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 rental agreement provides for a tenancy of a short period (often 30 days) that is automatically renewed at the end of the period unless the tenant or landlord ends it by giving written notice. For these month-to-month rentals, the landlord can change the terms of the agreement with proper written notice.