Chapter 7 - Enzymes, Metabolism and Cellular Respiration

Chapter 7 - Enzymes, Metabolism and Cellular Respiration -...

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Click to edit Master subtitle style 4/30/11 ENZYMES,METABOLISM,AND CELLULAR RESPIRATION CHAPTER 7
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4/30/11 Metabolism Sum total of all chemical reactions that occur within an organism Also refers to specific chemical reactions at the cellular level n 2 factors govern fate of a chemical reaction Direction § Many cells use ATP to drive reactions in 1 direction Rate § Catalysts called enzyme can speed the reaction rate aA + bB ↔ cC + dD Chemical reactions
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4/30/11 Energy Ability to promote change 2 forms Kinetic- associated with movement Potential- due to structure or location Chemical energy- energy in molecular bonds
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4/30/11 2 Laws of thermodynamics 1. First law n Law of conservation of energy n Energy cannot be created or destroyed 2. Second law n Transfer or transformation of energy from one form to another increases entropy or degree of disorder of a system
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4/30/11 Change in free energy determines direction Energy transformations involve an increase in entropy Entropy - a measure of the disorder that cannot be harnessed to do work n H= enthalpy or total energy n G= free energy or amount of energy for work n S= entropy or unusable energy n T= absolute temperature in Kelvin (K) H = G + TS
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4/30/11 Spontaneous reactions? Occur without input of additional energy Not necessarily fast Key factor is the free energy change ΔG = Δ H - T Δ S n Exergonic ΔG < 0 or negative free energy change Spontaneous n Endergonic ΔG > 0 or positive free energy change Requires addition of free energy Not spontaneous
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4/30/11 Hydrolysis of ATP ΔG = -7.3 kcal/mole Reaction favors formation of products Energy liberated can drive a variety of cellular processes Cells use ATP hydrolysis An endergonic reaction can be coupled to an exergonic reaction Endergonic reaction will be spontaneous if net free energy change for both processes is negative ATP
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4/30/11 Glucose + phosphate → glucose-phosphate + H2O ΔG = +3.3 Kcal/mole endergonic ATP + H2O → ADP + Pi ΔG = -7.3 Kcal/mole exergonic Coupled reaction Glucose + ATP → glucose-phosphate + ADP ΔG = -4.0 Kcal/mole
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4/30/11 Enzymes A spontaneous reaction is not necessarily a fast reaction Catalyst- agent that speeds up the rate of a chemical reaction without being consumed during the reaction Enzymes- protein catalysts in living cells Activation energy n Initial input of energy to start reaction n Allows molecules to get close enough to cause bond rearrangement n Can now achieve transition state where bonds are stretched
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This note was uploaded on 04/29/2011 for the course CELL 101 taught by Professor Burdsal during the Fall '08 term at Tulane.

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Chapter 7 - Enzymes, Metabolism and Cellular Respiration -...

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