The plasma membrane in mammalian cells posesses unique permeability properties serving as a selective permeability barrier as well as transporters for nutrients and ions in maintaining cellular homeostasis. External ATP modulates the permeability barrier in transformed cells. The characteristics and possible mechanism for this permeability change are summarized. Application of this membrane change for cancer chemotherapy was also examined in both in vitro and in vivo. The uptake of D-glucose by mammalian cells was carried out by a facilitated diffusion through a specific transporter protein in the membrane. The control mechanism for glucose transport by growth factors based on the changes in the glucose transporter levels is summarized. Modulation of glycosylation in the transporter protein and its possible role are discussed.