What is the significance of proteins for living beings?

Proteins play a fundamental role in nearly all biological processes. Because of their diversity they can assume many different configurations and they can play varied roles in cells and tissues.

Some protein functions are noteworthy: the structural function (cell membrane proteins, cytoskeleton proteins, proteins of the connective tissue), the enzymatic function (enzymes are proteins), the energy storage space function (proteins can be degraded into acetyl-CoA and "cycle" the Krebs cycle), the osmotic regulation function (albumin), the transportation function (membrane channels, respiratory pigments), the immune protection function (antibodies), the movement function (contractile proteins), the endocrine integration function (hormones) and the informative function (membrane receptors, intracellular signalers). There are also lots of proteins whose biological functions are not yet known.