Sept 8 - Biochem 423 Robert A Orlando Ph.D ENZYMES –...

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Biochem 423 Robert A. Orlando, Ph.D. ENZYMES – MECHANISM OF ACTION ‐‐ THERMODYNAMICS LIFE OCCURS BY CONVERTING: SUBSTRATE (S) → PRODUCT (P) BUT ALSO ← SO, Keq = [P] [S] DIRECTION OF REACTION DEPENDS ON ∆G (FREE ENERGY CHANGE BETWEEN SUBSTRATE AND PRODUCT) FOR A SPONTANEOUS REACTION: X ∆G = − RT ln Keq [P] [S] ∆G R = GAS CONSTANT = 8.315 J/MOL•K T = ABSOLUTE TEMP = 298 K 43 | P a g e LOTS OF [P] AND LITTLE [S] = HUGE − ∆G = SPONTANEOUS Biochem 423 Robert A. Orlando, Ph.D. REMINDER…. ∆G IS ACTUALLY ∆G’˚ NOW, SPONTANEOUS REACTIONS NEED NO HELP TO PROCEED….BUT WHAT ABOUT MORE COMPLEX REACTIONS, SUCH AS DESCRIBED BY: WHERE ∆G˚ FOR CHEMISTS = STANDARD FREE‐ENERGY CHANGE (T = 298K; GAS PRESSURE = 1 ATM; EACH SOLUTE = 1M) (ABOVE CONDITIONS + PH = 7.0) AND ∆G’˚ = BIOCHEMICAL STANDARD FREE‐ENERGY CHANGE ∆Gactivation ENZYMES = REDUCE ∆Gactivation EQUILIBRIUM NOT AFFECTED ∆G’˚ = − RT ln Keq 44 | P a g e Biochem 423 Robert A. Orlando, Ph.D. ENZYMES provide multi‐step reactions: E + S ↔ ES ↔ EP ↔ E + P 45 | P a g e Biochem 423 Robert A. Orlando, Ph.D. BINDING ENERGY OF SUBSTRATE TO ENZYME REDUCES FREE‐ENERGY ∆GB = BINDING ENERGY CONTRIBUTED BY: H‐BONDING IONIC INTERACTIONS HYDROPHOBIC 46 | P a g e Biochem 423 Robert A. Orlando, Ph.D. REMEMBER…. ∆G’˚ IS A CONSTANT (= − RT ln Keq) BECAUSE OF STANDARDIZED CONDITIONS PH 7.0 298K 1 ATM PRESSURE BUT CONCENTRATION OF REACTANTS IS ALMOST NEVER 1.0 M IN BIOLOGY…. EACH REACTANT AT 1.0 M CONCENTRATION ACTUAL FREE ENERGY CHANGE (∆G) MUST REFLECT THE TRUE STARTING CONCENTRATIONS OF THE REACTANTS: ∆G = ∆G’˚ + RT ln [P] [S] ∆G IS POSITIVE IF [P]>>>[S] ∆G IS NEGATIVE DEPENDS ON [S]>>>[P] FOR EXAMPLE [P]/[S] = 10 ln(10) = +2.3 [P]/[S] = 0.01 ln (0.01) = −4.6 47 | P a g e Biochem 423 Robert A. Orlando, Ph.D. ONE FINAL NOTE…. ∆G ARE ADDITIVE TO DETERMINE ∆G FOR ENTIRE REACTION GLUCOSE + Pi → GLUCOSE‐6‐PHOSPHATE + H2O ∆G’˚ = 13.8 KJ/MOL (UNDER STANDARD BIOCHEMICAL CONDITIONS) ATP + H2O → ADP + Pi ∆G’˚ = −30.5 KJ/MOL SUM OF REACTIONS: GLUCOSE + ATP → ADP + GLUCOSE‐6‐PHOSPHATE ∆G’˚ = 13.8 KJ/MOL + −30.5 KJ/MOL = −16.7 KJ/MOL EXERGONIC REACTION 48 | P a g e ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern