A sample containing which decays by emission, disintegrates at the following rate, expressed as disintegrations per minute or counts per minute (cpm): 1000 cpm; 992 cpm; t = 10 h, 924 cpm; t = 100 h, 452 cpm; What is the half-life of this nuclide?
Enzyme regulation: absolutely necessary for optimal physiology 1) allostery : regulation at a distance 2) isozymes : enzymes with same function, differentially spatially or temporally expressed 3) covalent modification (phosphorylation) 4) proteolytic activation- enzyme is generated inactive form, activated by proteolysis control metabolism ~ totality of all biochemical activities/pathways Aspartate transcarbamylase(ATCase) aspartate + carbamoyl phosphate N-carbamoyl aspartate + PO4 committed step for pyrimidine biosynthesis -product is committed to a particular pathway Pathway regulated! Regulated by CTP and ATP Neg regulation Pos regulation Allosteric regulators As the [Asp] increases, the enzyme activity increases
