Respuesta :
Answer:
option 1,3, and 4
-Membrane proteins may be enzymes to catalyze metabolic reactions within the cell.
-Channel proteins allow a specific molecule to cross the cell membrane that is unable to cross the phospholipid bilayer unassisted.
-Receptor proteins bind to ligands, initiated cell signaling pathways.
Explanation:
I did the assignment on USATestprep and got them right.