5. Assume the electron carriers below are all in a single chain, and that there

Question

5. Assume the electron carriers below are all in a single chain, and that there is only one entry point to the chain. What is the order in which electrons would flow spontaneously? (1) NAD+ + H' + 2e- NADH (2) FAD + 2H' +2e- FADH2 (3) Fe-S (Fe 1 eFe-S (Fe2) (4) Cyt c (Fe**) + 1 e- Cyt c (Fe'.) -0.62 +0.89 +0.22 D) 2- 1 43 E)3 4 1 2 Short Answer. Give complete and concise answers to the following questions. 6. Use the following information to answer this question. Pyruvate 2H+ 2elactate NADP" + H+ + 2 e- NADPH Eng =-0.185 V E'=-0324 V a. Write the net reaction for the reduction of pyruvate by NADPH. Calculate the Go of the reaction in (a). Please show all work. Is this reaction endergonic or b. exergonic under standard conditions? 9 pts c. Can this reaction drive ATP synthesis from ADP and Pi? Justify your answer. Remember that ATP + ADP + Pi AG-30.5 kJ/mol

Explanation / Answer

5. reduction potentials are relative to SHE(standard hydrogen electrode). a higher positive value of reduction potential means it favours reduction i.e, gain of electrons and by convention electrons flow towards the cathode where reduction occurs.

hence, looking at the values we can determine the spontaneous flow of electrons as option (E) 3->4->1->2

3 has the highest tendency to gain electrons owing to highest positive value of E, then comes 4. (in negative numbers the number with smaller digit value is greater)

6. (a) pyruvate reduction reaction is given and NADPH reduction reaction is given. just reverse the reaction for NADPH because if it reduces pyruvate it will get oxidised itself. and also, change the E sign to + when you reverse the reaction. adding both the reaction gives us the net reaction as follows-

pyruvate- + NADPH + 2H+ + 2e- -> NADP+ + 2H+ + 2e- + lactate-

(b) the Ecell = Eo(red) + Eo(oxd)

  Ecell = -0.185 + 0.324

= +0.139

delGo = -nFEcell

= -2* 96485* 0.139

delGo = -26.822 KJ The reaction is exergonic since delG <0

(c) Yes this reaction can give ATP from ADP and Pi. The delG is negative which means the reaction is spontaneous in the backward direction which is ADP + Pi -> ATP. then the sign of delG will be positive which means the reaction is favoured and spontaneous!.

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.