Answer is membrane protein
Plasma membrane or cell membrane is made of lipoprotein (lipid and protein). The structure of the plasma membrane is based on the fluid mosaic model which gives basic description of the structure and behavior of membranes. The plasma membrane is a mosaic of phospholipids, cholesterol and proteins. Many proteins can move within the plasma membrane through membrane diffusion. The membrane proteins regulates the coming and going of substances into and out of the cell.