The citric acid cycle is a critical sequence of reactions for energy production, which take place in the matrix of the mitochondria. The reaction cycle requires materials from the cytosol to be converted into acetyl CoA, which represents the starting point of a new cycle. Which of the following statements about acetyl CoA is true? (a) Acetyl CoA is recycled at the end of every cycle. (b) Oxaloacetate is attached to acetyl CoA to feed the citric acid cycle. (c) Triacylglycerol molecules are transported into the mitochondrial matrix and cleaved by lipases to produce acetyl CoA. (d) Oxaloacetate is converted directly into acetyl CoA to feed the citric acid cycle

The citric acid cycle is a critical sequence of reactions for energy production, which take place in the matrix of the mitochondria. The reaction cycle requires materials from the cytosol to be converted into acetyl CoA, which represents the starting point of a new cycle. Which of the following statements about acetyl CoA is true? (a) Acetyl CoA is recycled at the end of every cycle. (b) Oxaloacetate is attached to acetyl CoA to feed the citric acid cycle. (c) Triacylglycerol molecules are transported into the mitochondrial matrix and cleaved by lipases to produce acetyl CoA. (d) Oxaloacetate is converted directly into acetyl CoA to feed the citric acid cycle

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter19: The Tricarboxylic Acid Cycle

Section: Chapter Questions

Problem 22P: Study Figure 19.18 and decide which of the following statements is false. Pyruvate dehydrogenase is...

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Study Figure 19.18 and decide which of the following statements is false. Pyruvate dehydrogenase is inhibited byÂ· NIADH. Pyruvate dehydrogenase is inhibited by AÎ¤Î¡. Citrate synthase is inhibited by NADH. Succinyl-CoA activates citrate synthase. Acetyl-CoA activates pyruvate carboxylase.
Complete oxidation of a 16-carbon fatty acid can yield 129 molecules of ATP Study Figure 19.2 and determine how many ATP molecules would be generated if a 16-carbon fatly acid were metabolized solely by the TCA cycle, in the form of S acetyl-CoA molecules.
Ethanol as a Source of Metabolic Energy (Integrates with Chapters 19 and 20.) Acetate produced in ethanol metabolism can be transformed into acetyl-COA by the acetyl thiokinase reaction: Acetate+ATP+CoASHacetyleCoA+AMP+PPiAcetyle-CoA then can enter the citric acid cycle and undergo oxidation to 2 CO2by this route, assuming oxidative phosphorylation is part of the process? (Assume all reactions prior to acetyl-CoA entering the citric acid cycle occur outside the mitochondrion). Per carbon atom, which is a better metabolic fuel, ethanol or glucose? That is, how many ATP equivalents per carbon atom are generated by combustion of glucose versus ethanol to CO2?
The CO2 produced in one round of the citric acid cycle does not originate in the acetyl carbons that entered that round. If acetyl-CoA is labeled with 14C at its carbonyl carbon, how many rounds of the cycle are required before 14CO2 is released?
What is the final fate of the carbons in acetyl-CoA after several turns of the citric acid cycle?
If oxidation of acetyl-CoA yields 10 ATPs per mole through the citric acidcycle, how many ATPs will be derived from the complete metabolic oxidation of 1 mole of alanine in a mammal? Would the corresponding energyyield in a fish be higher or lower? Why? How much energy would bederived from the metabolic oxidation of 1 mole of isoleucine to CO2, H2O,and NH3? Of tyrosine?
Two carbon atoms are fed into the citric acid cycle as acetyl-CoA. In what form are two carbon atoms removed from the cycle?
How many cycles of "citric acid cycle" are necessary to reveal the "C" that come from acetyl-CoA that take place in the first cycle known as "CO2"?
The same reactions that were seen in the process of converting pyruvate to acetyl-S-CoA, occur in step ____ of the citric acid cycle as ____________ is converted to _________________.
One consequence of ethanol addiction is fatty liver disease, an illness in which liver cells accumulate large amounts of triacylglycerols, the esters derived from glycerol and fatty acids. Ethanol is oxidized in the cytoplasm of liver cells by alcohol dehydrogenase and aldehyde dehydrogenase to yield acetate and 2 NADH. Acetate is then transported into the mitochondrion, where it is converted to acetyl-CoA and metabolized in the citric acid cycle. When alcohol is consumed in excessive quantities, the resulting high levels of NADH cause metabolic abnormalities, one of which is high levels of fatty acid synthesis. Fatty acid synthesis, also a cytoplasmic process, uses acetyl-CoA as a substrate and NADPH as a reducing agent. Speculate about how a high level of cytoplasmic NADH provides a source of NADPH for fatty acid synthesis.
The two main goals of the citric acid cycle are: (a) citrate synthesis and gluconeogenesis (b).degradation of acetyl-CoA to produce energy and supply precursors for anabolism (c).degradation of pyruvate to produce energy and supply precursors for anabolism (d).degradation of glucose to produce energy and supply precursors for anabolism (e).degradation of pyruvate to produce energy and synthesize oxaloacetate for gluconeogenesis
Acetly CoA can quickly enter the citric acid cyle by joining with a C4 compound and forming citrate. Meanwhile, GTP (or ATP) is generated using inorganic phosphate while succinyl CoA is converted to succinate. What is the main reason both acetly CoA and succinyl CoA can perform such work? a. Acetyl CoA and succinyl CoA both contain coenzyme A, which is a high-energy compound. b. Acetyl CoA and succinyl CoA both form an unstable thioester bond with coenzyme A. c. Acetyl CoA and succinyl CoA both bind with inorganic phosphate which is used to generate ATP (or GTP). d. Acetyl CoA and succinyl CoA both transiently form a covalent bond with the enzymes that catalyze the next reaction, pyruvate dehydrogenase and succinyl-CoA synthetase, respectively. e. Acetyl CoA and succinyl CoA use the energy collected from the electron transport chain.