Given what you know about the involvement of nicotinamidenucleotides in oxidative and reductive metabolic reactions, predictwhether the following intracellular concentration ratios should be(1) unity, (2) greater than unity, or (3) less than unity. Explain youranswers.(a) [NAD*]/[NADH](b) [NADP*]/[NADPH]Because NAD* and NADP* are essentially equivalent in their ten-dency to attract electrons, discuss how the two concentration ratiosmight be maintained inside cells at greatly differing values.

The nicotinamide nucleotides are involved in respiration as the electron donor. It is not only the…

Answered: Given what you know about the…

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter17: Metabolism: An Overview

Section: Chapter Questions

Problem 14P

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Based on your knowledge of the structure of NAD+ and an assumption that coenzyme dissociation is the rate limiting step of the alcohol dehydrogenase mechanism, hypothesize why a N249W mutation at the coenzyme binding site would increase the rate of catalysis.
Given what you know about the involvement of nicotinamide nucleotides inoxidative and reductive metabolic reactions, predict whether the followingintracellular concentration ratios should be 1, > 1, or < 1. Explain youranswers.(a) [NAD+] >[NADH](b) [NADP+] >[NADPH](c) Since NAD+ and NADP+ are essentially equivalent in their tendency to attract electrons, discuss how the two concentration ratios might bemaintained inside cells at greatly differing values.
Given the following information, calculate the physiological ΔG of the isocitrate dehydrogenase reaction at 25°C and pH 7.0: [NAD+]/[NADH] = 8, [α-ketoglutarate] = 0.1 mM, and [isocitrate] = 0.02 mM. Assume standard conditions for CO2 (ΔG°′ is given in Table). Is this reaction a likely site for metabolic control?
Why does biological Fe2+ oxidation under oxic conditions occurmainly at acidic pH?
Suppose a patient has correctly diagnosed GALT (galactose-1-phosphate uridylyltransferase) deficiency. Would this patient have lower steady state levels of NADPH in the presence of normal steady state glucose levels? Why is NADPH an important byproduct of the pentose phosphate pathway anyways?
Urea formation is energetically expensive, requiring theexpenditure of 4 mol of ATP per mole of urea formed.However, NADH is produced when fumarate is reconvertedto aspartate. How many ATP molecules are produced bythe mitochondrial oxidation of the NADH? What is the netATP requirement for urea synthesis?
The malaria parasite Plasmodium falciparum does not carry out oxidative phosphorylation and therefore does not use the citric acid cycle to generate reduced cofactors. Instead, the parasite converts amino acid–derived α ketoglutarate to succinate. Write an equation for the α-ketoglutarate → succinate conversion that follows (a) the oxidative (clockwise) path of the citric acid cycle or (b) the reductive (counterclockwise) path of the cycle.
One of the consequences of ethanol addiction is fattyliver disease, an illness in which liver cells accumulatetriacylglycerols, the esters derived from glycerol and fattyacids. Ethanol is oxidized in the cytoplasm of liver cells byalcohol dehydrogenase and aldehyde dehydrogenase to yieldacetate and 2 NADH. Acetate is then transported into themitochondrion, where it is converted to acetyl-CoA andmetabolized by the citric acid cycle. When alcohol is consumed in excessive quantities, the resulting high levels ofNADH cause metabolic abnormalities, one of which is highlevels of fatty acid synthesis. Fatty acid synthesis, also acytoplasmic process, uses acetyl-CoA as a substrate andNADPH as a reducing agent. Determine how a high level ofcytoplasmic NADH provides a source of NADPH for fattyacid synthesis.
From the complete oxidation of glucose (glucose → 6CO2), how many total NADH electron carriers are produced?
The complete combustion of palmitate and glucose yields 9781 kJ ∙ mol−1 and 2850 kJ ∙ mol−1 of free energy, respectively. Compare these values to the free energy (as ATP) obtained though catabolism of palmitate and glucose under standard conditions. Which process is more efficient?
Describe the effects of (1) oligomycin and (2) uncouplers of oxidative phosphorylation, e.g., dinitrophenol (DNP), carbonyl cyanide-p- trifluoromethoxyphenylhydrazone (FCCP), on respiration and ATP synthesis when added to a suspension of mitochondria with excess malate, ADP, and inorganic phosphate (Pi).
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?

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