Cells often use the same enzyme reaction pattern for analogous metabolic conversions. For example, the steps in the oxidation of pyruvate to acetyl-CoA and of a-ketoglutarate to succinyl-CoA, although catalyzed by different enzymes, are very similar. The first stage of fatty acid oxidation follows a reaction sequence closely resembling a sequence in the citric acid cycle. Use equations to show the analogous reaction sequences in the two pathways.

Cells often use the same enzyme reaction pattern for analogous metabolic conversions. For example, the steps in the oxidation of pyruvate to acetyl-CoA and of a-ketoglutarate to succinyl-CoA, although catalyzed by different enzymes, are very similar. The first stage of fatty acid oxidation follows a reaction sequence closely resembling a sequence in the citric acid cycle. Use equations to show the analogous reaction sequences in the two pathways.

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter23: Fatty Acid Catabolism

Section: Chapter Questions

Problem 21P: Using the ActiveModel for enoyl-CoA dehydratase, give an example of a case in which conserved...

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Cells often use the same enzyme reaction pattern for analogous metabolic conversions. For example, the steps in the oxidation of pyruvate to acetyl-CoA and of a-ketoglutarate to succinyl-CoA, although catalyzed by different enzymes, are very similar. The first stage of fatty acid oxidation follows a reaction sequence closely resembling a sequence in the citric acid cycle. Use equations to show the analogous reaction sequences in the two pathways.
In 1937, two German biochemists published a paper proposing these reactions as part of glucose oxidation: citrate → isocitrate → α-ketoglutarate →succinate → fumarate → malate → oxaloacetate. Adding succinate, fumarate, or malate to thin slices of tissue increased oxygen consumption, supporting the hypothesis that these molecules are intermediates in the process. However, they were puzzled by the observation that these intermediates were still present in the reaction mixture at the end of the experiment. They had thought that intermediates would be consumed as they were converted to the next molecule in the pathway. What explains the observation that these intermediates were still present? a) The pathway is a cycle, constantly regenerating intermediates as glucose is broken down. b) Succinate, fumarate, and malate are not reactants but catalysts, and catalysts are not consumed in the process. c) Succinate, fumarate, and malate increase metabolism and therefore oxygen consumption,…
Some bacteria use the citric acid cycle intermediate, a-ketoglutarate, plus acetyl-CoA, as the starting point for lysine biosynthesis. The first part of this biosynthetic pathway uses the same chemical strategy found in the citric acid cycle. Propose a four-step pathway for the conversion of a-ketoglutarate to 2-oxoadipate. Draw the three missing intermediates, and indicate the chemistry involved in each reaction. Include any cofactors that you think might be required for specific steps.
Fatty acids are converted to their coenzyme A esters in a reversible reaction catalyzed by acyl-CoA synthetase: R-COO +ATP +COA R-C-COA +AMP + PPi a) The reaction involves two steps the first of which forms an enzyme-bound intermediate identified as the mixed anhydride of the fatty acid and AMP: R-C-O-P-O-nibose-adenine Write two chemical equations coresponding to the two steps of the reaction catalyzed by the synthetase. b) The acyl-CoA synthetase reaction as written above is readily reversible. How might the reaction be made to favor formation of fatty acyl-CoA? Write within the box. Anything outside the box will not be graded. From the
ATP is an ALLOSTERIC INHIBITOR of the phosphofructokinase enzyme, which is a key catalyst for one of the first steps of Glycolysis. Citrate (citric acid) is a 6-carbon product of the first reaction of the Krebs Cycle (aka Citric Acid Cycle). Interestingly, Citrate enhances the inhibitory effect of ATP on phosphofructokinase. What is a likely explanation for the inhibitory effects of these molecules? Excess ATP and Citrate signal the cell that Glycolysis should be speeded up. Excess ATP and Citrate signal a positive feedback loop. Excess ATP and Citrate signal the cell that Glycolysis should be slowed. Excess ATP and Citrate compete for the active site of phosphofructokinase.
Anabolic reactions like fatty acid synthesis are inherently endergonic and require exergonic driving forces to proceed forward. Which of the following statements correctly describes the thermodynamics at play in the substrate activation step of fatty acid synthesis and the importance of this step in downstream elongation of the fatty acid chain? (A) Acetyl CoA carboxylase (ACC1) provides free energy that powers the carboxylation of acetyl CoA to form malonyl CoA.(B) The formation of malonyl CoA is powered by the exergonic carboxylation of acetyl CoA.(C) The formation of a b-ketoacyl ACP in the first step of fatty acid synthesis is driven forward because b-ketoacyl synthase hydrolyzes ATP. (D) The addition of two carbons to the growing fatty acid chain is powered by malonyl ACP decarboxylation.(E) Decarboxylation of malonyl ACP is exergonic and the free energy that is released is coupled to ATP synthesis.
Compare and contrast the pathway by which fatty acids are degraded (B-oxidation) with the pathway by which fatty acids are synthesized from acetyl-CoA. Comment on the following: (i) nature of the "activated" structures (ii) coenzymes involved (iii) stereochemistry of the intermediates (iv) sites where pathways occur
A common procedure for determining the effectiveness of compounds as precursors of glucose in mammals is to starve the animal until the liverglycogen stores are depleted and then administer the compound in question. A substrate that leads to a net increase in liver glycogen is termed glucogenic, because it must first be converted to glucose 6-phosphate. Show by means of known enzymatic reactions which of the following substances are glucogenic.
In step 2 of the fatty acid biosynthesis, the acetyl-S-synthase condenses the acetyl group (C2) with a malonyl-ACP (C3) and subsequent decarboxylation to acetoacetyl-ACP (C4). Give the molecule [A] after condensation and before decarboxylation in the reaction below. synthase (A] ACP + CO2 + HS synthase ACP HO S.
Consider the complete oxidation of one mole of simple TAG containing behenic acid residues (22:0). I. For one mole of the fatty acid residue, determine the following: a. What is the number of ATP yield obtained from the oxidation of acetyl CoA entering the TCA cycle and ETC b. What is the number of ATP yield obtained from NADH coming from the complete β-oxidation of the fatty acid residue c. What is the number of ATP yield obtained from FADH2 coming from the complete β-oxidation of the fatty acid residue d. What is the number of net ATP yield of ATP in the complete oxidation of the fatty acid residue II. What is the net ATP yield for the complete oxidation of all the fatty acid residues of the simple TAG? (Note: glycerol backbone is not included)
Part A Identify each of the following metabolic pathways. Drag the appropriate labels to their respective targets. Reset Help the conversion of fatty acids to 2-carbon units of acetyl CoA ketogenesis the conversion of an amino acid to an a-keto transamination acid the combination of 2-carbon units of acetyl COA to form fatty acids oxidative deamination the removal of an amino group as NH4+ from B oxidation glutamate to yield a-ketoglutarate lipogenesis the production of ketone bodies
Fatty acid synthesis requires the activation of acetyl CoA to malonyl CoA. However, its condensation with a fatty acyl ACP results in the addition of only its two carbons. What is the thermodynamic advantage of the activation reaction? . The condensing enzyme requires a 3-carbon compound as substrate. Cleavage of CO2 from malonyl CoA provides the energy to allow for condensation to occur. It is the activate form of the two carbon acetyl CoA necessary for condensation. It makes malonyl CoA unstable. The reaction is a reversal of the 2-oxidation which is a spontaneous process.