A cell lacking glycoproteins on the external surface of its plasma membrane would likely be inefficient in a. transporting ions against a concentration gradient b. cell-cell recognition c. maintaining fluidity of the phospholipid bilayer d. attaching to the cytoskeleton e. establishing the diffusion barrier to charged molecules. White blood cell engulf bacteria through what process? a. exocytosis b. phagocytosis c. pinocytosis d. osmosis e. active transport During signal-transduction Ca++ and cAMP function as a. ligands. b. receptors. c. secondary messengers. d. inhibitors. e. responders