MODULE 5 - MODULE 5 5.1) Modes of Regulation Regulation of...

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MODULE 5 5.1) Modes of Regulation Regulation of Transcription and Translation A given cell at a given time could be subject to diff environmental conditions requiring diff enzymes Typically, cells produce necessary enzymes only under conditions requiring those enzymes Organisms also often differentiate their cells into diff cell types under certain conditions (ex. sporulation, certain proteins produced that are only required to produce the spore) Diff levels at which enzyme activity can be turned on or off Diff strategies for regulatory mechanisms Levels of Regulation At level of transcription: no mRNA Level of translation: no enzyme Regulation of enzyme activity 5.2) Feedback Inhibition Regulation of a Pathway Pathway would only be active if level of end product is low Pathway is blocked at top of pathway even though end product has nothing to do with the enzymatic reaction taking place End product is neither substrate or product of reaction that enzyme A catalyses Allostery End product of pathway may be allosteric effector These can change enzyme’s activity If substrate able to bind to substrate binding site, enzymatic reaction proceeds
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If allosteric effector bound to allosteric site, substrate unable to bind to substrate binding site, activity of enzyme is blocked Complex Pathways Branched pathways are typical for many organisms Common pathway gives rise to end product compound Pathways are not complementary, can function concurrently or independently Regulation of pathway is specific to the pathway 5.3) Modification of Enzyme Activity Adenylation Enzyme activity can be modified by addition of AMP to a molecule Addition of ADP, phosphorylation of an enzyme and methylation of the enzyme also modify enzyme activity Glutamine synthetase is central nitrogen metabolism enzyme within the cell o Makes glutamine by adding an ammonia to glutamate o Regulation of activity can be modified according to glutamine presence o Enzyme made up of 12 identical subunits, each can be adenylated (attach AMP) o No AMP groups added means 100% enzyme activity, if 12 AMP groups added, no enzyme activity o Enzyme activity can be fine tuned according to metabolic condition of cell Transcriptonal Regulation of Activity Provision of the product of the biosynthetic pathway turns off the genes that are involved in the synthesis Lactose: presence of substrate induces presence of enzyme 5.4.1) Repression of Enzyme Activity Arginine Biosynthesis Transcription initiated by binding of RNA polymerase to promoter
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Repressor: protein that can be bound to operator
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MODULE 5 - MODULE 5 5.1) Modes of Regulation Regulation of...

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