the biconcave shape of erythrocytes, which maximizes rapid diffusion of oxygen, is primarily maintained by group of answer choices a relatively low concentration of integral membrane proteins allowing tighter packing of lipid molecules within the membrane. the covalent attachment of organelles to cytoskeletal components of the membrane. a network of tightly-packed anion channel proteins. a network of membrane-embedded and submembraneous proteins that form the membrane skeleton. high levels of rigid cholesterol and saturated lipids that strengthen the membrane.