Intro to Metabolism Campbell Chapter 8

1. Intro to MetabolismCampbell Chapter 8 http://www.gifs.net http://ag.ansc.purdue.edu/sheep/ansc442/Semprojs/2003/spiderlamb/eatsheep.gif

2. Metabolism is the sum of an organism’s chemical reactions • Metabolism is an emergent property of life that arises from interactions between molecules within the cell http://www.encognitive.com/images/metabolic-pathways.png

3. A metabolic pathway begins with a specific molecule and ends with a product • Each step is catalyzed by a specific enzyme BIOCHEMICAL PATHWAYVIDEO

4. ENZYMES THAT WORK TOGETHER IN A PATHWAY CAN BE Concentrated in specific location Covalently bound incomplex Soluble with free floating intermediates Attached toa membranein sequence Biochemistry Lehninger

5. CATABOLIC PATHWAY (CATABOLISM)Release of energy by the breakdown of complex molecules to simpler compoundsEX: digestive enzymes break down food ANABOLIC PATHWAY (ANABOLISM)consumes energy to build complicated molecules from simpler onesEX: linking amino acids to form proteins http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/nanoscience/sci_media/images/chemical_reactions_involve_making_new_combinations/53823-2-eng-NZ/chemical_reactions_involve_making_new_combinations_full_size_landscape.jpg

6. Forms of Energy • ENERGY = capacity to cause change • Energy exists in various forms (some of which can perform work) • Energy can be converted from one form to another

7. KINETICENERGY – energy associated with motion • HEAT (thermal energy) is kinetic energy associated with random movement of atoms or molecules POTENTIALENERGY = energy that matter possesses because of its location or structure • CHEMICAL energy is potential energy available for release in a chemical reaction

8. Diving converts potential energy to kinetic energy. On the platform, the diver has more potential energy. In the water, the diver hasless potential energy. Climbing up converts kinetic energy of muscle movement to potential energy.

9. THERMODYNAMICS = the study of energy transformations • CLOSED system (EX: liquid in a thermos) = isolated from its surroundings • OPEN system energy + matter can be transferred between the system and its surroundings • Organisms are open systems http://ag.ansc.purdue.edu/sheep/ansc442/Semprojs/2003/spiderlamb/eatsheep.gif

10. The First Law of Thermodynamics = energy of the universe is constant • Energy can be transferred and transformed • Energy cannot be created or destroyed • The first law is also called the principle of CONSERVATION OF ENERGY http://www.pxleyes.com/photoshop-picture/4a3b747566555/remote-control.htmlhttp://www.suncowboy.com/solar101.php

11. The Second Law of Thermodynamics During every energy transfer or transformation • entropy (disorder) of the universe INCREASES • some energy is unusable, often lost as heat http://hyperphysics.phy-astr.gsu.edu/hbase/therm/entrop.html http://www.janebluestein.com/articles/whatswrong.html

12. Second law of thermodynamics First law of thermodynamics Chemical energy Heat CO2 H2O ORGANISMS are energy TRANSFORMERS! Spontaneous processes occur without energy input; they can happen quickly or slowly For a process to occur without energy input, it must increase the entropy of the universe

13. Free-Energy Change (G) can help tell which reactions will happen ∆G = change in free energy ∆H = change in total energy (enthalpy) or change ∆S = entropy T = temperature ∆G = ∆H - T∆S • Only processes with a negative ∆G are spontaneous • Spontaneous processes can be harnessed to perform work

14. Exergonic and Endergonic Reactions in Metabolism • EXERGONIC reactions (- ∆G) • Release energy • are spontaneous ENDERGONIC reactions (+ ∆G) • Absorb energy fromtheir surroundings • are non-spontaneous

15. Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions • A cell does three main kinds of work: • Mechanical • Transport • Chemical • 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

16. ATP (adenosine triphosphate) is the cell’s renewable and reusable energy shuttle ATP provides energy for cellular functions Energy to charge ATP comes from catabolic reactions Adenine Phosphate groups Ribose

17. LE 8-9 P P P Adenosine triphosphate (ATP) H2O + P P P + Energy i Adenosine diphosphate (ADP) Inorganic phosphate

18. ATP Energy for cellular work provided by the loss ofphosphate from ATP Energy from catabolism (used to charge upADP into ATP ADP + P i

19. Endergonic reaction: DG is positive, reaction is not spontaneous NH2 NH3 DG = +3.4 kcal/mol + Glu Glu Ammonia Glutamine Glutamic acid Exergonic reaction: DG is negative, reaction is spontaneous P ATP ADP DG = –7.3 kcal/mol H2O + + i Coupled reactions: Overall DG is negative; Together, reactions are spontaneous DG = –3.9 kcal/mol

20. LE 8-11 P i P Protein moved Motor protein Mechanical work: ATP phosphorylates motor proteins Membrane protein ADP ATP + P i P P i Solute transported Solute Transport work: ATP phosphorylates transport proteins P NH2 NH3 P + + Glu i Glu Reactants: Glutamic acid and ammonia Product (glutamine) made Chemical work: ATP phosphorylates key reactants

21. Every chemical reaction between molecules involves bond breaking and bond forming ACTIVATION ENERGY = amount of energy required to get chemical reaction started Activation energy is often supplied in the form of heat from the surroundings Free energy animation IT’S LIKE PUSHING A SNOWBALL UP A HILL . . . Once you get it up there, it can roll down by itself http://www.chuckwagondiner.com/art/matches.jpg http://plato.acadiau.ca/COURSES/comm/g5/Fire_Animation.gif

