Crossing the Membrane and Membrane Properties

Key Concepts

• Membrane Structure: Understand the fluid mosaic model, which describes the cell membrane's structure.
• Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails, forming a semipermeable membrane.

Types of Membrane Transport

• Passive Transport: No energy required; includes diffusion, osmosis, and facilitated diffusion.
  • Diffusion: Movement of molecules from high to low concentration.
  • Osmosis: Diffusion of water across a semipermeable membrane.
  • Facilitated Diffusion: Transport proteins help move substances across the membrane.
• Active Transport: Requires energy (ATP) to move substances against their concentration gradient.
  • Primary Active Transport: Direct use of ATP to transport molecules.
  • Secondary Active Transport: Indirect use of energy; relies on the gradient created by primary active transport.

Membrane Proteins

• Integral Proteins: Embedded within the lipid bilayer; include channel and carrier proteins.
• Peripheral Proteins: Loosely attached to the surface of the membrane.
• Functions: Include transport, signal transduction, and cell recognition.

Membrane Properties

• Fluidity: Affected by temperature, fatty acid chain length, and cholesterol content.
• Selectivity: Determines which molecules can enter or exit the cell.

Factors Affecting Membrane Transport

• Concentration Gradient: Difference in concentration can drive diffusion.
• Membrane Permeability: Influenced by membrane structure and molecule size.
• Temperature: Higher temperatures increase membrane fluidity and transport rates.

Additional Topics

• Endocytosis and Exocytosis: Processes by which cells intake and expel large molecules.
  • Endocytosis: Includes phagocytosis (cell eating) and pinocytosis (cell drinking).
  • Exocytosis: Vesicles fuse with the membrane to release contents outside the cell.

Study Tips

• Relate the concepts of membrane transport to real-life processes, such as nutrient absorption in the intestines.
• Use diagrams to visualize the fluid mosaic model and transport mechanisms.
• Practice using flashcards to memorize key terms and their functions.

These notes provide a comprehensive overview of the key topics related to crossing cell membranes and understanding membrane properties, useful for study and review.