BIO304H5 Chapter Notes - Chapter 6: Apoptosis, Exocytosis, Muscle Contraction
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2+needs to be removed from the cytoplasm quickly: cytoplasmic chelators bind free ca2+to remove it from solution, pumpsand exchangersextrude ca2+from the cytoplasm to the cell exterior or intracellular compartments (sarco/endoplasmic reticulum, mitochondria) 2. sarcoplasmic/endoplasmic reticulum calcium atpase (serca: pmca and serca are related to the na+-k+atpase, p-type (phosphorylated intermediate, however, don"t need a subunit. Pmca: 1 ca2+ion pumped out of the cell per cycle (hydrolysis of a single atp molecule, humans have 4 pmca genes, 1: brain/ubiquitous lethal if mutated, 2: brain and muscle hearing loss and balance, 3: brain and muscle, 4: broad distribution male infertility. Serca: 2 ca2+ions pumped into the sr/er per cycle (hydrolysis of a single atp molecule, humans have 3 serca genes, 1: muscle contraction, 2: muscle contraction, 3: non-muscle, but expressed in cardiomyocytes(heart) The ncx exchanger uses the na+gradient: na+ca2+exchanger, a. k. a. sodium-calcium antiporter, 1 ca2+out for 3 na+in (can thus depolarize vm!, most widely distributed sodium-calcium exchanger.
