A number of systems for pumping ions across membranes are powered by atp. such atp-powered pumps are often called atpases although they don't often hydrolyze atp unless they are simultaneously transporting ions. because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using atp-powered calcium pumps. for example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (sr). if a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the sr is 10-2, then how is the atpase acting?

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Biology

Kale Flores

Today, 02:42

A number of systems for pumping ions across membranes are powered by atp. such atp-powered pumps are often called atpases although they don't often hydrolyze atp unless they are simultaneously transporting ions. because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using atp-powered calcium pumps. for example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (sr). if a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the sr is 10-2, then how is the atpase acting?

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Tommy Farrell · Answer 1

In the above question, if a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the sarcoplasmic reticulum is 10-2, then it means that the concentration of calcium ion in the cytosol is less than that in the sarcoplasmic reticulum. Since the movement of calcium ions takes place from cytosol to the sarcoplasmic membrane, the ATPase will pump the calcium ions from the cytosol to the SR against the concentration gradient.