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 12, Problem 18P
Avidin is a protein that binds extremely tightly to biotin, so avidin is a potent inhibitor of biotin-requiring enzyme reactions. Consider glucose biosynthesis from each of the following substrates and predict which of these pathways would be inhibited by avidin.
- Lactate
- Oxaloacetate
- Malate
- Fructose-6-phosphate
- Phosphoenolpyruvate
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The following reactions are encountered in the metabolic cycles. Give the main class of enzymes that catalyzes these reactions.
glucose + pyruvate → α-ketoglutarate + alanine
lactate + NAD+ → pyruvate + NADH + H+
D-ribulose-5-phosphate → D-xylulose-5-phosphate
fructose-1-phosphate → fructose-6-phosphate
glucose + ATP → glucose-6-phosphate + ADP
starch + HOH → α-D-glucose
acetyl CoA + oxaloacetate → citric acid
pyruvate + CO2 + ATP → oxaloacetate + ADP + Pi
creatine + ATP → phosphocreatine + ADP
alanine → propanoic acid + NH3
ala-gly-val → ala + gly + val
acetylcholine ester → choline + acetic acid
triglyceride → 3 fatty acids + glycerol
deoxyribose + bases (A, G, C, T) + Pi → DNA
glyceraldehyde-3-phosphate ↔ dihydroxyacetone phosphate
Consider an alternative glycolysis pathway that starts with the phosphorylation of glucose to give glucose-6-phosphate. This (hypothetical) pathway exists in a (hypothetical) organism that does not express glucose-6-phosphate isomerase. Instead, the next step of this hypothetical pathway is a Glucose-6-Phosphate Aldolase. Draw the product or products that would be obtain by the reaction of Glucose – 6 – Phosphate with Glucose – 6 Phosphate Aldolase. Assume the reaction is completely irreversible. Explain in 1-3 sentences how you obtained your answer
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.
Chapter 12 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
Ch. 12 - Prob. 1PCh. 12 - Methanol is highly toxic, not because of its own...Ch. 12 - Prob. 3PCh. 12 - Prob. 4PCh. 12 - Prob. 5PCh. 12 - Write balanced chemical equations for each of the...Ch. 12 - Prob. 7PCh. 12 - Prob. 8PCh. 12 - Prob. 9PCh. 12 - Prob. 10P
Ch. 12 - Some anaerobic bacteria use alternative pathways...Ch. 12 - Write a pathway leading from glucose to lactose in...Ch. 12 - Prob. 13PCh. 12 - Prob. 14PCh. 12 - Prob. 15PCh. 12 - How many ATP equivalents are consumed in the...Ch. 12 - Prob. 17PCh. 12 - Avidin is a protein that binds extremely tightly...Ch. 12 - 14CO2 was bubbled through a suspension of liver...Ch. 12 - Prob. 20PCh. 12 - Prob. 21PCh. 12 - Prob. 22PCh. 12 - Prob. 23PCh. 12 - 24. Glycogen synthesis and breakdown are regulated...Ch. 12 - Prob. 25PCh. 12 - Prob. 26PCh. 12 - Prob. 27PCh. 12 - Prob. 28PCh. 12 - 29 [1-14C] Ribose-5-phosphate is incubated with a...Ch. 12 - Prob. 30PCh. 12 - Prob. 31PCh. 12 - Prob. 32PCh. 12 - Prob. 33P
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- If glucokinase has a higher Km for glucose than does hexokinase, but can only bind to D-glucose, while hexokinase can bind to several hexose sugars (like D-glucose, D-mannose, and D-fructose), then: glucokinase has both a higher affinity and a higher specificity for D-glucose than does hexokinase glucokinase has both a lower affinity and a lower specificity for D-glucose than does hexokinase glucokinase has a higher affinity but a lower specificity for D-glucose than does hexokinase glucokinase has a lower affinity but a higher specificity for D-glucose than does hexokinase all of the abovearrow_forwardThe coenzyme NAD+ is required for which glycolytic reaction shown below? Oglyceraldehyde-3-P→ 1,3-bisphosphoglycerate glucose glucose-6-P fructose-6-P→ fructose-1,6-BP 2-phosphoglycerate → phosphoenolpyruvatearrow_forwardIn 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 thisarrow_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_forwardphosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate and represents the key control point in mammalian glycolysis. The enzyme is a homotetramer that is inhibited by ATP binding, activated by AMP binding, negatively regulated by