropy, unavailable energy G

15 ΔG = ΔH – TS ΔG = change in free energy Positive ΔG –Products have more free energy than reactants –Not spontaneous, requires input of energy –Endergonic (photosynthesis) Negative ΔG –Products have less free energy than reactants –Spontaneous (may not be instantaneous) –Exergonic (cell respiration) 15

16 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a.a. b.b. 0 0 Course of Reaction Products  G > 0  G < 0 Reactants Course of Reaction Products Free Energy (G) Energy Released Energy Supplied Free Energy (G) Energy Released Energy Supplied Energy is released Energy must be supplied Exergonic Endergonic photosynthesis cell respiration

17 Activation Energy: How to Start a Reaction Extra energy required to destabilize existing bonds and initiate a chemical reaction Exergonic reaction’s rate depends on the activation energy required –Larger activation energy proceeds more slowly Rate can be increased 2 ways 1.Increasing energy of reacting molecules (heating) 2.Lowering activation energy 17

18 18 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ΔGΔG Energy Released Energy Supplied Free Energy (G) Activation energy Activation energy 0 uncatalyzed catalyzed Course of Reaction Product Reactant

19 Catalysts Substances that influence chemical bonds in a way that lowers activation energy Cannot violate laws of thermodynamics –Cannot make an endergonic reaction spontaneous Do not alter the proportion of reactant turned into product 19

20 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ΔGΔG Energy Released Energy Supplied Free Energy (G) Activation energy Activation energy 0 uncatalyzed catalyzed Course of Reaction Product Reactant

21 Question The energy in a system that is able to do work is called a.Enthalpy b.Entropy c.Free energy d.Kinetic energy e.Potential energy

22 Question A reaction with a positive ∆G is – a.Exergonic b.Entropic c.Endergonic d.Enthalpic e.Energertic

23 Question A ball sitting atop a hill begins to roll down after getting a slight tap. This is analogous to an endergonic reaction. a.This is true b.This is false

24 Section Learning Objectives –ATP: The Energy Currency of Cells Describe the role of ATP in short-term energy storage. Distinguish which bonds in ATP are “high energy.” –Enzymes: Biological Catalysts Discuss the specificity of enzymes. Explain how enzymes bind to their substrates. List the factors that influence the rate of enzyme- catalyzed reactions. 24

25 25 ATP: Cell Energy Adenosine triphosphate Chief “currency” all cells use Composed of –Ribose – 5 carbon sugar –Adenine –Chain of 3 phosphates Key to energy storage Bonds are unstable ADP – 2 phosphates AMP – 1 phosphate – lowest energy form

26 26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. AMP CORE O O–O– O O O H HH H O CC N N N C N C CH H PO–O– OP O PO ADP ATP Triphosphate group O–O– CH 2 High-energy bonds a.a. Adenine NH 2 Ribose OH b.b.

27 27 ATP cycle ATP hydrolysis drives endergonic reactions –Coupled reaction results in net –ΔG (exergonic and spontaneous) ATP not suitable for long-term energy storage –Fats and carbohydrates better –Cells store only a few seconds worth of ATP

28 28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. + + PiPi Energy from exergonic cellular reactions ATP H2OH2O ADP Energy for endergonic cellular processes cell respiration photosynthesis

29 29 Enzymes: Biological Catalysts Most enzymes are protein –Some are RNA Shape of enzyme stabilizes a temporary association between substrates Enzyme not changed or consumed in reaction Carbonic anhydrase (enzyme used to maintain blood pH) –200 molecules of carbonic acid per hour made without enzyme –600,000 molecules formed per second with enzyme

30 30 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Active site a.b. EnzymeEnzyme–substrate complex Substrate

31 Active site Pockets or clefts for substrate binding Forms enzyme–substrate complex Precise fit of substrate into active site Applies stress to distort particular bond to lower activation energy –Induced fit 31

32 32 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. The substrate, sucrose, consists of glucose and fructose bonded together. 2. The substrate binds to the active site of the enzyme, forming an enzyme– substrate complex. 3. The binding of the substrate and enzyme places stress on the glucose– fructose bond, and the bond breaks. 4. Products are released, and the enzyme is free to bind other substrates. Bond Glucose Fructose Active site Enzyme sucrase H2OH2O

33 33 Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

34 34 Nonprotein enzymes Ribozymes 1981 discovery that certain reactions catalyzed in cells by RNA molecule itself 1. 2 kinds 1.Intramolecular catalysis – catalyze reaction on RNA molecule itself 2.Intermolecular catalysis – RNA acts on another molecule

35 Enzyme function Small molecules can affect function –Coenzymes –Cofactors Rate of enzyme-catalyzed reaction depends on concentrations of substrate and enzyme Any chemical or physical condition that affects the enzyme’s three-dimensional shape can change rate 35

36 36 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. Rate of Reaction Optimum pH for pepsin Rate of Reaction pH of Reaction Optimum pH for trypsin Temperature of Reaction (˚C) Optimum temperature for human enzyme Optimum temperature for enzyme from hotsprings prokaryote

