One indication of the relative importance of various ATP-producing pathways is the Vmax of certain enzymes of these pathways. The values of Vmax Oof several enzymes from the pectoral muscles (chest muscles used for flying) of pigeon and pheasant are listed below. Vmax (µmol substrate/min/g tissue) Pigeon Enzyme Pheasant Hexokinase 3.0 2.3 Glycogen phosphorylase Phosphofructokinase-1 Citrate synthase Triacylglycerol lipase Discuss the relative importance of glycogen metabolism and fat metabolism in generating ATP in the pectoral muscles of these birds. b. Compare oxygen consumption in the two birds. c. Judging from the data in the table, which bird is the long-distance flyer? Justify your answer. d. Why were these enzymes selected for comparison? Would the activities of triose phosphate isomerase and malate dehydrogenase be equally good bases for comparison? Explain. 18.0 120.0 24.0 100.0 143.0 15.0 0.07 0.01 а.

One indication of the relative importance of various ATP-producing pathways is the Vmax of certain enzymes of these pathways. The values of Vmax Oof several enzymes from the pectoral muscles (chest muscles used for flying) of pigeon and pheasant are listed below. Vmax (µmol substrate/min/g tissue) Pigeon Enzyme Pheasant Hexokinase 3.0 2.3 Glycogen phosphorylase Phosphofructokinase-1 Citrate synthase Triacylglycerol lipase Discuss the relative importance of glycogen metabolism and fat metabolism in generating ATP in the pectoral muscles of these birds. b. Compare oxygen consumption in the two birds. c. Judging from the data in the table, which bird is the long-distance flyer? Justify your answer. d. Why were these enzymes selected for comparison? Would the activities of triose phosphate isomerase and malate dehydrogenase be equally good bases for comparison? Explain. 18.0 120.0 24.0 100.0 143.0 15.0 0.07 0.01 а.

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter27: Metabolic Integration And Organ Specialization

Section: Chapter Questions

Problem 1P

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There is an enzyme that catalyzes the production of the pigment responsible for dark fur color in Siamese cats and Himalayan rabbits. This enzyme is thermolabile, meaning that it does not function at higher temperatures. Rabbits raised at 5°C are all black. If raised at 20°C, they are white with black paws, ears, and noses; they are all white when raised at 35°C. Draw an activity curve for this enzyme, and explain.
Regarding phosphofructokinase, which of the following statements is true: a. Low [ATP] stimulates the enzyme, but fructose-2,6-bisphosphate inhibits. b. High [ATP] stimulates the enzyme, but fructose-2,6-bisphosphate inhibits. c. The enzyme is more active at low [ATP] than at high, and fructose-2,6-bisphosphate activates the enzyme. d. High [ATP] stimulates the enzyme, and fructose-2,6-bisphosphate activates.
phosphofructokinase 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.
List the three different routes to catabolize glucose to Why is it necessary to start by spending one or two molecules of ATP? Why are glucose catabolism pathways ubiquitous, even in bacterial habitats where glucose is scarce? Give several Summarize the Krebs TCA cycle; list the substrates, and products.
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. ATP yield obtained from the oxidation of acetyl CoA entering the TCA cycle and ETC b. ATP yield obtained from NADH coming from the complete β-oxidation of the fatty acid residue c. ATP yield obtained from FADH2 coming from the complete β-oxidation of the fatty acid residue d. 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)
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For the following enzymes (3-6) predict how the conditions will most likely affect the enzymes activity with one of the following and provide a 1 sentence explanation: a. increase activity b. decrease activity c. not likely to alter activity 3) alpha-ketoglutarate dehydrogenase complex binding to AMP when [AMP] is high. 4) phosphohexose isomerase binding NADH when [NADH] is high 5) phosphofructose-1 binding NAD+ when [NAD+] is high 6) pyruvate dehydrogenase complex binding to ATP when [ATP] is high
draw allosteric enzyme curves comparing beta oxidation and fatty acid synthesis in the presence of high AMP and high acetyl CoA, and no regulators
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When enzyme solutions are heated, there is a progressive loss of catalytic activity over time due to denaturation of the enzyme. A solution of the enzyme hexokinase incubated at 45 °C lost 50% of its activity in 12 min, but when incubated at 45 °C in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity in 12 min. Suggest why thermal denaturation of hexokinase was retarded in the presence of one of its substrates.
Phosphofructokinase (PFK-1) is one of the most regulated enzymes in metabolism. Based on all of the principles we have learned in this class, which of the following would be most likely to be an allosteric activator of PFK-1? a Pyruvate b Acetyl CoA c Citric acid d glucose
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