Lecture 33 notes.docx - A cell must regulate kinds and...

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A cell must regulate kinds and amounts of macromolecules they make Operon - a cluster of consecutive genes whose expression is under the control of a single regulatory site called control region Constitutive gene expression Products are constantly produced at a fixed rate No regulation or control of gene expression here Genes are effectively turned “on” all the time o code for enzymes that the cell needs in fairly large amounts for its major life processes; the enzymes used in glycolysis, or DNA replication, are examples. o The proteins are needed in the cell at about the same level under all growth conditions. Posttranslational Control Genes can be inhibited (perhaps by blocking its active site or by degrading it). Here you are controlling enzyme B’s activity so that it cannot perform the chemical reaction on its substrate. This is regulation at the level of the activity of a protein (enzyme B) after it has been synthesized, that is, posttranslationally Translational control Production can be prevented by control at the level of translation o If the message isn’t translated, the protein product insn’t made Done through RNA molecules Cells can use riboswitches o RNA molecules that help regulate transcription-some mRNAs acts as riboswitches by folding into a form that either favors or blocks translation EX: Yersinia pestis (the causative agent of plague) has this ability,
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