Rucete ✏ Campbell Biology In a Nutshell
Unit 2 THE CELL — Concept 8.5 Regulation of Enzyme Activity Helps Control Metabolism
Cells regulate enzyme activity to maintain metabolic balance, ensuring that biochemical pathways function efficiently and respond appropriately to changing conditions.
1. Allosteric Regulation of Enzymes
Allosteric Regulation: The regulation of an enzyme's activity through the binding of regulatory molecules at specific sites (allosteric sites) other than the active site, inducing conformational changes that affect the enzyme's function.
Allosteric Activators and Inhibitors:
Activators: Bind to the allosteric site, stabilizing the enzyme's active form, thereby increasing its activity.
Inhibitors: Bind to the allosteric site, stabilizing the inactive form of the enzyme, thereby decreasing its activity.
Cooperativity: A form of allosteric regulation where the binding of a substrate to one active site in a multisubunit enzyme enhances the activity at other active sites, amplifying the enzyme's response to substrates.
2. Feedback Inhibition
Feedback Inhibition: A regulatory mechanism wherein the end product of a metabolic pathway inhibits an enzyme involved early in the pathway, preventing the overaccumulation of the product and conserving cellular resources.
Example: The synthesis of the amino acid isoleucine from threonine is regulated by feedback inhibition; as isoleucine accumulates, it inhibits the enzyme threonine deaminase, halting its own synthesis.
3. Localization of Enzymes Within the Cell
Compartmentalization: Cells organize enzymes into specific structures or organelles, facilitating the regulation and efficiency of metabolic pathways by controlling the microenvironment and proximity of enzymes to their substrates.
Example: Enzymes involved in cellular respiration are localized within mitochondria, ensuring optimal conditions for energy production.
In a Nutshell
Allosteric regulation allows cells to fine-tune enzyme activity through the binding of regulatory molecules at sites other than the active site.
Feedback inhibition prevents the overproduction of metabolic products by inhibiting pathway enzymes when end products accumulate.
Enzyme localization within specific cellular compartments enhances the efficiency and regulation of metabolic processes.