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Simple and Facilitated Diffusion definitions

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  • Passive Transport
    Movement of molecules across a membrane without energy input, always occurring down a concentration gradient.
  • Concentration Gradient
    Difference in molecule concentration across a membrane, driving passive movement from high to low concentration.
  • Simple Diffusion
    Direct movement of small uncharged molecules through the membrane, requiring no proteins or energy.
  • Facilitated Diffusion
    Transport of charged or larger molecules across membranes with the help of proteins, but without energy use.
  • Transport Protein
    Membrane-embedded molecule that assists in moving substances across the cell membrane during facilitated diffusion.
  • Porin
    Channel-forming protein creating a tunnel through the membrane, allowing molecules to pass freely.
  • Channel
    Membrane-spanning tunnel formed by proteins, enabling ions or molecules to move across the membrane.
  • Aquaporin
    Specialized channel protein that accelerates water movement across the membrane, enhancing osmosis.
  • Transporter
    Carrier protein that changes shape to move molecules across the membrane, only open to one side at a time.
  • Carrier
    Protein facilitating molecule movement by undergoing conformational changes, not forming a continuous tunnel.
  • Osmosis
    Diffusion of water across a semi-permeable membrane, often enhanced by aquaporins.
  • Ion
    Charged particle that requires protein facilitation to cross the cell membrane during passive transport.
  • Phospholipid
    Membrane component forming a bilayer, allowing small uncharged molecules to pass during simple diffusion.
  • Conformational Change
    Structural shift in a protein enabling the transfer of molecules across the membrane in facilitated diffusion.