BIOLOGY
12th Edition
ISBN: 9781260169614
Author: Raven
Publisher: RENT MCG
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Chapter 6, Problem 2S
Phosphofructokinase functions to add a phosphate group to a molecule of fructose 6-phosphate. This enzyme functions early in glycolysis, an energy-yielding biochemical pathway discussed in chapter 7. The enzyme has an active site that binds fructose and ATP. An allosteric inhibitory site also binds ATP when cellular levels of ATP are very high.
a. Predict the
b. Predict the rate of the reaction if levels of cellular ATP are very high.
c. Describe what is happening to the enzyme when levels of ATP are very high.
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Students have asked these similar questions
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.
The following Michaelis-Menten plot shows the response of phosphofructokinase-1 (PFK-1), an enzyme in the glycolytic
pathway, to the presence of ATP and AMP. Based on the data below, which of the following statements apply? Select all
that apply.
No inhibitors (low (ATP))
1 mM ATP
+ 0.1 mM AMP
1 mM ATP
1.0
2.0
(Fructose-6-phosphate) mM
Fig. : Regulation of PFK activity
AMP is an allosteric modifier that enhances the binding of the substrate fructose 6-phosphate
а.
O b. AMP is an allosteric modifier that reduces the binding of the substrate fructose 6-phosphate
ATP is an allosteric modifier that reduces the binding of the substrate fructose 6-phosphate
O c.
O d. ATP is an allosteric modifier that enhances the binding of the substrate fructose 6-phosphate
Phosphofructokinase activity
A. Explain why it is important that an energy producing pathway contains at least
one regulatory enzyme, you can use either glycolysis or TCA enzymes to
discuss this answer
B. The first step in glycolysis involves the conversion of glucose to glucose-6-
phosphate. Briefly explain how this reaction occurs as it is an endergonic
reaction.
C. Why is it important that the cell has a number of different high-energy
biomolecules?
Chapter 6 Solutions
BIOLOGY
Ch. 6.1 - Prob. 1LOCh. 6.1 - Prob. 2LOCh. 6.1 - Describe the nature of redox reactions.Ch. 6.2 - Explain the laws of thermodynamics.Ch. 6.2 - Prob. 2LOCh. 6.2 - Contrast the course of a reaction with and without...Ch. 6.3 - Describe the role of ATP in short-term energy...Ch. 6.3 - Prob. 2LOCh. 6.4 - Discuss the specificity of enzymes.Ch. 6.4 - Explain how enzymes bind to their substrates.
Ch. 6.4 - Prob. 3LOCh. 6.5 - Prob. 1LOCh. 6.5 - Prob. 2LOCh. 6.5 - Prob. 3LOCh. 6 - Prob. 1DACh. 6 - A covalent bond between two atoms represents what...Ch. 6 - During a redox reaction the molecule that gains an...Ch. 6 - Prob. 3UCh. 6 - A spontaneous reaction is one in which a. the...Ch. 6 - Prob. 5UCh. 6 - Which of the following is NOT a properly of a...Ch. 6 - Where is the energy stored in a molecule of ATP?...Ch. 6 - Prob. 1ACh. 6 - Which of the following statements is NOT true...Ch. 6 - Prob. 3ACh. 6 - Prob. 4ACh. 6 - Enzymes have similar responses to both changes in...Ch. 6 - Prob. 6ACh. 6 - Examine the graph showing the rate of reaction...Ch. 6 - Phosphofructokinase functions to add a phosphate...
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- a. Use the values in Problem 23.31 to calculate the energy change in the following reaction. fructose 1,6-bisphosphate + ADP--------> fructose 6-phosphate + ATP b. Is this reaction energetically favorable or unfavorable? c. Write this reaction using curved arrow symbolism. d. Can this reaction be used to synthesize ATP from ADP? Explain.arrow_forwardPhosphofructokinase (PFK) is the key regulatory enzyme of glycolysis. An Allosteric inhibitor of PFK is ATP. An allosteric activator is AMP (and low ATP concentrations in the cell). Draw the plot of the reaction velocity vs. fructose-6-phosphate substrate concentration for both the high ATP cell concentrations and low ATP/high AMP) concentrations.arrow_forwardCoupled reactions occur where a nonspontaneous reaction is enabled by coupling it to a spontaneous reaction. This approach is common in biological settings. Determine if ATP could be generated by this biochemical reaction. You have calculated that cell potential is +0.637V. An example of a coupled reaction is the first step of glycolysis, the phosphorylation of glucose to form glucose-6-phosphate shown below. The net ∆Gº for this reaction isarrow_forward
- . Because of the position of arsenic in the periodic table, arsenate (AsO}-) is chemically similar to inorganic phosphate and is used by phosphate-requiring enzymes as an alternative substrate. However, organic arsenates are quite unstable and spontaneously hydrolyze. Arsenate is known to inhibit ATP production in glycolysis. Identify the target enzyme, and explain the mechanism of inhibition.arrow_forwardThere 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.arrow_forwardExplain the role and functioning of chaperone proteins. Explain, why several chaperones (chaperonins) possess an ATPase activity?arrow_forward
- Match the enzyme to the reaction catalysed. Not all the enzymes have to be selected, and an enzyme may be used more than once. v Synthesizes phosphatidic acid A. Glycerol-3-phosphate dehydrogenase v Synthesizes triacylglycerol B. Glycerol kinase v Synthesizes acetoacetyl-CoA C. Acyl-CoA cholesterol acyl transferase v Synthesizes mevalonate D. Lipin v Synthesize 1,2 diacylglycerol E. Acyl transferase v Converts glycerol into glycerol-3-phosphate F. HMG-CoA reductase v Converts dihydroxyacetone phosphate into glycerol-3-phosphate G. Thiolase v Synthesize cholesterol-esterarrow_forwardGive an example of one enzyme that participates in both glycolysis and gluconeogenesis. Evaluate the structures of chemical reactants and products and the enthalpic and entropic contributions to Gibbs free energy change for the reaction. Explain how the enzyme is able to catalyze the reaction (either direction.)arrow_forwardCoupled reactions occur where a nonspontaneous reaction is enabled by coupling it to a spontaneous reaction. This approach is common in biological settings. Determine if ATP could be generated by this biochemical reaction. You have calculated that cell potential is +0.637V. An example of a coupled reaction is the first step of glycolysis, the phosphorylation of glucose to form glucose-6-phosphate shown below. kJ/mol The net AG° for this reaction is 1 2 3 н он H. H- H- H H H H 4 6. H. glucose phosphate anion glucose-6-phosphate AG = +14.0 kJ/mol 7 8 9. АТР ADP phosphate anion AG = -30.5 kJ/mol +/- LOarrow_forward
- Consider ten glucose molecules that enter a cell. How many ATP can be generated by the complete catabolism of these into CO2 and H2O? If all ten are first incorporated into glycogen, liberated from glycogen, and then fully catabolized into CO2 and H2O, does the ATP tally increase, decrease or stay the same? Consider that 1 UTP = 1 ATP. Explain. Describe the processes which produce ATP and provide a balanced equation of glucose, CO2, H2O and O2arrow_forwardDescribe the lengths of the products of the transketolase reaction when the two substrates are both five-carbon sugars.arrow_forwardBack in 1962, Gerhart and Pardee developed a model for the regulation of the activity of the ATCase enzyme by CTP and ATP, using the pathway given in Figure 1. Describe that model, using information presented here as well as what you have learned about allosteric enzymes. Be sure to include a sentence explaining the physiological significance of your model.arrow_forward
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