Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 16, Problem 26P
Identify a pathway for utilization of the four carbons of acetoacetate in cholesterol biosynthesis. Carry your pathway as far as the rate-determining reaction in cholesterol biosynthesis.
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In glycolysis, the conversion of phosphoenolpyruvate (PEP) to pyruvate is considered irreversible. Yet, in gluconeogenesis, this "irreverisble" reaction is bypassed and pyruvate is eventually converted to PEP.
Explain how gluconeogenesis bypasses this irreverisble reaction. Include the enzymes required to convert pyruvate to PEP + the intermediate that is created.
Imagine a scenario where the PDH complex has picked up an "activating" mutation causing it to convert pyruvate into acetyl CoA in an unregulated manner.There is way too much acetyl CoA than is actually necessary. Explain in a sentence or two how the body would compensate for this
create a detailed flow chart or diagram that will illustrate all the important features of the glycolytic pathway. I want you to place in your flow chart or diagram the following important information like:
1. the reactants and products of each step,
2. enzymes involved in each step,
3. important by-products generated in some steps,
4. type of the reaction of each step,
5. and the outline of the two stages of the pathway.
Also, discuss briefly (4 sentences) how Galactose and Fructose enter the glycolytic pathway.
In glycolysis, the conversion of phosphoenolpyruvate (PEP) to pyruvate is considered irreversible. Yet, in gluconeogenesis, this "irreverisble" reaction is bypassed and pyruvate is eventually converted to PEP. Explain how gluconeogenesis bypasses this irreverisble reaction.
For full credit, detail:
1) The enzymes required to convert pyruvate to PEP
2) The intermediate that is created
3) The "energetic cost" of the reaction(s) (For instance, is the hydrolysis of a high-energy bond in a nucleotide triphosphate necessary?)
Chapter 16 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
Ch. 16 - Prob. 1PCh. 16 - If palmitic acid is subjected to complete...Ch. 16 - Calculate the number of ATPs generated by the...Ch. 16 - Prob. 4PCh. 16 - Prob. 5PCh. 16 - Under conditions where ketone bodies are being...Ch. 16 - Prob. 7PCh. 16 - 2-Bromopalmitoyl-CoA inhibits the oxidation of...Ch. 16 - When the identical subunits of chicken liver fatty...Ch. 16 - Prob. 10P
Ch. 16 - Prob. 11PCh. 16 - Prob. 12PCh. 16 - Prob. 13PCh. 16 - Prob. 14PCh. 16 - Prob. 15PCh. 16 - What would be the effect on fatty acid synthesis...Ch. 16 - Prob. 17PCh. 16 - Identify and briefly discuss each mechanism...Ch. 16 - Prob. 19PCh. 16 - Prob. 20PCh. 16 - Prob. 21PCh. 16 - Prob. 22PCh. 16 - Prob. 23PCh. 16 - 24. If mevalonate labeled with 14C in the carboxyl...Ch. 16 - Prob. 25PCh. 16 - Identify a pathway for utilization of the four...Ch. 16 - Prob. 27PCh. 16 - cis-Vaccenate is an 18-carbon unsaturated fatty...Ch. 16 - 29. Briefly describe how cyclic AMP controls...Ch. 16 - Prob. 30PCh. 16 - Prob. 31PCh. 16 - In addition to the pathway described in Figure...Ch. 16 - Prob. 33P
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- Strategies for regulating the central pathways in carbohydrate metabolism vary among different cells in one organism and among organisms. Slight changes in the regulation of enzymes in central metabolism can effectively re-route metabolite traffic through these pathways, just like a small mutation in PFK-1 can convert a healthy cell into a cancerous one. For instance, Gillaspera mold uses an alternative strategy for regulation the TCA and glycolysis. Gillaspera contains a unique isocitrate dehydrogenase that has an allosteric site for citrate. High citrate inhibits isocitrate dehydrogenase in this organism. Gillaspera also lacks a citrate binding site on PFK-1, so this variant of the enzyme is not affected by citrate concentrations at all. Gillaspera lacks the enzymes ethanol dehydrogenase and lactate dehydrogenase and no carbons are lost in its unique fermentation product. Would high glucose in these organisms lead to production of carbon dioxide from glucose catabolism?