Bio Notes Chapter 7 - Chapter 7: Metabolism 1) Sum of an...

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Chapter 7: Metabolism 1) Sum of an organisms chemical reactions 2) Specific chemical reactions at the cellular level Glucose is stored (=potential energy) energy in chemical form Energy is “the ability to promote change” Reactions have a direction and a rate. aA + bB cC + dD a = concentration … A = substance This reaction can go in either direction, depending on energy and the reactants’ concentrations Total energy = usable energy and unusable energy. H = enthalpy or total energy G= free energy or usable energy for work T= absolute temperature in Kelvin (K) S= entropy or unusable energy H = G + TS ΔG = ΔH – TΔS Free energy change affects the direction of a reaction Exergonic: If ΔG<0, free energy is released and reaction is SPONTANEOUS Endergonic: If ΔG>0, free energy must be added and reaction is NOT SPONTANEOUS - ATP hydrolysis is very Exergonic (Fig 7.3) -Many biochemical reactions are endergonic. -Cells use ATP hydrolysis to drive endergonic How else do cells manipulate reaction rates? Enzymes (Fig 7.4) - Enzymes : proteins that catalyze reactions -Large size relative to the reactants. -Affected by changes in pH and temperature.
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Enzymes lower a reaction’s activation energy. (Fig 7.4) Binding in the active site may involve a conformational change. Strain the reactant’s bonds to lower activation energy. May temporarialy bond to one of the reactants. Substrate: reactants that bind to active site, forming the enzyme-substrate complex -Enzymes have a high affinity for their substrates Other molecules may be involved. -Prosthetic Groups (Permanently bound to enzyme)
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Bio Notes Chapter 7 - Chapter 7: Metabolism 1) Sum of an...

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