chapter 8 lecture notes

3 kcalmol g 73 kcalmol i key points atp

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Unformatted text preview: places phosphate group to form glutamine Coupled with ATP hydrolysis, it becomes an exergonic reac,on * Key Point: How ATP Drives Transport and Mechanical Work Transport Work: Direct Effect: Hydrolysis of ATP phosphorylates membrane protein Changes its shape and ohen its ability to bind another molecule (binding affinity) Example: Mechanical Work: Indirect Effect: ATP binds noncovalently to motor protein Hydrolysis of ATP changes the shape of the motor protein and allows it to interact with the cytoskeleton Example: The ATP Cycle: ATP is a renewable resource ATP synthesis from ADP and requires energy P ATP hydrolysis to ADP and i yields energy P ΔG = +7.3 kcal/mol ΔG =  ­7.3 kcal/mol i * * Key Points: * ATP cycle moves at an astonishing pace Example: Working muscle cell recycles its en,re pool of ATP in less than on minute Enzymes speed up metabolic reac1ons by lowering energy barriers Rate of a chemical reac,on is important * Example: Hydrolysis of Sucrose ΔG=  ­7 kcal/mol  ­ spontaneous Solu,on of sucrose will take years to break down If add enzyme, Sucrase, then the sucrose will be hydrolyzed in seconds Key Point: In this chapter we will focus on protein enzymes Ac1va1on Energy Barrier: ReacIon: AB + CD AC + BD Reac,on involves a transi,on state which is contorted and highly unstable Unstable Absorbing energy from surroundings * EA = Ac1va1on Energy  ­ΔG = indicates that the reac,on is spontaneous However, EA provides barrier that determines the rate of the reac,on * Enzymes Lower the EA Barrier Most of the macromolecules found in cells are high in free energy and have the poten,al to decompose spontaneously However they persist in cells because few molecules can make it over the hump of ac,va,on energy Why...
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