AP Biology - Plasma Membranes Overview

Introduction

• Topic: Plasma membranes and their actions
• Importance: Key component in cell structure and function

Function of Plasma Membrane

• Separates cell from its surroundings
• Maintains a stable internal environment (homeostasis)
• Selectively permeable: Chooses what substances can enter or leave the cell

Structure of the Plasma Membrane

• Fluid Mosaic Model
  • Composed of proteins, glycoproteins, and sterols in a phospholipid bilayer
  • Fluid: Not rigid, similar to a soap bubble
  • Mosaic: Embedded proteins and molecules

Phospholipids

• Main component of plasma membrane
• Amphipathic Nature
  • Have both hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails
  • Form a bilayer: Hydrophilic heads face outwards, hydrophobic tails face inwards

Fatty Acid Tails

• Saturated vs. Unsaturated Fatty Acids
  • Unsaturated fatty acids increase membrane fluidity due to double bonds
  • Saturated fatty acids pack tightly, less fluid

Role of Cholesterol

• Increases membrane fluidity

Conclusion

• Plasma membranes play a crucial role in the functionality and structure of cells
• Understanding membrane permeability will be continued in the next session

Questions?

• Contact Mr. Poser for clarifications
• Next session: Membrane permeability