Unit 2 Notes: Cell Membrane Transport

(1) Cell Membrane Definition: The semi-permeable outer-covering of all cells. Composition: 2 Phospholipid Layers (Bilayer) Protein Channels embedded Purpose / Function: Control traffic in and out of the cell Protection

(2) Cell Membrane Transport Methods: Diffusion (No energy needed) Osmosis (No energy needed) Facilitated Diffusion (No energy needed) Active Transport (Energy needed) “Transport” = Things moving in and out of the cell.

(3) Concentration Definition: The amount of matter in a given amount of space (area). High Concentration = More matter in a given amount of space. Low Concentration = Less matter in a given amount of space. “Concentration Gradient”: A difference in concentrations.

(4) Permeability Definition: The ability of matter to move across a boundary. Cell Membranes are Semi-Permeable. “Semi-Permeable”: The ability of only certain types of matter to move across a boundary.

Fully Permeable Not Permeable Semi- Permeable

(5) Equilibrium Definition: State of balance. Matter moves in and out of cells to reach equilibrium.

(6) Diffusion Definition: The movement of particles across a concentration gradient, from an area of higher concentration, to an area of lower concentration, without the use of cell energy (ATP). REMEMBER: HIGH  LOW

(7) Facilitated Diffusion Definition: The movement of larger biomolecules across protein channels in the cell membrane, without the use of energy (ATP). How is this different? Larger molecules cannot diffuse normally. Need larger membrane openings.

(8) Osmosis Definition: The movement of water particles, across a concentration gradient, from an area of higher water concentration, to an area of lower water concentration. REMEMBER: HIGH  LOW Osmotic Environments: Isotonic  Same amount of water inside + out. Hypertonic  Too much water inside the cell. Hypotonic  Not enough water inside the cell.

(9) Solute & Solvent Solute: Solid particles Sugar Salt Solvent: Liquid which dissolves solute. Water

(10) Active Transport Definition: The forced movement of molecules, across a semi-permeable membrane, AGAINST the concentration gradient, using cell energy (ATP). REMEMBER: Against the Gradient & ATP Why Would Cells Do this? Sometimes cells need a lot of a biomolecule (sugar), and need to go beyond equilibrium.

(11) The “-Cytosis” Processes Endocytosis: Bringing materials into a cell by folding them into bits of the cell membrane. Phagocytosis: A type of endocytosis where cells hunt the materials first. Pinocytosis: The endocytosis of liquid materials into the cell. Exocytosis: The releasing of materials/wastes out of the cell by wrapping them in bits of cell membrane.