22. The Activation Energy Barrier LE 8-14 B A C D Transition state EA B A Free energy D C Reactants B A DG < O C D Products Progress of the reaction

23. CATALYST = a chemical agent that speeds up a reaction without being consumed by the reaction ENZYMES = biological catalystsMost enzymes are PROTEINS Exception = ribozymes (RNA) Ch 17 & 26

24. Course of reaction without enzyme EA without enzyme EA with enzyme is lower Reactants Free energy Course of reaction with enzyme DG is unaffected by enzyme Products Progress of the reaction ENZYMES work by LOWERING ACTIVATION ENERGY;

25. ENZYMES LOWER ACTIVATION ENERGY BY • Orienting substrates correctly • Straining substrate bonds • Providing a favorable microenvironment Enzymes change ACTIVATION ENERGY but NOT energy of REACTANTS or PRODUCTS http://sarahssureshots.wikispaces.com/Focus+on+Proteins http://www.ac-montpellier.fr/sections/personnelsen/ressources-pedagogiques/education-artistique/consultation-avis-du

26. ENZYMES • Most are proteins • Lower activation energy • Specific • Shape determines function • Reusuable • Unchanged by reaction Image from: http://www.hillstrath.on.ca/moffatt/bio3a/digestive/enzanim.htm

27. The REACTANT that an enzyme acts on = SUBSTRATE • Enzyme + substrate =ENZYME-SUBSTRATE COMPLEX • Region on the enzyme where the substrate binds = ACTIVE SITE • Substrate held in active site by WEAK interactions (ie. hydrogen and ionic bonds)

28. TWO MODELS PROPOSED • LOCK & KEYActive site on enzymefits substrate exactly • INDUCED FITBinding of substrate causes changein active site so it fits substratemore closely http://www.grand-illusions.com/images/articles/toyshop/trick_lock/mainimage.jpg http://commons.wikimedia.org/wiki/File:Induced_fit_diagram.png

29. Enzyme Activity can be affected by: • General environmental factors, such as temperature, pH, salt concentration, etc. • Chemicals that specifically influence the enzyme See a movie Choose narrated http://www.desktopfotos.de/Downloads/melt_cd.jpg http://www.nealbrownstudio.com/adm/photo/163_nb_fried_egg.jpg

30. TEMPERATURE & ENZYME ACTIVITY Each enzyme has an optimal temperature at which it can function (Usually near body temp) http://www.animated-gifs.eu/meteo-thermometers/001.htm

31. http://www.uic.edu/classes/bios/bios100/lectures/chemistry.htmhttp://www.uic.edu/classes/bios/bios100/lectures/chemistry.htm Increasing temperature increases the rate of an enzyme-catalyzed reaction up to a point. Above a certain temperature, activity begins to decline because the enzyme begins to denature.

32. pH and ENZYME ACTIVITYEach enzyme has an optimal pH at which it can function

33. http://www.wissensdrang.com/media/wis9r.gif COFACTORS= non-protein enzyme helpers • EX: Zinc, iron, copper COENZYMES= organic enzyme helpers • Ex: vitamins http://www.elmhurst.edu/~chm/vchembook/595FADcoq.html

34. SUBSTRATE CONCENTRATION & ENZYME ACTIVITY ← V MAX Adding substrate increases activity up to a point

35. REGULATION OF ENZYME PATHWAYS • GENE REGULATIONcell switches on or off the genes that code for specific enzymes

36. REGULATION OF ENZYME PATHWAYS • FEEDBACK INHIBITIONend product of a pathway interacts with and “turns off” an enzyme earlier in pathway • prevents a cell from wasting chemical resources by synthesizing more product than is needed FEEDBACK INHIBITION

37. A A Negative feedback Enzyme 1 Enzyme 1 B B Enzyme 2 C C Enzyme 3 D D D D D D D D D D D NEGATIVE FEEDBACK • An accumulation of an end product slows the process that produces that product Example: sugar breakdown generates ATP; excess ATP inhibits an enzyme near the beginning of the pathway

38. W W Enzyme 4 Enzyme 4 Positivefeedback X X Enzyme 5 Enzyme 5 Y Y Enzyme 6 Enzyme 6 Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z POSITIVE FEEDBACK (less common) • The end product speeds up production EXAMPLE: Chemicals released by platelets that accumulate at injury site, attract MORE platelets to the site.

39. REGULATION OF ENZYME ACTIVITY • ALLOSTERIC REGULATIONprotein’s function at one site is affected by binding of a regulatory molecule at another site • Allosteric regulation can inhibit or stimulate an enzyme’s activity Allosteric enzyme inhibition http://bio.winona.edu/berg/ANIMTNS/allostan.gif

40. SOME ALLOSTERIC ENZYMES HAVE MULTIPLE SUBUNITS • Each enzyme has active and inactive forms • The binding of an ACTIVATOR stabilizes the active form • The binding of an INHIBITOR stabilizes the inactive form

41. Binding of one substrate molecule to active site of one subunit locks all subunits in active conformation. Substrate Inactive form Stabilized active form Cooperativity another type of allosteric activation

42. COOPERATIVITY= form of allosteric regulation that can amplify enzyme activity Binding of one substrate to active site of one subunit locks all subunits in active conformation

43. Enzyme Inhibitors COMPETITIVE inhibitor REVERSIBLE; Mimics substrate and competes with substrate for active site on enzyme ENZYMEANIMATION

44. Enzyme Inhibitors NONCOMPETITIVE inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective ENZYMEANIMATION