phosphorylation, and competitively inhibited by 2,5-anhydro-D-glucitol-1,6-diphosphate. (a) Would you expect a plot of the initial rate of fructose 1,6-bisphosphate formation as a function of substrate concentration to show a sigmoidal or hyperbolic curve? (b) How would each of the regulators above affect the dynamics of the T state to R state equilibrium of phosphofructokinase? Briefly explain your reasoning. (c) If it were possible to isolate phosphofructokinase monomers in an active form, how would you expect the kinetics in (a) to be affected? How would the rate of the reaction be affected by ATP, AMP, and 2,5-anhydro-D-glucitol-1,6-diphosphate? Briefly explain your answers.arrow_forwardWhy 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_forward
- An individual with chronic hypoglycemia was suspected of having a defect in one of the enzymes unique to gluconeogenesis. To identify the defective enzyme, tissue samples from a normal liver were compared to samples from the patient's liver biopsy, using a biochemical assay that measures glucose production from glycerol or malate. It was found that incubation with glycerol produced normal amounts of glucose in both the control and biopsied liver samples; however, incubation with malate did not lead to glucose production in the liver biopsy, even though it did lead to glucose production in the control liver sample. Based on these observations which of the 4 unique gluconeogenesis enzymes is most likely defective in the individual? Consider each enzyme and explain your choice, including why you ruled out enzymes that you did not choose. To answer this question review how glycerol enters gluconeogenesis (figure 9.48) and how citrate cycle metabolites are transported in and out of the…arrow_forwardVon Gierke’s disease is also known as glycogen storage disease type I. Patients with von Gierke’s disease lackglucose 6-phosphatase activity. Two prominent symptoms of this disorder are fasting hypoglycemia and lactic acidosis (elevated lactate levels in the blood), especially during strenuous exercise. Explain why these symptoms occur. What chemical reaction does this enzyme catalyze? Which pathways involve this enzyme? Lacking thisenzyme will cause impairment of which pathways?• Pls consider what pathways are affected by Von Gierke’s disease. Include in your explanation involving the Cori’s cycle.arrow_forwardVon Gierke’s disease is also known as glycogen storage disease type I. Patients with von Gierke’s disease lackglucose 6-phosphatase activity. Two prominent symptoms of this disorder are fasting hypoglycemia and lactic acidosis (elevated lactate levels in the blood), especially during strenuous exercise. Explain why these symptoms occur. What chemical reaction does this enzyme catalyze? Which pathways involve this enzyme? Lacking thisthe enzyme will cause impairment of which pathways?• Pls consider what pathways are affected by Von Gierke’s disease. Include in your explanation involving Cori’s cycle. can you please do not write by your hand? I mean computer if you can. thank youarrow_forward
- What enzyme can catalyze the committed step of the pentose phosphate pathway? Please choose one phosphopentose isomerase 6-phosphogluconate dehydrogenase lactonase phosphofructokinase glucose 6-phosphate dehydrogenasearrow_forwardLipoic Acid is the vitamin precursor for a co-enzyme called Lipoamide A patient diagnosed with lipoic acid deficiency exhibited fatigue and muscle cramps. The muscle cramps have been related to the accumulation of specific metabolic acids. On the following list, highlight the metabolic acids that are most likely to accumulate in a lipoic acid deficiency? Note: There may be more than one. Isocitrate Pyruvate Succinate α-ketoglutarate Malate Fumarate Briefly explain.arrow_forwardWhich of the following cellular concentrations would be likely to increase the rate of glycolysis? Low AMP levels High glucagon levels ✓Low fructose-2,6-bisphosphate levels High AMP levels High phosphoenolpyruvate levels Low ATP levelsarrow_forward
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