1. Chapter 9 Introduction to Metabolism

2. An Overview of Metabolism Metabolism is the total of all chemical reactions in the cell and is divided into two parts catabolism – energy-conserving reactions that also generate a ready supply of electrons (reducing power) and precursors for biosynthesis E.g break down of glucose to release energy in the form of ATP in the mitochondria. anabolism – the synthesis of complex organic molecules from simpler ones e.g formation of starch from carbondioxide

3. Anabolism Anabolism are reaction which requires energy E.g Photosynthesis in chloroplast Catabolism are reaction where energy is released E,g Cellular respiration in mitochondria

4. Energy and Work Energy is defined as the capacity to do work or to cause particular changes

5. Types of Work Carried out by Organisms Chemical work Synthesis of complex molecules from simpler precursors (i.e anabolism). Here energy is needed to increase the complexity of a cell. Transport work Take up of nutrients, elimination of wastes, and maintenance of ion balances i.e energy is needed to transport molecules and ions across a cell membrane against a gradient. Mechanical work Energy is needed for cell motility and movement of structures within cells

6. The Laws of Thermodynamics To understand how energy is conserved in ATP and how ATP is used to do work in a cell, one has to understand the law of Thermodyanamics. Thermodynamics a science that analyzes energy changes in a collection of matter called a system (e.g., a cell or a plant) all other matter in the universe is called the surroundings

7. ….The Laws of Thermodynamics Thermodynamics focuses on the energy difference between the initial state and final state of a system and not the rate of the process from one state to another e.g boiling of water: cold liquid–hot-vapor i.e energy moves from one state to another ( thermodyanmics is not concerned with the rate at which the water is boiling.

8. First Law of Thermodynamics Two laws of Thermodynamics: First Law: energy can be neither created nor destroyed total energy in universe remains constant however, energy may be redistributed either within a system or between the system and its surroundings

9. ..First Law of Thermodynamics Example in some reaction energy is released and in some it is absorbed..Why? We need the second Law of Dynamics to explain why?

10. Second Law of Thermodynamics Entropy is a condition of matter and the amount of randomness (disorder) in a system The second law of Thermodynamics state that physical and chemical processes proceed in such a way that the disorder of the universe ( the system and its surroundings) increases to the maximum possible. The greater the disorder the greater is the entropy of the universe, however, the entropy of a system varies: increases, decreases or remain constant.

11. Energy Units calorie (cal) amount of heat energy needed to raise 1 gram of water from 14.5 to 15.5°C joules (J)-amount of energy can also be expressed in joules units of work capable of being done 1 cal of heat is equivalent to 4.1840 J of work Refer pg 170 for Kilo joule and Kilo calorie

12. Free Energy and Reactions The first and Second Law of Thermodynamics can be combined as follows: Free energy change,  G =  H - T  S to expresse the change in energy that can occur in chemical reactions and other processes to indicate if a reaction will proceed spontaneously Where,

13.  G =  H - T  S  G free energy change amount of energy that is available to do work at constant temperature and pressure  H change in enthalpy (heat content)/change in the total energy during the reaction T temperature in Kelvin ( 0 C +273)  S change in entropy occurring during the reaction ( entropy is randomness/disorder)

14. Chemical Equilibrium The change in the free energy has a definite and concrete relationship to the direction of chemical reactions. Equilibrium: consider the chemical reaction A + B ↔ C + D reaction is at equilibrium when rate of forward reaction = rate of reverse reaction Equilibrium constant (K eq ) expresses the equilibrium concentrations of products and reactants to one another. No further changes occur in the products or reactants

15. Chemical Equilibrium Equilibrium Constant: (K eq ) = (C) (D)/(A)(B) The equilibrium constant (K eq ) of a reaction is directly related to its change in free energy.

