The cell membrane Function : Regulates what enters and leaves the cell. Provides protection and support Selective permeability Some substances can pass across the cell membrane and others can’t

Components of the lipid bilayer Polar Head –Hydrophilic “Water Loving” Lipid Tails –Hydrophobic “Water Fearing”

Other membrane structures Protein molecules –Form channels and pumps that help to move material across the membrane

Other Membrane Structures Carbohydrate molecules –Act like ID markers for the cell –Basis for blood typing: the antigens on the blood cells (A, B, AB) are carbohydrate chains

Diffusion Definition: The movement of molecules from an area of higher concentration to an area of lower concentration, until equilibrium is reached. Concentration? Mass of Solute/Volume of solution (g/L) Diffusion of Molecules

Diffusion in Cells Molecules are able to diffuse through the cell membrane and allow the cell to function. Facilitated Diffusion – some molecules need help from protein channels to cross the cell membrane. Animation

Osmosis (A special kind of diffusion) Osmosis is the diffusion of water molecules through a selectively permeable membrane. Selectively Permeable - Osmosis

Osmosis Isotonic – concentration of solute is the same on both sides of the membrane (equilibrium) Hypertonic – the solution with a greater concentration of solute Hypotonic – the solution with the lesser concentration of solute

Passive Transport Moving down a concentration gradient is like riding a bike down a hill. It doesn’t require energy Osmosis and diffusion are examples of passive transport! ACTIVE TRANSPORT Moving up a concentration gradient is like riding up a hill. IT REQUIRES ENERGY.

Active Transport Active Transport: is the movement of materials through a cell membrane using energy. Molecules move from low concentration to high concentration. Proteins use ATP to pump ions and small molecules against concentration gradient.

Types of Active Transport 1.Endocytosis – the process of taking material into the cell by means of infoldings of the cell membrane. –Phagocytosis – extension of the cytoplasm surround and engulf the particle –Pinocytosis – similar to phagocytosis, but cells take up liquid instead of particles.

Types of Active Transport 2. Exocytosis –Large molecules move from inside the cell to outside the cell. –Contractile Vacoule – an organelle that constantly pumps H2O out of the cell. Animation

Wrap up Questions 1.Explain Diffusion 2.Explain Osmosis 3.What does selectively permeable mean? 4.What is facilitated diffusion? 5.Are phospholipids the only molecules in a cell membrane? 6.What is active transport? 7.What are tissues, organs, and organ systems? Give Examples

= cell 10% salt 20% salt 10% salt 20% salt 10% salt 20% salt Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker?

= cell 10% salt 20% salt 10% salt Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker?