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 contract made for the use of an asset. It is made between a lessor (the owner of the asset) and a lessee (the person who wants to use the asset). You will hear the most about leasing houses and cars, but you can lease anything.