cell membrane

• the cell membrane is a selectively permeable barrier that controls the movement of substances in and out of the cell
• the cell membrane separates internal compartments of cells from the external environment.
• the cell membrane allows selective communication between intracellular and extracellular activities and controls what enters and exits the cell.
• 3 important types of protein found in the cell membrane are pores, pumps, and enzymes.
• large molecules depend on channel forming proteins to form pores to allow movement across the membrane.
• active transport is the movement of molecules or ions from a low concentration to a high concentration across the phospholipid bilayer. this requires energy. it involves specialised protein pumps, which recognise and bind to specific molecules, and then use energy from ATP to move them across the membrane.
• some enzymes which catalyse metabolic processes in the cell can be found embedded in the phospholipid membranes.