• H2O • Special site (water channel) • Osmotic pressure (low to high)
Peter Agre, (Nobel Prize 2003)
6
Passive transport
• Facilitated diffusion
• Water-soluble substances can passively diffusion through the plasma membrane mediated by special membrane proteins down their electrochemical gradient.
• Voltage gated channels: • Chemically gated channels: • Mechanically gated channels:
• Character:
• High speed • Selection • Gated channels
• Example: Na+, K+, Ca2+
specialized organelles dispersed throughout a gelatin-like liquid, the cytosol.
• Cells are the bridge between molecules and humans.
2
Basic organization of cell membrane and transport
• Character:
• Specificity: • Saturation: • Competition:
• Example: glucose, amino acid