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The Cell (aka Plasma) Membrane intro mini-movie

The Cell (aka Plasma) Membrane intro mini-movie. Functions of the Cell Membrane. Found in all cell types Is more flexible than a cell wall Controls what enters and exits the cell Forms a boundary between the cell and its environment. Selective Permeability.

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The Cell (aka Plasma) Membrane intro mini-movie

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  1. The Cell (aka Plasma) Membraneintro mini-movie

  2. Functions of the Cell Membrane • Found in all cell types • Is more flexible than a cell wall • Controls what enters and exits the cell • Forms a boundary between the cell and its environment

  3. Selective Permeability • Allows the cell to maintain homeostasis (internal balance) despite changes in its environment • Allows some, but not all, materials to cross • Small, nonpolar (uncharged) molecules pass through the membrane easily • Small, polar (charged) molecules pass through the membrane with the aid of proteins • Large molecules require vesicles to get in / out of the cell.

  4. Structure of the Cell Membrane The cell membrane consists of a double layer of phospholipids interspersed with a variety of other molecules, including proteins, cholesterol, and carbohydrates. Quick-time movie

  5. Phospholipids • A phospholipid has three major parts: • Phosphate group (which is charged) • Glycerol • Two fatty acid chains Explanation / animation

  6. Phospholipids – Heads and Tails • The phosphate and glycerol form the head, which is polar (charged) and hydrophilic (water-loving) • The two fatty acid chains form the tails, which are non-polar (not charged) and hydrophobic (water-repelling)

  7. The Phospholipid Bilayer • Cells are filled with and surrounded by water • So, phospholipids line up in a “bilayer” • Water-loving heads form the outer layer (like bread on a sandwich) • Water-repelling tails are protected inside (like the filling of a sandwich) Click for Animation

  8. The illustration above show the variety of molecules embedded within the cell membrane. • Animation

  9. Passive Transport • Particles are constantly in motion, colliding and scattering. • This motion is random. • Does not require the cell to use ATP / energy • The membrane is still semi-permeable, so only certain substances can cross (in or out) by passive transport.

  10. Passive Transport • A concentrationgradient is the difference in the concentration of a substance from one location to another • When there is a concentration gradient, the NET movement is DOWN their concentration gradient - from areas of higher concentration to areas of lower concentration ANIMATION

  11. Diffusion • Movement of molecules in a fluid or gas from an area of higher concentration to an area of lower concentration ANIMATION

  12. Equilibrium • Diffusion continues until the solution is at equilibrium (no concentration gradient). • Molecules still move, but there is no NET movement.

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