Chapter 15: Transport Systems in Organisms

Transport Systems in Organisms

Diffusion

• Definition: Movement of particles from high concentration to low concentration, down a concentration gradient
• Influenced by the concentration gradient; steeper gradient results in faster diffusion
• Occurs in gases, liquids, and dissolved substances, with or without a membrane
• Types of membranes:
  • Fully Permeable: All molecules can pass through
  • Impermeable: No molecules can pass through
  • Partially Permeable: Only certain molecules can pass through
• Examples in living organisms:
  • Gas exchange in lungs
  • Nutrient absorption in intestines

Osmosis

• Definition: Net movement of water molecules from a region of high water potential to low water potential through a partially permeable membrane
• Water potential gradient influences the rate of osmosis
• Water potential:
  • High: More water molecules, less solute concentration
  • Low: Fewer water molecules, higher solute concentration
• Osmosis in living systems:
  • Animal Cells (e.g., red blood cells):
    • In diluted solution: Water enters the cell, causing it to swell and possibly burst
    • In concentrated solution: Water leaves the cell, causing it to shrink and crenate
  • Plant Cells:
    • In diluted solution: Water enters the cell, making it turgid
    • In concentrated solution: Water leaves the cell, causing plasmolysis

Transport Across Cell Membrane

• Diffusion: e.g., oxygen uptake and carbon dioxide excretion during respiration
• Osmosis: e.g., water uptake by root hair cells
• Active Transport: e.g., uptake of mineral salts by root hair cells, glucose, and amino acids by epithelial cells in the small intestine

This quiz covers the concepts of diffusion, types of membranes, and transport systems in organisms, including the movement of particles and molecules across membranes.