<unk> s are a class of enzymes that catalyze the decomposition of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and a free phosphate ion.  This dephosphorylation reaction releases energy, which the enzyme (in most cases) harnesses to drive other chemical reactions that would not otherwise occur.  This process is widely used in all known forms of life.
Some such enzymes are integral membrane proteins (anchored within biological membranes), and move solutes across the membrane.  (These are called transmembrane<unk> s).
ATPase
Caspase
ATP synthase
Ion transporter
Tropomyosin
Xylylcarb
NADH dehydrogenase
Ion channel