Textbook Question
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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26. Prokaryotes
Prokaryotic Metabolism
2:12 minutesProblem 4
Textbook Question
Explain how feedback inhibition regulates metabolic pathways.
Verified step by step guidance1
Feedback inhibition is a regulatory mechanism where the end product of a metabolic pathway acts as an inhibitor to an enzyme involved earlier in the pathway, preventing overproduction of the product.
Identify the key enzyme in the pathway, often referred to as the 'rate-limiting enzyme,' which is typically the target of feedback inhibition.
The end product binds to the allosteric site (a site other than the active site) of the enzyme, causing a conformational change in the enzyme's structure.
This conformational change reduces the enzyme's activity, either by decreasing its ability to bind to the substrate or by reducing the catalytic efficiency of the enzyme.
As the concentration of the end product decreases, the inhibition is lifted, allowing the pathway to resume activity, thus maintaining homeostasis in the cell.
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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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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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Enzyme Regulation
Enzyme regulation refers to the various mechanisms that control enzyme activity and, consequently, the rate of metabolic reactions. This includes feedback inhibition, allosteric regulation, and covalent modification. By regulating enzyme activity, cells can respond to changes in their environment and metabolic needs, ensuring that biochemical processes are finely tuned and efficient.
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