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Enzymes & Metabolism: Part 1 Unit 5

Enzymes & Metabolism: Part 1 Unit 5. Metabolism is the sum of an organism’s chemical reactions Metabolism arises from interactions between molecules within the cell. http://www.encognitive.com/images/metabolic-pathways.png.

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Enzymes & Metabolism: Part 1 Unit 5

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  1. Enzymes & Metabolism: Part 1 Unit 5

  2. Metabolism is the sum of an organism’s chemical reactions • Metabolism 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

  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 E.g.: Hydrolysis E.g.: Dehydration Synthesis 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. THERMODYNAMICS = the study of energy transformations • Organisms are open systems • OPEN system energy + matter can be transferred between the system and its surroundings http://ag.ansc.purdue.edu/sheep/ansc442/Semprojs/2003/spiderlamb/eatsheep.gif

  9. The First Law of Thermodynamics = energy of the universe is constant • Energy cannot be created or destroyed • CONSERVATION OF ENERGY http://www.pxleyes.com/photoshop-picture/4a3b747566555/remote-control.htmlhttp://www.suncowboy.com/solar101.php

  10. 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 (endotherms) http://hyperphysics.phy-astr.gsu.edu/hbase/therm/entrop.html http://www.janebluestein.com/articles/whatswrong.html

  11. 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

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

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

  14. ATP powers cellular work by coupling exergonic reactions to endergonic reactions • A cell does three main kinds of work: • Mechanical (cilia, muscle contractions) • Transport (movement of molecules) • Chemical (making polymers) • 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

  15. 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

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

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

  18. 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 hydrolysis Coupled reactions: Overall DG is negative; Together, reactions are spontaneous DG = –3.9 kcal/mol

  19. 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 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

  20. 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

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

  22. 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;

  23. 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

  24. 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

  25. 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)

  26. 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

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