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Ch. 26 - Bacteria and Archaea
Chapter 25, Problem 4

Explain how feedback inhibition regulates metabolic pathways.

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Step 1: Understand the concept of metabolic pathways. Metabolic pathways are a series of chemical reactions that occur within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function properly.
Step 2: Learn about feedback inhibition. Feedback inhibition is a mechanism that uses the product of a metabolic pathway to control its own production by inhibiting the activity of an enzyme involved in the pathway. This is a type of negative feedback.
Step 3: Understand how feedback inhibition works. When the product of the pathway accumulates and reaches a certain concentration, it will bind to an allosteric site (a site other than the active site) on the enzyme that catalyzes the first reaction of the pathway. This changes the shape of the enzyme and inhibits its activity, slowing down or stopping the pathway.
Step 4: Recognize the importance of feedback inhibition. This mechanism allows cells to regulate how much of a certain product is made. If there is too much of a product, it will inhibit its own production, preventing wasteful overproduction. This is a key aspect of homeostasis in cells.
Step 5: Apply this knowledge to different metabolic pathways. Feedback inhibition is a common regulatory mechanism in many metabolic pathways, including the synthesis of amino acids, nucleotides, and also in the breakdown of sugars.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Feedback Inhibition

Feedback inhibition is a regulatory mechanism in metabolic pathways where the end product of a reaction inhibits an earlier step in the pathway. This process helps maintain homeostasis by preventing the overproduction of substances, ensuring that resources are used efficiently. For example, in the synthesis of isoleucine from threonine, isoleucine acts as an inhibitor of the enzyme threonine deaminase, thus regulating its own production.
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Negative Feedback

Metabolic Pathways

Metabolic pathways are series of chemical reactions occurring within a cell, where the product of one reaction serves as the substrate for the next. These pathways can be catabolic, breaking down molecules for energy, or anabolic, building complex molecules from simpler ones. Understanding these pathways is crucial for comprehending how cells convert nutrients into energy and maintain cellular functions.
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Introduction to Metabolism

Enzyme Regulation

Enzyme regulation refers to the various mechanisms that control enzyme activity and, consequently, the rate of metabolic reactions. This can occur through allosteric regulation, covalent modification, or feedback inhibition. By regulating enzyme activity, cells can respond to changes in their environment and metabolic needs, ensuring that biochemical processes are finely tuned to maintain balance and efficiency.
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Related Practice
Textbook Question

What does the chemiosmotic hypothesis claim? a. ATP is generated using phosphates taken from intermediates in the electron transport chain. b. ATP is generated using a phosphate gradient produced by glycolysis and the citric acid cycle. c. ATP is generated using a proton-motive force that is produced by the electron transport chain. d. Water is generated using electrons taken from NADH and FADH2 and transported through the electron transport chain.

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What are organisms called that use inorganic compounds as electron donors in cellular respiration? a. phototrophs b. heterotrophs c. organotrophs d. lithotrophs

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Unlike plant cell walls that contain cellulose, bacterial cell walls are composed of          .

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Textbook Question

Evaluate these statements about Koch's postulates, which are used to establish a causative link between a specific microbe and a specific disease. Select True or False for each statement. T/F The microbe must be present in individuals suffering from the disease and absent from healthy individuals. T/F The microbe must be isolated and grown in pure culture. T/F If organisms from the pure culture are injected into a healthy experimental animal, the disease symptoms should appear. T/F The microbe does not have to be isolated from the experimental animal as long as the disease is present.

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Textbook Question

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Textbook Question

Biologists often use the term 'energy source' as a synonym for 'electron donor.' Why?

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