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This text provides an overview of the cell membrane, including its structure, function, and different forms of transport. It also explains the concepts of diffusion, facilitated diffusion, and osmosis, along with the effects of isotonic, hypotonic, and hypertonic solutions on cells.
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Cell Boundaries The Cell Membrane
The Cell Membrane • Thin, flexible barrier • Regulates what enters and leaves • Protectsand supports
Consists of: hydrophilic head (water liking) and a hydrophobic tail. (water avoiding) aka: Phospholipid Bilayer.
Phospholipid Bilayer: Fluid Mosaic Model • Also has • 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 • Cells get rid of wastes • Two ways: • Passive Transport – No Cell Energy (ATP) needed • Active Transport – Cell Energy (ATP) required
Passive Transport - Osmosis • 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 • Concentration of a dissolved substance (solute) is the same inside and outside the cell. • Isotonic = Dynamic equilibrium. • Cell stays same size.
Hypotonic Solution • Concentration of the solute is low outside the cell and higher inside the cell. • Water moves INTO the cell. • Cell gets BIG like the O in hypOtonic
Hypertonic Solution • Concentration of the solute is higher outside the cell and lower inside the cell. • Water Exits the cell. • Think of the “E” in hypErtonic • Cell shrinks.
Assignment • Draw and Label Figure 23, 24 and 25 on page 204-205. • Complete the Osmosis worksheet.