Membrane Proteins

receptor proteins

Function as binding sites for chemical signals in the extracellular fluid; binding of chemical signals to receptors triggers cellular responses

carrier proteins

move ions or molecules across the plasma membrane; binding of specific chemicals to carrier proteins causes changes in the shape of the carrier proteins; the carrier proteins then move the specific chemical across the plasma membrane

Enzymes

Catalysts for chemical reactions in living things

ATP-powered pumps

Move specific ions or molecules across the membrane; require ATP molecules to function

Marker molecules

allow cells to identify other cells or other molecules

atachment proteins

anchor cells to other cells (catherins) or to extracellular maolecules (integrins)

channel proteins

form passage ways throufh the plasma membrane, allowing specific ions or molecules to enter or exit the cell; may be leake or gated