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Membrane Transport and Cell Signaling

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Termini in questo insieme (21)

  • What are the major components of biological membranes?
    Biological membranes are composed mainly of phospholipid bilayers with embedded proteins and cholesterol.
  • What does the Fluid Mosaic Model describe?
    The Fluid Mosaic Model describes membranes as fluid structures with a mosaic of membrane-embedded proteins that move laterally.
  • What are the two main types of membrane proteins?
    1) Integral membrane proteins span the bilayer. 2) Peripheral membrane proteins are attached to the membrane surface.
  • Name some functions of membrane proteins.
    Membrane proteins function in transport, signal transduction, cell recognition, enzymatic activity, and cytoskeleton anchoring.
  • Define concentration gradient.
    A concentration gradient is the difference in concentration of a substance between two areas.
  • What is diffusion?
    Diffusion is the movement of molecules from an area of high concentration to low concentration without energy input.
  • What does selectively permeable mean in membranes?
    Selectively permeable membranes allow some substances to cross while blocking others based on size, charge, or polarity.
  • Which molecules freely diffuse across membranes without protein facilitation?
    Small, nonpolar molecules like O2 and CO2 freely diffuse across membranes.
  • What are the two general types of molecular transport across membranes?
    1) Passive transport (no energy, down gradient). 2) Active transport (requires energy, against gradient).
  • What is the difference between passive and active transport?
    Passive transport moves substances down their concentration gradient without energy; active transport moves substances against their gradient using energy.
  • What are uniporters, symporters, and antiporters?
    Uniporters transport one molecule in one direction; symporters transport two molecules in the same direction; antiporters transport two molecules in opposite directions.
  • Define osmosis.
    Osmosis is the passive diffusion of water across a semi-permeable membrane from low to high solute concentration.
  • What is the difference between hypotonic, isotonic, and hypertonic solutions?
    Hypotonic: lower solute outside, water enters cell. Isotonic: equal solute, no net water movement. Hypertonic: higher solute outside, water leaves cell.
  • What happens to cells in hypotonic environments?
    Cells swell as water enters; plant cells become turgid, animal cells may lyse (burst).
  • What is the difference between simple diffusion and facilitated diffusion?
    Simple diffusion is direct movement of small uncharged molecules; facilitated diffusion requires transport proteins for charged or large molecules.
  • Name two types of transport proteins involved in facilitated diffusion.
    1) Channels/porins form pores for molecules. 2) Carriers/transporters undergo conformational changes to move molecules.
  • What is primary active transport?
    Primary active transport uses ATP hydrolysis to move molecules against their concentration gradient.
  • Describe the sodium-potassium pump.
    It is an active antiporter that moves 3 Na+ ions out and 2 K+ ions into the cell using ATP.
  • What is secondary active transport?
    Secondary active transport uses the concentration gradient established by primary active transport to move molecules without direct ATP use.
  • What are endocytosis and exocytosis?
    Endocytosis brings large molecules into the cell via vesicles; exocytosis expels molecules out of the cell via vesicle fusion.
  • Name the three main types of endocytosis.
    1) Phagocytosis (cell eating). 2) Pinocytosis (cell drinking). 3) Receptor-mediated endocytosis (selective uptake).