Prescott's Microbiology
10th Edition
ISBN: 9781259281594
Author: Joanne Willey, Linda Sherwood Adjunt Professor Lecturer, Christopher J. Woolverton Professor
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 10.7, Problem 6RIA
What is the significance of the fact that regulatory enzymes often are located at pathway branch points? What are isoenzymes, and why are they important in pathway regulation?
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What happens to the enzyme’s native conformation once it is denatured? What structural organization are destroyed by this process?
How does changes in enzymatic factors affect the native conformation of enzymes?
The products of a pathway, or the products of specific reactions in the pathway, will often inhibit upstream regulatory enzymes in that pathway. That makes sense - if the products of a pathway are abundant, then the pathway can be shut off to save energy or divert molecules into other pathways. We can use a similar rule of thumb to predict whether a pathway will be active in different biological states. For example, the liver stores glucose (in the form of glycogen), and will release glucose into the bloodstream when blood sugar levels drop. This glucose can come from the synthesis of glucose or breakdown of stored glycogen. This is important for maintaining blood sugar levels.
What would you predict is the relationship between blood sugar levels and glycogen phosphorylase enzyme activity?
A positive relationship (when blood sugar levels are high, glycogen phosphorylase activity is also high).
A negative relationship (when blood sugar levels are high, glycogen phosphorylase activity…
Many biosynthetic pathways are regulated by feedback control, where the product of a pathway turns off an enzyme that catalyzes an early step in the pathway. Usually, this control comes from an allosteric interaction. Of the types of reversible enzyme inhibition (Competitive inhibition, Noncompetitive inhibition, and Uncompetitive inhibition), what type is most likely to occur in a feedback control mechanism like this and why?
Chapter 10 Solutions
Prescott's Microbiology
Ch. 10.1 - Figure 10.2 The Relationship of G to the...Ch. 10.1 - What kinds of work are carried out in a cell?...Ch. 10.1 - What is thermodynamics? Summarize the first and...Ch. 10.1 - Define entropy and enthalpy. Do living cells...Ch. 10.1 - Prob. 4RIACh. 10.1 - Prob. 5RIACh. 10.2 - Why is ATP called a high-energy molecule? How is...Ch. 10.2 - Describe the energy cycle and ATPs role in it....Ch. 10.3 - Prob. 1MICh. 10.3 - Prob. 2MI
Ch. 10.4 - Figure 10.6 Electron Movement and Reduction...Ch. 10.4 - How is the direction of electron flow between...Ch. 10.4 - When electrons flow from the NAD+/NADH conjugate...Ch. 10.4 - Which among the following would be the best...Ch. 10.4 - In general terms, how is G related to E0? What is...Ch. 10.4 - Name and briefly describe the major electron...Ch. 10.6 - Will an enzyme with a relatively high Km have a...Ch. 10.6 - Prob. 2MICh. 10.6 - What is an apoenzyme? A holoenzyme? What are the...Ch. 10.6 - Illustrate the effect enzymes have on the...Ch. 10.6 - How does enzyme activity change with substrate...Ch. 10.6 - What special properties might an enzyme isolated...Ch. 10.6 - What are competitive and noncompetitive...Ch. 10.6 - How are enzymes and ribozymes similar? How do they...Ch. 10.7 - Figure 10.19 Allosteric Regulation. The structure...Ch. 10.7 - Figure 10.21 Feedback Inhibition. Feedback...Ch. 10.7 - Briefly describe the three ways a metabolic...Ch. 10.7 - Define the terms metabolic channeling and...Ch. 10.7 - Define allosteric enzyme and allosteric effector.Ch. 10.7 - Prob. 4RIACh. 10.7 - Prob. 5RIACh. 10.7 - What is the significance of the fact that...Ch. 10 - Examine the structures of macromolecules in...Ch. 10 - Most enzymes do not operate at their biochemical...Ch. 10 - Examine the branched pathway shown here for the...Ch. 10 - Prob. 4CHI
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- How is a “committed step” defined in the context of a metabolic pathway and why are they important? Which steps and/or enzymes are involved in the committed steps in the Krebs Cycle? What are the possible implications of these steps were deregulated?arrow_forwardWhat does it mean to say that an enzyme- catalyzed reaction is either enzyme limited or substrate -limited?arrow_forwardWhat type of enzyme regulation is the most readily (quickly) reversible?arrow_forward
- What is the reciprocal substrate relation in the synthesis of ATP and GTP?arrow_forwardIn a metabolic pathway, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate and can bind at the active site but cannot be acted upon by succinate dehydrogenase. Is Malonate a competitive or non -competitive inhibitor. What is the difference between the two types of inhibition? Can you overcome inhibition caused by Malonic acid?arrow_forwardWhat are the three most common mechanisms for enzymecatalyzed reactions that have two substrates?arrow_forward
- PTGS1 and PTGS2 are isozymes. Isozymes catalyze the same reaction, but are separate genes. What types of reactions to PTGS enzymes catalyze? Also, what pathway are these enzymes a part of?arrow_forwardIn a particular enzyme, an alanine residue is located in a cleft where the substrate binds. A mutation that changes this residue to glycine has little effect on activity; however, another mutation, which changes the alanine to a glutamate residue, leads to a complete loss of activity. Provide a brief explanation for these observations. As a follow-up on the previous question, you have another enzyme that you suspect binds its substrate in a similar site as the enzyme you are studying above. Assuming you have access to techniques whereby you could synthesize mutant proteins, outline experimental steps you would use to help you determine whether the two proteins recognize substrate by similar structural features.arrow_forwardUDP-glucuronosyltransferase enzymes bind the organic compound UDP-glucuronic acid (UDP-GA) in order to catalyse the transfer of a glucuronic acid group from UDP-GA to a drug molecule, releasing UDP from the active site as a product. UDP is then regenerated by the activity of another enzyme. What terms could be used to describe UDP-GA?arrow_forward
- When studying the mechanism of the enzymatic reaction, functional groups were found that ensure the connection of the enzyme molecule with the substrate and take a direct part in the act of catalysis. What are these areas of the enzyme formed by these groups called? What functional structures form them and why?arrow_forwardFor a lot of enzymes that work on fatty acids, the rate determining step is the release of the product from the active site. This means that the activation energy for product release is much higher than the free energy of catalysis. What enthalpic or entropic contributions would make the activation energy for product release so high and explain?arrow_forwardcreate a single illustration that will interrelate or link the two opposing pathways, the Glycogenesis and Glycogenolysis. I want you to include the enzyme in each step and include some important by-products as well. From the illustration, I want you to encircle the intermediate molecule to highlight the link between the two processes. Aside from the illustration, I want you to compare and contrast the two pathways in terms of function, number of reaction steps, and usage of UTP. You can tabulate this part to make it simpler.arrow_forward
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