Lecture Notes: Understanding Cell Membranes and Osmosis

Introduction to Osmosis Lab

• Osmosis involves water traveling through a semi-permeable membrane, like a cell membrane.
• Objective: Model osmosis in different scenarios using an egg experiment.
• Egg Experiment:
  • Soak raw eggs in vinegar for 24-48 hours to remove shells.
  • What remains is a membrane mimicking a cell membrane.

Importance of Surface Area to Volume Ratio

• Important for cell function: larger volume requires more surface area for exchange.
• Example Models:
  • Smaller models have higher surface area to volume ratio (6:1).
  • Larger models have lower ratios, demonstrating limitations on cell size.

Cell Membrane Structure

• Every living cell has a cell membrane (part of cell theory).
• Fluid Mosaic Model:
  • Describes the cell membrane as dynamic with moving components.

Components of the Cell Membrane

1. Phospholipid Bilayer

• Phospholipid Structure:
  • Amphiphilic: Polar (hydrophilic) head and non-polar (hydrophobic) tail.
  • Arranges in a bilayer with non-polar areas sandwiched in between.
• Function: Provides flexibility to the cell membrane.

2. Cholesterol

• Maintains membrane fluidity:
  • Acts as spacers at low temperatures.
  • Connects phospholipids at high temperatures.

3. Proteins

• Integral Proteins:
  • Span the membrane, involved in transport (e.g., glucose transport for ATP production).
• Peripheral Proteins:
  • Loosely attached, functions include enzyme activity and structural support.

4. Glycoproteins and Glycolipids

• Function: Cell recognition and signaling.
• Example:
  • Glycoprotein CD4 is used by immune cells and targeted by HIV.

Conclusion

• Understanding cell membrane structure aids in analyzing transport mechanisms and disease counteraction.

Note: Additional content on cell transport and videos were mentioned for further learning.