16. Standard Free Energy Change (  Gº) Standard Free Energy Change is when free energy change is determined at standard conditions of concentration, pressure, temperature, and pH  Gº symbol used to indicate standard free energy change at pH 7 (close to pH of living cells) and is directly related to K eq (equilibrium constant) Relationship between  Gº & K eq :  Gº´ = -2.303RTlogK eq Where, R is the gas constant(1.9872 cal/mole-degree) 7 T is absolute temperature

17. Types of energy driven reactions Exergonic reaction- reactions in a cell when energy is released from energy source and standard free energy change (  G ´ ) is negative & Equilibrium constant (K eq) is greater than one. Endergonic reactions-reactions in a cell when energy is trapped and the energy captured by cell is used to drive reactions to completion, hence standard free energy change (  G ´ ) is positive & (K eq) is less than one.

18. The Relationship… Figure 9.1 Relationship between Equilibrium constant and Free Energy Change.

19. Assignment on Adenosine 5’ triphosphate (ATP) (SL.19-27) for next lecture!! Adenosine 5’ triphosphate For all metabolic reactions (exergonic & endergonic) energy in the form of ATP drives the processes in a cell Some reactions earn ATP and some process spend ATP ATP serves as a link between exergonic & endergonic reactions ATP also referred as Energy Currency of the Cell.

20. ..Role of ATP in Metabolism Endergonic e;g reactant (A+b) to give product (C+D) Exergonic breakdown of ATP to ADP is aiding an endergonic reactions to make them more favorable Figure 9.3 ATP as a coupling agent

21. ..Adenosine-5'-triphosphate (ATP) Adenosine-5'-triphosphate (ATP) is a multifunctional nucleotide "molecular unit of currency" of intracellular energy transfer In this role, ATP transports chemical energy

22. ….Adenosine-5'-triphosphate (ATP) ATP is made from adenosine diphospahate (ADP) or adenosine monophosphate (AMP), and its use in metabolism converts it back into these precursors. ATP is therefore continuously recycled in organisms, with the human body turning over its own weight in ATP each day

23. ..Adenosine-5'-triphosphate This conversion of ATP to ADP is an extremely crucial reaction for the supplying of energy for life processes. Just the breaking of one bond with the accompanying rearrangement is sufficient to liberate about 7.3 kilocalories per mole = 30.6 kJ/mol. This is about the same as the energy in a single peanut!!

24. Adenosine-5'-triphosphate Living things can use ATP like a battery. The ATP can power needed reactions by losing one of its phosphorous groups to form ADP One can use food energy (cellular respiration) in the mitochondria to convert the ADP back to ATP so that the energy is again available to do needed work In plants, sunlight energy can be used to convert the less active compound (CO2) and water back to the highly energetic form ( to starch )

25. ..Structure of Adenosine 5’-triphosphate (ATP) Energy Currency of the Cell Figure 9.2- Pyrimidine ring with carbon atoms in a ribose attached to 3 phosphate group, adenine and an amino group.

26. ..Adenosine 5’ triphosphate Structure of ATP has a carbon compound as a backbone Part which is really critical is the phosphorous part - the triphosphate. Three phosphorous groups are connected by oxygens to each other, and there are also side oxygens connected to the phosphorous atoms. Each of these oxygens has a negative charge & the negative charges repel each other.Highly charged These bunched up negative charges, want to escape - to get away from each other, so there is a lot of potential energy here.

27. The Cell’s Energy Cycle Figure 9.4 Cell Energy Cycle

28. Oxidation-Reduction Reactions and Electron Carriers many metabolic processes involve oxidation-reduction reactions (electron transfers) electron carriers are often used to transfer electrons from an electron donor to an electron acceptor

29. Oxidation-Reduction (Redox) Reactions can result in energy release, which can be conserved and used to form ATP E.g Acceptor + e - =donor The acceptor and the donor makes a couple and called a redox couple In a reversible reaction, the acceptor becomes the donor until an equilibrium is reached called Standard Reduction Potential (E 0 )

30. ..REDOX The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms: The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms: Oxidation describes the loss of electrons / hydrogen or gain of oxygen Oxidation describes the loss of electrons / hydrogen or gain of oxygenelectrons hydrogenoxygenelectrons hydrogenoxygen Reduction describes the gain of electrons / hydrogen or a loss of oxygen Reduction describes the gain of electrons / hydrogen or a loss of oxygenelectrons hydrogenoxygenelectrons hydrogenoxygen

31. …Redox This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane (CH 4 ), the reduction of carbon by hydrogen to yield methane (CH 4 ), or it can be a complex process such as the oxidation of sugar in the human body through a series of very complex electron transfer processes. or it can be a complex process such as the oxidation of sugar in the human body through a series of very complex electron transfer processes.

