Fig. 8-2 Climbing up converts the kinetic energy of muscle movement to potential energy. A diver has less potential energy in the water than on the platform. Diving converts potential energy to kinetic energy. A diver has more potential energy on the platform than in the water.
Fig. 8-5 (a) Gravitational motion (b) Diffusion(c) Chemical reaction More free energy (higher G) Less stable Greater work capacity In a spontaneous change The free energy of the system decreases (G < 0) The system becomes more stable The released free energy can be harnessed to do work Less free energy (lower G) More stable Less work capacity
Fig. 8-5a Less free energy (lower G) More stable Less work capacity More free energy (higher G) Less stable Greater work capacity In a spontaneous change The free energy of the system decreases (G < 0) The system becomes more stable The released free energy can be harnessed to do work
Fig. 8-6 Reactants Energy Free energy Products Amount of energy released (G < 0) Progress of the reaction (a) Exergonic reaction: energy released Products Reactants Energy Free energy Amount of energy required (G > 0) (b) Endergonic reaction: energy required Progress of the reaction
Fig. 8-6a Energy (a) Exergonic reaction: energy released Progress of the reaction Free energy Products Amount of energy released (G < 0) Reactants
Fig. 8-6b Energy (b) Endergonic reaction: energy required Progress of the reaction Free energy Products Amount of energy required (G > 0) Reactants
Fig (b) Coupled with ATP hydrolysis, an exergonic reaction Ammonia displaces the phosphate group, forming glutamine. (a) Endergonic reaction (c) Overall free-energy change P P Glu NH 3 NH 2 Glu i ADP + P ATP + + Glu ATP phosphorylates glutamic acid, making the amino acid less stable. Glu NH 3 NH 2 Glu + Glutamic acid Glutamine Ammonia G = +3.4 kcal/mol + 2 1
Fig (b) Mechanical work: ATP binds noncovalently to motor proteins, then is hydrolyzed Membrane protein P i ADP + P Solute Solute transported P i VesicleCytoskeletal track Motor protein Protein moved (a) Transport work: ATP phosphorylates transport proteins ATP
Fig Substrates Enzyme Products are released. Products Substrates are converted to products. Active site can lower E A and speed up a reaction. Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. Substrates enter active site; enzyme changes shape such that its active site enfolds the substrates (induced fit). Active site is available for two new substrate molecules. Enzyme-substrate complex
Fig Rate of reaction Optimal temperature for enzyme of thermophilic (heat-tolerant) bacteria Optimal temperature for typical human enzyme (a) Optimal temperature for two enzymes (b) Optimal pH for two enzymes Rate of reaction Optimal pH for pepsin (stomach enzyme) Optimal pH for trypsin (intestinal enzyme) Temperature (ºC) pH
Fig Allosteric enyzme with four subunits Active site (one of four) Regulatory site (one of four) Active form Activator Stabilized active form Oscillation Non- functional active site Inhibitor Inactive form Stabilized inactive form (a) Allosteric activators and inhibitors Substrate Inactive form Stabilized active form (b) Cooperativity: another type of allosteric activation
Fig. 8-20a (a) Allosteric activators and inhibitors Inhibitor Non- functional active site Stabilized inactive form Inactive form Oscillation Activator Active formStabilized active form Regulatory site (one of four) Allosteric enzyme with four subunits Active site (one of four)
Fig RESULTS EXPERIMENT Caspase 1 Active site SH Known active form Substrate SH Active form can bind substrate SH Allosteric binding site Known inactive form Allosteric inhibitor Hypothesis: allosteric inhibitor locks enzyme in inactive form S–S Caspase 1 Active formAllosterically inhibited form Inhibitor Inactive form
Fig. 8-21a SH Substrate Hypothesis: allosteric inhibitor locks enzyme in inactive form Active form can bind substrate S–S SH Active site Caspase 1 Known active form Known inactive form Allosteric binding site Allosteric inhibitor EXPERIMENT
Fig. 8-21b Caspase 1 RESULTS Active form Inhibitor Allosterically inhibited form Inactive form
Fig Intermediate C Feedback inhibition Isoleucine used up by cell Enzyme 1 (threonine deaminase) End product (isoleucine) Enzyme 5 Intermediate D Intermediate B Intermediate A Enzyme 4 Enzyme 2 Enzyme 3 Initial substrate (threonine) Threonine in active site Active site available Active site of enzyme 1 no longer binds threonine; pathway is switched off. Isoleucine binds to allosteric site
Living Organisms and Order How do living organisms create macromolecules, organelles, cells, tissues, and complex higher-order structures? A The laws of thermodynamics do not apply to living organisms. B Living organisms create order by using energy from the sun. C Living organisms create order locally, but the energy transformations generate waste heat that increases the entropy of the universe.
Free Energy, Enthalpy, and Entropy When sodium chloride (table salt) crystals dissolve in water, the temperature of the solution decreases. This means that, for dissociation of Na + and Cl – ions, A the change in enthalpy (ΔH) is negative. B the change in enthalpy (ΔH) is positive, but the change in entropy is greater. C the reaction is endergonic, because it absorbs heat. D the reaction must be coupled to an exergonic reaction. E the reaction cannot occur spontaneously.
Life and Chemical Equilibrium Are chemical reactions at equilibrium in living cells? yes no only the exergonic reactions all reactions except those powered by ATP hydrolysis
Free Energy A reaction has a G of -5.6 kcal/mol. Which of the following would most likely be true? A The reaction could be coupled to power an endergonic reaction with a G of +8.8 kcal/mol. B The reaction would result in an increase in entropy (S) and a decrease in the energy content (H) of the system. C The reaction would result in products with a greater free-energy content than in the initial reactants.
Rate of a Chemical Reaction The oxidation of glucose to CO 2 and H 2 O is highly exergonic: ΔG = –636 kcal/mole. Why doesnt glucose spontaneously combust? A The glucose molecules lack the activation energy at room temperature. B There is too much CO 2 in the air. C CO 2 has higher energy than glucose. D The formation of six CO 2 molecules from one glucose molecule decreases entropy. E The water molecules quench the reaction.
Enzymes Firefly luciferase catalyzes the reaction luciferin + ATP adenyl-luciferin + pyrophosphate then the next reaction occurs spontaneously: adenyl-luciferin + O 2 oxyluciferin + H 2 O + CO 2 + AMP + light What is the role of luciferase? A Luciferase makes the ΔG of the reaction more negative. B Luciferase lowers the transition energy of the reaction. C Luciferase alters the equilibrium point of the reaction. D Luciferase makes the reaction irreversible. E all of the above
Enzyme-Catalyzed Reactions In the energy diagram below, which of the lettered energy changes would be the same in both the enzyme-catalyzed and uncatalyzed reactions? A B C D E
Enzyme Inhibitors Vioxx and other prescription non-steroidal anti- inflammatory drugs (NSAIDs) are potent inhibitors of the cycloxygenase-2 (COX-2) enzyme. High substrate concentrations reduce the efficacy of inhibition by these drugs. These drugs are A competitive inhibitors. B noncompetitive inhibitors. C allosteric regulators. D prosthetic groups. E feedback inhibitors.
Enzyme Regulation Adenosine monophosphate (AMP) activates the enzyme phosphofructokinase (PFK) by binding at a site distinct from the substrate binding site. This is an example of A cooperative activation. B allosteric activation. C activation by an enzyme cofactor. D coupling exergonic and endergonic reactions.