Cell Boundaries The Cell Membrane The Cell Membrane

Cell Boundaries The Cell Membrane

The Cell Membrane Thin, flexible barrier n Regulates what enters and leaves n Protects and supports n

aka: Phospholipid Bilayer. Consists of: hydrophilic head (water liking) and a hydrophobic tail. (water avoiding)

Phospholipid Bilayer: Fluid Mosaic Model n Also has n n Proteins – doorways Carbohydrates – name tags Cholesterol – keeps membrane flexible Therefore referred to as a “fluid mosaic” of different molecules.

Cell Boundaries The Function of the Plasma Membrane

The Cell Membrane Cells want nutrients n Cells get rid of wastes n Two ways: n n n Passive Transport – No Cell Energy (ATP) needed Active Transport – Cell Energy (ATP) required

Passive Transport - Diffusion

Passive Transport – Facilitated Diffusion

Passive Transport - Osmosis n n The diffusion of water molecules through a cell membrane. Concentration gradient depends on amount of dissolved particles (like salt) inside and outside the cell.

Isotonic Solution n Concentration of a dissolved substance (solute) is the same inside and outside the cell. n Isotonic = Dynamic equilibrium. n Cell stays same size.

Isotonic Solution

Hypotonic Solution n Concentration of the solute is low outside the cell and higher inside the cell. n Water moves INTO the cell. n Cell gets BIG like the O in hyp. Otonic

Hypotonic Solution

Hypertonic Solution n n Concentration of the solute is higher outside the cell and lower inside the cell. Water n n Exits the cell. E Think of the “E” in hyp rtonic Cell shrinks.

Hypertonic Solution

Assignment n n Draw and Label Figure 23, 24 and 25 on page 204 -205. Complete the Osmosis worksheet.