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Membrane Structure and Function - General Biology

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Termini in questo insieme (20)

  • Fluid Mosaic Model
    The membrane is a dynamic fluid mosaic of amphipathic phospholipids and mobile proteins that forms the cell's boundary and facilitates molecular communication.
  • Phospholipid Bilayer
    A double layer of phospholipids with hydrophilic heads facing outward and hydrophobic tails inward, forming a hydrophobic barrier in water.
  • Membrane Fluidity Regulation
    Cholesterol acts as a fluidity buffer by restraining phospholipid movement at high temperatures and preventing tight packing at low temperatures.
  • Integral vs Peripheral Proteins
    Integral proteins penetrate the hydrophobic core, often as transmembrane proteins, while peripheral proteins are loosely bound to the membrane surface.
  • Functions of Membrane Proteins
    Membrane proteins facilitate selective transport, enzymatic catalysis, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton or ECM.
  • Selective Permeability
    The hydrophobic core allows nonpolar molecules to pass easily but blocks hydrophilic substances, requiring transport proteins for their passage.
  • Facilitated Diffusion
    Transport proteins such as channel and carrier proteins provide hydrophilic pathways for molecules that cannot cross the lipid bilayer directly.
  • Aquaporins
    Specialized channel proteins that allow rapid passage of water molecules across the membrane.
  • Diffusion
    The passive movement of molecules from an area of higher concentration to lower concentration until dynamic equilibrium is reached.
  • Osmosis
    The passive diffusion of water across a selectively permeable membrane toward the side with higher solute concentration.
  • Osmoregulation
    The process by which cells control internal solute concentrations and water balance, often using contractile vacuoles to pump out excess water.
  • Turgor Pressure
    The pressure exerted by the rigid plant cell wall against the influx of water in a hypotonic environment, keeping the cell firm.
  • Active Transport
    The use of ATP to pump solutes against their concentration gradients via specific carrier proteins.
  • Sodium-Potassium Pump
    An electrogenic pump that uses ATP to exchange Na+ and K+ ions across the membrane, generating membrane potential.
  • Cotransport
    A mechanism where the downhill diffusion of one solute powers the uphill transport of another solute against its gradient.
  • Membrane Potential
    A voltage across the membrane created by electrogenic pumps, storing potential energy for cellular work.
  • Exocytosis
    The process by which cells export large molecules by fusing transport vesicles with the plasma membrane.
  • Endocytosis
    The process of capturing external materials by inward folding of the plasma membrane to form vesicles.
  • Phagocytosis vs Pinocytosis
    Phagocytosis engulfs large particles like bacteria, while pinocytosis non-selectively 'gulps' extracellular fluid and solutes.
  • Receptor-Mediated Endocytosis
    Selective uptake of specific solutes by binding to membrane receptors, forming coated vesicles for internalization.