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Energy and Reactivity in Respiration Cascade Reactions

Explore the chemical reactions in the respiratory cascade, from Complex I to Proton-translocating ATPase, highlighting energy changes, electron transfer processes, and proton gradients in physical chemistry. Witness how molecules collide and react to facilitate cellular energy production.

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Energy and Reactivity in Respiration Cascade Reactions

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  1. Complex I ΔG°′ = –NFℰ°′ = –2 × 96485.3 C mol–1× 0.376 V = –72.6 kJ mol–1 Q ~ 1 CHEM 471: Physical Chemistry Vin – Vout ~ –160 mV ΔpH ~ 0.5 (Matrix pH 7.8; cytoplasmic pH 7.3) Δµ = ZFV + RT ln (cin/cout) = ZFV – 2.303RT ΔpH = –18.3 kJ mol–1

  2. The respiratory cascade CHEM 471: Physical Chemistry NAD+ + H+in + 2e– → NADHℰ°′ = –0.324 V UQ + 2H+in + 2e– → UQH2ℰ°′ = +0.052 V Reversing the first half-reaction, and adding, the overall reaction is strongly favorable UQ + H+in + NADH→ NAD+ + UQH2ℰ°′ = +0.376 V ΔG°′ = –NFℰ°′ = –2 × 96485.3 C mol–1× 0.376 V = –72.6 kJ mol–1

  3. Complex III UQ + 2H+in + 2e– → UQH2ℰ°′ = +0.052 V cyt-c(Fe3+) + e– → cyt-c(Fe2+)ℰ°′ = +0.254 V CHEM 471: Physical Chemistry 2 cyt-c(Fe3+) + UQH2→ 2 cyt-c(Fe2+) + UQ + 2 H+outℰ°′ = +0.202 V ΔG°′ = –NFℰ°′ = –2 × 96485.3 C mol–1× 0.202 V = –39.0 kJ mol–1

  4. Complex IV cyt-c(Fe3+) + e– → cyt-c(Fe2+)ℰ°′ = +0.254 V ½O2 + 2H+ + 2e– → H2Oℰ°′ = +0.815 V CHEM 471: Physical Chemistry ½O2 + 2H+ + 2 cyt-c(Fe2+) → H2O + 2 cyt-c(Fe3+)ℰ°′ = +0.561 V ΔG°′ = –NFℰ°′ = –2 × 96485.3 C mol–1× 0.561 V = –109.3 kJ mol–1

  5. Proton translocating ATPase CHEM 471: Physical Chemistry

  6. The collision tube hit! d hit! miss! Area of tube = σ = πd2 CHEM 471: Physical Chemistry In a time dt the molecule travels <s>dt. Volume of tube dV = σ<s>dt. Number of molecules per unit volume of the tube dN/dV = ρN. ⇒ dN = ρNdV= ρNσ<s>dt. Each molecule in the tube results in a collision. Number of collisions per unit time = z= dN/dt = ρNσ<s>

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