When acetyl-CoA containing radioactively labeled carbon atoms is fed to cells, the CO, produced is not initially radioactive. However, molecules of citrate and oxaloacetate are radioactive. Only after some time has passed will radioactive CO2 be released. What is the best explanation for this observation?

When acetyl-CoA containing radioactively labeled carbon atoms is fed to cells, the CO, produced is not initially radioactive. However, molecules of citrate and oxaloacetate are radioactive. Only after some time has passed will radioactive CO2 be released. What is the best explanation for this observation?

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...

See similar textbooks

Similar questions

When acetyl-CoA containing radioactively labeled carbon atoms is fed to cells, the CO2 produced is not initially radioactive. However, molecules of citrate and oxaloacetate are radioactive. Only after some time has passed will radioactive CO2 be released. What is the best explanation for this observation?
The reaction catalyzed by aconitase converts citrate to isocitrate. It is strongly inhibited when it reacts with which is produced when wildlife ingests (also known as compound 1080), fluoroacetyl-CoA; fluorocitrate O fluoroacetate, fluoroacetyl-CoA Ofluorocitrate, fluoroacetyl-CoA Ofluorocitrate, fluoroacetate
In type I diabetes mellitus, excessive production of acetyl-CoA may surpass the body’s capacity to oxidize it. As a result, acetoacetate, β-hydroxybutyrate, and acetone (ketone bodies) accumulate. When generated in large amounts, blood pH falls, thereby reducing the capacity of red blood cells to carry oxygen. Explain in general terms how high concentrations of ketone bodies may result in a fatal coma.
The citric acid cycle is shown. The methyl carbon in acetyl CoA is labeled with C14C14 (shown in red). Identify which of the carbons in each intermediate will be labeled in the first round of the cycle by selecting the indicated carbon(s). Each question has multiple options, answering with only one option is incorrect. Which carbon(s) in α‑ketoglutarate will contain C14? 1 2 3 4 5 Which carbon(s) in succinyl‑CoA will contain C14? 1 2 3 4 Which carbon(s) in succinate will contain C14? 1 2 3 4 Which carbon(s) in fumarate will contain C14? 1 2 3 4 Which carbon(s) in malate will contain C14? 1 2 3 4 Which carbon(s) in oxaloacetate will contain C14? 1 2 3 4
When the acetyl-CoA produced during β-oxidation in the liver exceeds the capacity of the citric acid cycle, the excess acetyl-CoA forms ketone bodies—acetone, acetoacetate, and D-b-hydroxybutyrate. This occurs in severe, uncontrolled diabetes: because the tissues cannot use glucose, they oxidize large amounts of fatty acids instead. Although acetyl-CoA is not toxic, the mitochondrion must divert the acetyl-CoA to ketone bodies. What problem would arise if acetyl-CoA were not converted to ketone bodies? How does the diversion to ketone bodies solve the problem?
(b) Fluoroacetate, prepared commercially for rodent control, is also produced by a South African plant. After entering a cell, fluoroacetate is converted to fluoroacetyl-CoA in a reaction catalyzed by the en- zyme acetate thiokinase: F-CH2COO + CoA-SH + ATP F-CH2CO-SCOA + AMP + PP The toxic effect of fluoroacetate was studied in an experiment using intact isolated rat heart. After the heart was perfused with 0.22 mM fluoroacetate, the measured rate of glucose uptake and glycolysis decreased, and glucose 6-phosphate and fructose 6-phosphate accumulated. Examination of the citric acid cycle intermediates revealed that their concentrations were below normal, except for citrate, with a concentration 10-fold higher than normal. (b1) the other cycle intermediates to be depleted? Explain. Why does it block the citric acid cycle? Where did the block in the citric acid cycle occur? What caused citrate to accumulate and (b2) structure of the end product of fluoroacetate metabolism?…
In the first step of the TCA cycle the acetyl group of acetyl-CoA is transferred to oxaloacetate to produce citrate. Where will the carbonyl carbon of that acetyl group be after the first CO2 is expelled? Group of answer choices The first carbon of α-ketoglutarate The last carbon of α-ketoglutarate The fourth carbon of α-ketoglutarate The third carbon of α-ketoglutarate
When the acetyl-CoA produced during B-oxidation in the liver exceeds the capacity of the citric acid cycle, the excess acetyl-CoA forms ketone bodies-acetone, acetoacetate, and D-b-hydroxybutyrate. This occurs in severe, uncontrolled diabetes: because the tissues cannot use glucose, they oxidize large amounts of fatty acids instead. Although acetyl-CoA is not toxic, the mitochondrion must divert the acetyl-CoA to ketone bodies. What problem would arise if acetyl-CoA were not converted to ketone bodies? How does the diversion to ketone bodies solve the problem?
In the presence of saturating amounts of oxaloacetate, the activity of citrate synthase from pig heart tissue shows a sigmoid dependence on the concentration of acetyl‑CoA. When succinyl‑CoA is added, the curve shifts to the right and the sigmoid dependence is more pronounced.
3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase) is a very long name for the enzyme that is involved in the production of cholesterol in the human liver. The enzyme catalyzes a reaction in which electrons are exchanged between reactants to form products. This an example of which of the following chemical reactions that are involved in maintaining homeostasis? HMG-CoA reductase catalyzes a catabolic reaction because electrons are exchanged between the reactants to form products. HMG-CoA reductase catalyzes a specific type of exchange reaction called an oxidation-reduction reaction in which electrons are exchanged between reactants to form products. HMG-CoA reductase catalyzes an anabolic reaction because electrons are exchanged between the reactants to form products. HMG-CoA reductase catalyzes a specific type of oxidation-reduction reaction called an exchange reaction in which atoms are exchanged between reactants to form products. Like most enzymes, HMG-CoA reductase…
Which of the following statements is falseconcerning acetyl CoA carboxylase (ACC)? ACC is more active when protomers condense to form polymers Palmitoyl CoA serves as a feedback inhibitor The source of carbons for ACC comes from the carbon skeletons of malate that is exported from the matrix of the mitochondria in the form of malate Binding of glucagon triggers cAMP production, which leads to inhibition of ACC
The conversion of pyruvate to Acetyl-CoA involves an oxidative decarboxylation. Correct the path of the electrons through this mechanism: Pyruvate -> NAD -> lipoamide -> FAD -> TPP