37 37 Inhibitors Inhibitor – substance that binds to enzyme and decreases its activity Competitive inhibitor –Competes with substrate for active site Noncompetitive inhibitor –Binds to enzyme at a site other than active site –Causes shape change that makes enzyme unable to bind substrate

38 38 a. Competitive inhibitionb. Noncompetitive inhibition Enzyme Allosteric site Active site Competitive inhibitor interferes with active site of enzyme so substrate cannot bind Allosteric inhibitor changes shape of enzyme so it cannot bind to substrate Active site Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Substrate Inhibitor

39 39 Allosteric Enzymes Allosteric enzymes – enzymes exist in active and inactive forms Most noncompetitive inhibitors bind to allosteric site – chemical on/off switch Allosteric inhibitor – binds to allosteric site and reduces enzyme activity Allosteric activator – binds to allosteric site and increases enzyme activity

40 Question If inhibition is to be competitive, which of the following must be true? a.There must be more than one binding site b.The substrate and the inhibitor must be similar c.The reaction can not require a cofactor d.The reaction must be endergonic e.The allosteric and active sites must be near each other

41 Question Carbon monoxide (CO) binds to the hemoglobin protein at the oxygen binding site. Once the CO binds, the oxygen can no longer be transported. What does this describe? a.Non-competitive inhibition b.Feedback inhibition c.Substrate inhibition d.Allosteric inhibition e.Competitive inhibition

42 Question Increasing the temperature increases the rate of an enzyme-catalyzed reaction. Once a critical temperature is reached, the reaction stops. Why does this happen? a.The concentration of reactants drop b.The enzymes have all been consumed in the reaction c.The increase in temperature alters the pH d.The polypeptide chains in the enzyme denature

43 Section 6.5 Learning Objectives –Metabolism: The Chemical Description of Cell Function Explain the kinds of reactions that make up metabolism. Discuss what is meant by a metabolic pathway. Describe mechanisms to control a metabolic pathway 43

44 44 Metabolism Total of all chemical reactions carried out by an organism Anabolic reactions/anabolism –Expend energy to build up molecules –Anabolic Steroids=build muscle Catabolic reactions/catabolism –Harvest energy by breaking down molecules –Starvation=breakdown muscle Large molecules Small molecules

45 45 Biochemical pathways Chemical reactions that create/store or produce other chemical products for daily function. Reactions occur in a sequence Product of one reaction is the substrate for the next reaction Enzyme 1Enzyme 2Enzyme 3 ABCD

46 Basic metabolic pathway chart 46

47 47 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Initial substrate Intermediate substrate A Intermediate substrate B Intermediate substrate C End product Enzyme1 Enzyme2 Enzyme3 Enzyme4

48 Feedback inhibition End-product of pathway binds to an allosteric site on enzyme that catalyzes first reaction in pathway Shuts down pathway so raw materials and energy are not wasted 48

49 49 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a.b. Enzyme 1 Enzyme 2 Enzyme 3 Enzyme 1 Enzyme 2 Enzyme 3 End product Initial substrate Intermediate substrate A Intermediate substrate B Initial substrate

50 50 Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

51 Question Feedback inhibition occurs when the final product acts as an inhibitor to the first enzyme in the pathway. a.This is true b.This is false

52 Question Catabolic reactions expend energy to form or transform chemical bonds. a.This is true b.This is false

53 Final Review 53

54 Question The First Law of Thermodynamics states that energy can be – a.Created b.Destroyed c.Converted d.Lost e.None of the above

55 Question Small organic molecules that assist in enzymatic functions are – a.Coprolites b.Cofactors c.Activators d.Coenzymes e.Intermediates

56 Question Spending ATP involves hydrolyzing it into ADP and inorganic P. The energy released can drive other chemical reactions. a.This is true b.This is false

57 Question Enzymes are consumed by reactions. a.This is true b.This is false

58 Question A catalyst speeds up chemical reactions. How do catalysts do this? a.Decreasing entropy b.Altering ∆G c.Consuming reactants d.Lowering activation energy e.Making different products

59 Question A muscle contraction is ________, but as the muscle contracts heat is released which is ___________. a.Exergonic, endergonic b.Exergonic, exergonic c.Endergonic, endergonic d.Endergonic, exergonic

60 Question Study this metabolic pathway: A -E 1  B -E 2  C -E 3  D. Which of the following statements is NOT correct? (E represents enzymes) a.C is the substrate for enzyme E 1 and D is the product b.A is the substrate for enzyme E 1 and B is the product c.Enzyme E 2 can catalyze the substrate B but not A, C and D d.B is the product formed by enzyme E 1 but the substrate for enzyme E 2

61 Question When muscles contract, chemical energy is converted to mechanical energy with the loss of heat. This conversion of energy is an example of the ______ Law of Thermodynamics. a.First b.Second c.Third d.Fourth

62 Question Which of the following is defined as the amount of heat required to raise one gram of water one degree Celsius? a.Tesla b.Joule c.Newton d.Calorie e.calorie


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