Cell Membrane What is it? – Barrier that separates cell from external environment – Composed of two phospholipid layers Other molecules are embedded in the membrane

Cell Membrane – Has two major functions Forms boundary between inside and outside of the cell Controls passage of materials – Selectively permeable Some molecules can cross while others cannot

Diffusion and Osmosis How does material move across a cell membrane? Passive transport- does not require energy- two types – Diffusion – Osmosis Molecules diffuse down a concentration gradient

Diffusion and Osmosis Osmosis- diffusion of water molecules across a membrane 3 types of solutions – Isotonic – Hypertonic – Hypotonic

Diffusion and Osmosis Cell membrane channels help move molecules across Facilitated diffusion- diffusion through transport proteins

Active Transport, Endocytosis, and Exocytosis Active transport- transportation of materials against the concentration gradient – Requires energy (ATP) – Occurs through transport protein pumps – Use it to main homeostasis

Active Transport, Endocytosis, and Exocytosis Endocytosis- carry larger molecules into the cell using vesicles – Phagocytosis- moves particles or whole cells in – Pinocytosis- moves fluids in Exocytosis- taking larger molecules out of the cell