Final answer:
Lipid-anchored membrane proteins are covalently attached to a lipid group within the cell membrane, contributing to various cellular functions such as signal transduction and cell adhesion.
Step-by-step explanation:
The blank should be filled with the term lipid-anchored, leading to the phrase 'lipid-anchored membrane proteins'. These are a type of membrane protein that are covalently bonded to a lipid molecule that resides within the cell membrane. Unlike integral proteins which span across the membrane and peripheral proteins which are loosely associated with the membrane surface, lipid-anchored proteins are attached to the membrane via a lipid molecule.
Lipid-anchored proteins are important for various cellular processes, including signal transduction, cell adhesion, and maintaining the structure of the cell membrane. The lipid group that holds these proteins in place is typically linked to the protein through a post-translational modification which adds the lipid moiety to the protein, thereby anchoring it within the lipid bilayer.