Shown below are reduction potentials for four half-reactions. Which of the coupled reactions is favorable? (Note that for Cytochrome c you must multiply the reduction potential by 2 for each coupled reaction because only one electron is involved) a) 2 Cytochrome c (Fe3+) + H2O ó 2 Cytochrome c (Fe2+) + O2 b) NADH + Succinate- ó NAD+ + Fumarate- c) Fumarate- + H2O ó Succinate- + O2 d) All of the above

Shown below are reduction potentials for four half-reactions. Which of the coupled reactions is favorable? (Note that for Cytochrome c you must multiply the reduction potential by 2 for each coupled reaction because only one electron is involved) a) 2 Cytochrome c (Fe3+) + H2O ó 2 Cytochrome c (Fe2+) + O2 b) NADH + Succinate- ó NAD+ + Fumarate- c) Fumarate- + H2O ó Succinate- + O2 d) All of the above

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter21: Photosynthesis

Section: Chapter Questions

Problem 17P

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An iron-sulfur protein in Complex 3 donates an electron to cytochrome c1. The reduction half-reactions and Eº' values are shown below. a) write the balanced equation for the reaction and calculate the standard free energy change. b) How can you account for the fact that this reaction occurs spontaneously in the cell? FeS(ox) + e- ---> FeS(red) Eº' = 0.280 V cyt c1 (Fe3+) + e- ---> cyt c1 (Fe2+) Eº' = 0.215 V
Certain bacteria can respire in anoxic environments using arsenic (V) as electron acceptor. The relevant unbalance half reactions are: H₂ AsO+H → H¸AsO +H₂O, logK = 10.84, AG = -14.5kca I m I ol-e CH₂O+H₂OH + CO2 (g), logK = 1.2, AG° = -1.63kca — ol-e 1) Balance the two half reactions 2) What is m the overall respiration reaction, standard free energy change \Delta GO 3) Is this process energetically more or less favorable than sulfate reduction? (\Delta GO for the reduction of sulfate to HS- is -5.78 kcal/mol - e-) 4) If [H2AsO4-] = [ H3ASO3] = 0.5 mM and pH = 7, estimate pe of the system
Glyceraldehyde-3-phosphate + NAD+ + Pi → 1,3-bisphosphoglycerate + NADH + H+ ∆G0’ =+6.3 kJ mol-1 ② NAD+ + H+ + 2e- → NADH ∆G0’ = +61.7 kJ mol-1 ③ Glyceraldehyde-3-phosphate + Pi → 1,3-bisphosphoglycerate + H+ + 2 e- ∆G0’ = ??? kJ mol-1 How are equations ② and ③ related to equation ①? b) Calculate the ∆G0’ for the formation of 1,3-bisphosphoglycerate from glyceraldehyde-3-phosphate and inorganic phosphate (reaction ③ above) c) Why is reaction ③ coupled with the reaction ② when reaction ② is so unfavorable, i.e., what is the chemical role of the NAD+?
The degradation of CH3 (CH₂ )10 - COOH via the beta-oxidation pathway requires: 6FAD + 6NAD+ + 5C0A-SH + 6H₂O 5FAD + 5NAD+ + 6C0A-SH+ 5H₂O 5FAD + 5NAD + 5C0A-SH + 5H₂0 6FAD + 6NAD+ + 6C0A-SH + 6H₂O
Give the product of this reaction sequence: NH3* Bg-CH3 Bg SH (cobalamin) Adenosyl-S H₂C-NH OH A Adenosyl-O intermediate D HN-CH3 Adenosyl-NH HS SH B ATP O-CH3 PPP₁ H3C-S+ Adenosyl H₂N E Adenosyl-O product OH с NH₂ S-CH3
On the right the Hill plot com- (b) pares the O2 binding properties of Hb Ya- kima with those of HbA in 0.1 M NaCl buff- Hb-Yakima ered to pH 7 with 0.01 M bis-Tris. Focus first on the line for "stripped Hb". This is the term for hemoglobin isolated from erythro- cytes with removal of all organic phosphate molecules that might bind to the protein in RBCS. You can see that 2,3-bisphospho- glycerate (BPG; labeled DPG according to old terminology) does not alter the O2 bind- ing affinity of Hb Yakima in contrast to HbA (although it was shown that BPG did bind to the deoxyHb Yakima molecule). Also, Hb Yakima is associated with markedly decreased allostery in the absence and presence of BPG, in comparison to HbA. IHP = inositol hexaphosphate, an artificial allosteric modifying ligand that binds more tightly than BPG. stripped Hb Hb-A •DPG +DPG n= 1.0 n = 2.3 n=2,5 +THP +IHP 0.5 0.5 1 5 10 50 po, ( mm Hg ) %3D On the right is a diagram copied from the lecture handout "Hemoglobin and Allo-…
Compare the delta ΔG0' values for the oxidation of succinate by NAD+ and by FAD. Use the data given in Table 18.1 to find the E0' of the NAD+-NADH and fumarate-succinate couples, and assume that E0' for the FAD – FADH2 redox couple is nearly 0.05 V. Why is FAD rather than NAD+ the electron acceptor in the reaction catalyzed by succinate dehydrogenase?
When pure reduced cytochrome c is added to carefully prepared mitochondria along with ADP, Pi, antimycin A, and oxygen, the cytochrome c becomes oxidized, and ATP is formed, with a P/O ratio approaching 1.0.(a) Indicate the probable flow of electrons in this system.(b) Why was antimycin A added?(c) What does this experiment tell you about the location of coupling sitesfor oxidative phosphorylation?(d) Write a balanced equation for the overall reaction (including cyt c oxidation and ATP synthesis).(e) Calculate ΔG°′ for the above reaction, using E′0 values from Table 14.1and a ΔG°′ value for ATP hydrolysis of -32.2 kJ/mol.
A denitrifying bacterium is strictly anaerobic. However, it possesses an electron transport chain allowing « respiration ». The final acceptor is nitrate (NO3) that is reduced in nitrite (NO₂). The electrons are introduced in the chain by the reduced nicotinamide adenine dinucleotide coenzyme (NADH + H*). 1- Write the net reaction of the electron transport chain used by the bacterium. 2- Calculate the corresponding standard Gibbs (free) energy of reaction. 3- Is the anaerobic respiration (using nitrate) more or less exergonic than the aerobic respiration (using O₂)? Justify your answer with numerical values.
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The values of the reduction potential (Eº') of the conjugated redox pairs NAD+/NADH and pyruvate / lactate are -0'32 V and -0'19 V respectively. a) Which of the two conjugated pairs has a greater tendency to lose electrons? Reason for it. b) What is the strongest oxidizing agent? Reason for it. c) If we start with 1M concentrations of each reagent and product at pH 7.0 in which sense the reaction will pass pyruvate + NADH + H+ ⇄ lactate + NAD+ d) What is the standard free energy variation (ΔGº’ at 25ºC) for the conversion of pyruvate to lactate? e) What is the equilibrium constant of this reaction?
Which cytochrome P450-catalyzed reaction is shown below? R-CH2NH2 [R-CH=NH] Oxidation of aromatic amines Oxidative deamination Oxidative O-dealkylation Oxidative N-dealkylation para-hydroxylation R-CHO + NH3