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General Biology: Plasma Membrane and Transport Mechanisms

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이 집합의 용어 (20)

  • What is the plasma membrane and its primary function?
    The plasma membrane is present in all cells and regulates traffic across the cell, controlling what enters and leaves.
  • Define simple diffusion.
    Simple diffusion is the movement of solutes down their concentration gradient through the phospholipid bilayer without energy or assistance.
  • Define osmosis.
    Osmosis is the diffusion of the solvent (water) down its concentration gradient across a selectively permeable membrane.
  • What do hypotonic, hypertonic, and isotonic mean?
    Hypotonic: less solute; Hypertonic: more solute; Isotonic: equal solute concentration.
  • In osmosis, which moves first: solutes or water?
    Solutes always diffuse first, then water follows to balance concentrations.
  • What is the difference between simple (unfacilitated) diffusion and facilitated diffusion?
    Simple diffusion passes molecules through the bilayer directly; facilitated diffusion requires membrane proteins and is faster.
  • What factors affect the ease of molecule passage through the phospholipid bilayer?
    Smaller and more hydrophobic molecules pass more easily through the bilayer.
  • Describe the fluid mosaic model of the plasma membrane.
    The membrane is fluid due to unsaturated fatty acids and mosaic due to proteins, sugars, cholesterol, and cytoskeleton asymmetrically arranged.
  • Why is the plasma membrane called 'sugar-coated'?
    Because sugars are attached to proteins and lipids on the extracellular side, forming glycoproteins and glycolipids.
  • What are integral and peripheral proteins in the plasma membrane?
    Integral proteins span the membrane and function in transport and signaling; peripheral proteins are hydrophilic and structural.
  • What is active transport and give an example?
    Active transport moves substances against their concentration gradient using ATP, e.g., the Na+/K+ pump.
  • What is the role of the Na+/K+ pump?
    It pumps 3 Na+ ions out and 2 K+ ions into the cell, consuming 1 ATP per cycle.
  • What distinguishes passive from active transport?
    Passive transport moves substances down their concentration gradient without ATP; active transport moves substances against the gradient and requires ATP.
  • How does the concentration gradient affect diffusion?
    Molecules move from high to low concentration in passive transport, driven by the gradient.
  • What happens to a cell in a hypotonic solution?
    Water enters the cell, causing it to swell due to lower solute concentration outside.
  • What happens to a cell in a hypertonic solution?
    Water leaves the cell, causing it to shrink due to higher solute concentration outside.
  • What is the significance of membrane asymmetry?
    Different compositions on the extracellular and cytosolic sides affect membrane function and interactions.
  • What are glycoproteins and their function?
    Proteins with attached sugars involved in cell-cell recognition and signaling.
  • What is facilitated diffusion's advantage over simple diffusion?
    It allows molecules that cannot cross the bilayer to pass quickly via specific proteins.
  • How does cholesterol affect membrane fluidity?
    Cholesterol modulates fluidity by preventing tight packing of fatty acids, maintaining membrane stability.