…arrow_forwardPhosphoglycerate mutase (PGM) catalyzes the interconversion of 3-phosphoglycerate (3PG) and 2-phosphoglycerate (2PG) in the glycolytic and gluconeogenic pathways. a) To what enzyme class does PGM belong? b) There are two distinct classes of PGM, one which is dependent on 2,3-bisphosphoglycerate (2,3-BPG), dPGM, and one which is not, iPGM. dPGM uses acid base chemistry and a phosphorylated histidine residue to interconvert 3PG and 2PG. The dPGM reaction proceeds with formation of 2,3-BPG as an intermediate. Propose a mechanism for the dPGM-catalyzed conversion of 3PG to 2PG that is consistent with this information. c) What is the purpose of 2,3-BPG (i.e., why does dPGM require it)?arrow_forwardD) Carbohydrate catabolism involves substrate-level phosphorylation. E) My answer is not here 27. The adduct acetoacetyl-acyl carrier protein is formed as an intermediate during fatty acid biosynthesis. The CO2 used to synthesize malonyl-S-CoA is lost. Would this help make the reaction more or less energetically favorable? A) Loss of CO2 increases entropy (AS) and therefore decreases the favorability of the reaction (AG). B) Loss of CO2 has no effect on entropy (AS) and therefore does not affect the favorability of the reaction (AG). C) Loss of CO2 increases entropy (AS) and therefore increases the favorability of the reaction (AG). D) Loss of CO2 decreases entropy (AS) and therefore decreases the favorability of the reaction (AG). E) Loss of CO2 decreases entropy (AS) and therefore increases the favorability of the reaction (AG).arrow_forward
- Why does it make good metabolic sense for phosphoenolpyruvate carboxykinase, rather than pyruvate carboxylase, to be the primary target for the regulation of gluconeogenesis at the level of control of enzyme synthesis? Match the words in the left column to the appropriate blanks in the sentences on the right. fructose-1,6-bisphosphate pyruvate 3-phosphoglycerate increasing reducing glycolytic pathway forward acetaldehyde lactate phosphoenolpyruvate oxaloacetate citric acid cycle back glyceraldehyde- 3-phosphate Firstly, pyruvate carboxylase converts which can participate in the gluconeogenesis pathway, and also plays an additional metabolic role in aiding the entry of intermediates into the Hence, it makes sense for phosphoenolpyruvate carboxykinase (PEPCK) to catalyze the conversion of gluconeogenesis pathway , thereby pyruvate carboxylase. to to Thirdly, PEPCK action results in the formation of amino acids and their subsequent entry into the citric acid cycle. Reset Help to push the…arrow_forwardPlease draw all of the structures of the intermediates and names of all reactants, intermediates and products, as well as the names of the enzymes. Draw the whole pathway for the catabolism of fructose into 2 lactates as it occurs in muscle tissue.arrow_forwardPlease explain the concept of a "feed-forward" mechanism and provide an example of this in the glycolytic pathway.arrow_forward
- The glucose/glucose-6-phosphate substrate cycle involves distinct reactions of glycolysis and gluconcogenesis that interconvert these two metabolites. Assume that under physiological conditions, [ATP] = [ADP] and [Pi] =1 mM. Consider the following glycolytic reaction catalyzed by hexokinase: ATP + glucose = AG' = -16.7 kJ/mol ADP + glucose-6-phosphate (a) Calculate the equilibrium constant (K) for this reaction at 298 K, and from that, calculate the maximum [glucose-6-phosphate]/[glucose] ratio that would exist under conditions where the reaction is still thermody- namically favorable. (b) The reverse of this interconversion in gluconeogenesis is catalyzed by glucose-6-phosphatase: glucose-6-phosphate + H,0 = glucose + P, AGr = -13.8 kJ/mol K= 262 for this reaction. Calculate the maximum ratio of [glucose]/ [glucose-6-phosphate] that would exist under conditions where the reaction is still thermodynamically favorable. (c) Under what cellular conditions would both directions in the…arrow_forwardFatty 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 thearrow_forwardIn fatty acid biosynthesis explain the following two parts -(a) What effect will an increase in oxaloacetate in mitochondria have on fatty acid biosynthesis?(b) How insulin and glucagon affect fatty acid oxidation and biosynthesis reactions/pathways, name them.arrow_forward
- The immediate precursor to acetyl–CoA from glycolysis is pyruvate.a) Write the pathway (not the mechanism) for the series of steps for this conversion. Includestructures for all coenzymes and reactants for each step.b) Discuss the mechanistic advantages offered by this multienzyme complex. Be specific and giveexamples.c) The last step of the reaction, catalyzed by enzyme 3, includes three coenzymes and oxidation.Write the mechanism for this enzyme.arrow_forwardOn these following choices, Malonyl CoA synthase, Malonyl CoA synthetase, Acetyl CoA carboxylase and Acetyl CoA decarboxylase, what is the correct answer in fatty acid synthesis?arrow_forward(i) Consider a preparation that contains all the enzymes and cofactors necessary for fatty acid biosynthesis from acetyl-CoA and malonyl-CoA. If [2-H] acetyl-CoA labeled with deuterium, the heavy isotope of hydrogen and excess of unlabeled malonyl-CoA are added as substrates, where will you find these labeled deuterium atoms in a molecule of palmitate synthesized? Explain. S-COA (ii) Describe the steps involved in the synthesis of palmitic acid starting from acetyl-CoA and malonyl-CoA.arrow_forward
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