A<unk> , also called a pro-protein or pro-peptide, is an inactive protein (or peptide) that can be turned into an active form by posttranslational modification. The name of the<unk>  for a protein is often prefixed by pro. Examples include proinsulin and proopiomelanocortin.<unk> s are often used by an organism when the subsequent protein is potentially harmful, but needs to be available on short notice and/or in large quantities. Enzyme<unk> s are called zymogens or proenzymes. Examples are enzymes of the digestive tract in humans.
Some<unk> s are secreted from the cell. Many of these are synthesized with an N-terminal signal peptide that targets them for secretion. Like other proteins that contain a signal peptide, their name is prefixed by pre. They are thus called pre-pro-proteins or pre-pro-peptides. The signal peptide is cleaved off in the endoplasmic reticulum.
Protein precursor
Glycolipid
Phospholipid
Diatomic molecule
Polyphosphate
Glycerophospholipid
Glycoprotein
Transmembrane protein