calcium pump. the mechanism of active transport of calcium (Ca 2+) across a membrane, as of the sarcoplasmic reticulum of muscle cells, against a concentration gradient; the mechanism is driven by hydrolysis of ATP.
A rental agreement differs from a lease agreement in that it is not a long-term contract and usually occurs on a month-to-month basis. This month-to-month lease agreement expires and then renews each month upon agreement of the parties involved.
A lease is a legally binding contract, laying out the rules agreed upon between the landlord or property owner and you, the tenant. It can be from one to many pages, but in general, a lease defines exactly how long you'll be renting the apartment (six months, one year, two years and so on) and exactly how much money you'll pay in rent each month (and on what day).