32. Standard Reduction Potential (E 0 ) Equilibrium constant for an oxidation- reduction reaction and is measured in volts (unit of electric potential) Hence redox couples are a potential source of energy A measure of the tendency of the reducing agent to lose electrons Redox couple with more negative E 0 (Std reduction potential)  better electron donor i.e reducing agent has tendency to lose more electrons Redox couple with more positive E 0 (Std reduction potential)  better electron acceptor

33. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 33 Electron Transport Chains (ETC) Also known as electron transport system (ETS) Also known as electron transport system (ETS) ETC comprises of electron carriers such as co-enzymes, NAD ( Nicotinamide adenine dinucleotide), or FAD (Flavin adenine dinucleotide) and others ETC comprises of electron carriers such as co-enzymes, NAD ( Nicotinamide adenine dinucleotide), or FAD (Flavin adenine dinucleotide) and others E.g when glucose ( C 6 H 12 O 6 ) is oxidised during cellular respiration, many electrons are released and these are accepted by NAD which is converted/reduced to NADH E.g when glucose ( C 6 H 12 O 6 ) is oxidised during cellular respiration, many electrons are released and these are accepted by NAD which is converted/reduced to NADH

34. ..ETC During Cellular Respiration: During Cellular Respiration: C 6 H 12 O 6 + 6O 2 ––> 6CO 2 + 6H 2 O + energy ATP), C 6 H 12 O 6 + 6O 2 ––> 6CO 2 + 6H 2 O + energy ATP), NADH transfers electrons to Oxygen via a series of electron carriers with varying redox potential (which is organised into a system called electron transport system. NADH transfers electrons to Oxygen via a series of electron carriers with varying redox potential (E 0) which is organised into a system called electron transport system.

35. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 35 Electron Carriers NAD NAD nicotinamide adenine dinucleotide nicotinamide adenine dinucleotide NADP NADP nicotinamide adenine dinucleotide phosphate nicotinamide adenine dinucleotide phosphate

36. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 36 …Electron Carriers FAD FAD flavin adenine dinucleotide flavin adenine dinucleotide FMN FMN flavin mononucleotide flavin mononucleotide Figure 9.8

37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 37 …Electron Carriers cytochromes cytochromes use iron to transfer electrons use iron to transfer electrons iron is part of a heme group iron is part of a heme group

38. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 38 …Electron Carriers coenzyme Q (CoQ) coenzyme Q (CoQ) a quinone a quinone also called ubiquinone also called ubiquinone Figure 9.9

39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 39 …Electron Carriers nonheme iron proteins nonheme iron proteins e.g., ferredoxin e.g., ferredoxin use iron to transport electrons use iron to transport electrons

40. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 40 Enzymes Enzymes are critically important for cells to speed up reactions. They act as catalysts Enzymes are critically important for cells to speed up reactions. They act as catalysts catalyst catalyst substance that increases the rate of a reaction without being permanently altered substance that increases the rate of a reaction without being permanently altered substrates substrates reacting molecules reacting molecules products products substances formed by reaction substances formed by reaction

41. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 41 Enzyme Structure Many enzymes are composed of only proteins. However many enzymes are composed an Apoenzyme which is protein component of an enzyme and a protein component of an enzyme and aCofactor nonprotein component of an enzyme nonprotein component of an enzyme prosthetic group – firmly attached prosthetic group – firmly attached coenzyme – loosely attached coenzyme – loosely attached Holoenzyme is a complete enzyme i.e Holoenzyme= apoenzyme + cofactor Holoenzyme is a complete enzyme i.e Holoenzyme= apoenzyme + cofactor

42. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 42Coenzymes Coenzymes often act as carriers, transporting substances around the cell Coenzymes often act as carriers, transporting substances around the cell Figure 9.11- Coenzyme as a carrier

43. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 43 The Mechanism of Enzyme Reactions a typical exergonic reaction A + B  AB ‡  C + D transition-state complex – resembles both the substrates and the products

44. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 44 Activation energy (E a) – energy required to form transition-state complex Activation energy (E a) – energy required to form transition-state complex enzyme speeds up reaction by lowering E a enzyme speeds up reaction by lowering E a

45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 45 How Enzymes Lower A ctivation energy ( E a) by increasing concentrations of substrates at active site of enzyme by increasing concentrations of substrates at active site of enzyme by orienting substrates properly with respect to each other in order to form the transition-state complex by orienting substrates properly with respect to each other in order to form the transition-state complex

46. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 46 Lock and Key Model of Enzyme Function Figure 9.13 Lock and Key Model of Enzyme Function

47. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 47 The Effect of Environment on Enzyme Activity Rate of enzyme activity is significantly impacted by substrate concentration, pH, and temperature Rate of enzyme activity is significantly impacted by substrate concentration, pH, and temperature

48. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 48 Effect of [substrate] rate increases as [substrate] increases rate increases as [substrate] increases no further increase occurs after all enzyme molecules are saturated with substrate no further increase occurs after all enzyme molecules are saturated with substrate Figure 9.15

49. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 49 Effect of pH and Temperature Each enzyme has specific pH and temperature optima Each enzyme has specific pH and temperature optima Denaturation Denaturation loss of enzyme’s structure and activity when temperature and pH rise too much above optima loss of enzyme’s structure and activity when temperature and pH rise too much above optima

50. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 50 Enzyme Inhibition Competitive inhibitor Microorganisms can be poisoned with enzyme inhibitors / competitive inhibitor which directly competes with binding of substrate to active site Noncompetitive inhibitor –binds enzyme at site other than active site; changes enzyme’s shape so that it becomes less active

51. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 51 Metabolic Channeling Metabolic Channeling-differential localization of enzymes and metabolites Metabolic Channeling-differential localization of enzymes and metabolites compartmentation compartmentation differential distribution of enzymes and metabolites among separate cell structures or organelles differential distribution of enzymes and metabolites among separate cell structures or organelles

52. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 52 Chemotaxis An example of a complex behavior that is regulated by altering enzyme activity An example of a complex behavior that is regulated by altering enzyme activity system involves a number of enzymes and other proteins that are regulated by covalent modification e.g Chemotaxis response of E. coli system involves a number of enzymes and other proteins that are regulated by covalent modification e.g Chemotaxis response of E. coli

53. Bibliography Lecture PowerPoints Prescott’s Principles of Microbiology-Mc Graw Hill Co. Lecture PowerPoints Prescott’s Principles of Microbiology-Mc Graw Hill Co. http://en.wikipedia.org/wiki/Scientific_metho d http://en.wikipedia.org/wiki/Scientific_metho d http://en.wikipedia.org/wiki/Scientific_metho d http://en.wikipedia.org/wiki/Scientific_metho d https://files.kennesaw.edu/faculty/jhendrix/bi o3340/home.html https://files.kennesaw.edu/faculty/jhendrix/bi o3340/home.html https://files.kennesaw.edu/faculty/jhendrix/bi o3340/home.html https://files.kennesaw.edu/faculty/jhendrix/bi o3340/home.html http://hyperphysics.phy- astr.gsu.edu/Hbase/biology/atp.html http://hyperphysics.phy- astr.gsu.edu/Hbase/biology/atp.html http://hyperphysics.phy- astr.gsu.edu/Hbase/biology/atp.html http://hyperphysics.phy- astr.gsu.edu/Hbase/biology/atp.html