Lecture Notes: Osmosis and Cell Membranes

Introduction to Osmosis

• Osmosis Definition: Movement of water through a semi-permeable membrane.
• Experiment Concept: Using eggs to model osmosis.
  • Soak raw eggs in vinegar for 24-48 hours to remove the shell, leaving the membrane.
  • This membrane acts as a cell membrane for osmosis experiments.

Cell Membrane and Surface Area

• Membrane as a Semi-Permeable Barrier
  • Controls intake and outflow of substances.
  • Provides a model for understanding cell transport.
• Importance of Surface Area
  • Surface area impacts food intake and waste removal.
  • Smaller cells have larger surface area to volume ratios, essential for efficiency.

Fluid Mosaic Model

• Definition: Describes the cell membrane structure.
  • Mosaic: Many small parts making up a larger structure.
  • Fluid: Components in constant motion.

Phospholipid Bilayer

• Phospholipids: Lipids with polar heads and nonpolar tails.
  • Hydrophilic Heads: Attract water.
  • Hydrophobic Tails: Repel water.
• Arrangement: Forms a bilayer with hydrophobic tails inward.
• Movement: Lipids are dynamic, providing flexibility.

Role of Cholesterol

• Function: Maintains membrane stability.
  • Acts as spacers in cold temperatures.
  • Connects phospholipids in warm temperatures.

Proteins in Cell Membrane

• Peripheral Proteins
  • Located on membrane surface.
  • Functions: Enzymatic activity, structural support.
• Integral Proteins
  • Span the membrane.
  • Functions: Transport of substances like glucose.

Glycoproteins and Glycolipids

• Glycoproteins: Proteins with carbohydrates attached.
  • Role in cell recognition and signaling.
• Glycolipids: Lipids with carbohydrates attached.
  • Involved in self and non-self recognition.

Practical Application

• CD4 Glycoprotein: Important for immune interactions, targeted by HIV.
• Understanding Membranes: Essential for combating viral/bacterial diseases.

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Remember to stay curious and continue exploring cell biology concepts!