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Cell Membranes & Cell Transport

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이 집합의 용어 (28)

  • Plasma membrane
    Separates the inside of the cell from the outside environment; selectively permeable, strong, and flexible.
  • Fluid mosaic model
    Membrane structure with a phospholipid bilayer and embedded proteins, cholesterol, and carbohydrates forming a mosaic.
  • Phospholipid bilayer
    Composed of hydrophilic heads facing water and hydrophobic tails forming an oily middle; allows lateral movement but no flip-flop.
  • What molecules pass through the bilayer?
    Small uncharged molecules like O2, CO2, and hydrophobic molecules such as triglycerides can pass through.
  • Cholesterol in membranes
    Adds rigidity to animal cell membranes; inserts among fatty acid tails affecting fluidity.
  • Carbohydrates on membranes
    Act as cell 'nametags' for immune recognition; found as glycoproteins and glycolipids.
  • Membrane proteins functions
    Include transport, enzymatic activity, receptors, cell ID, cell joining, and signal transduction.
  • Integral vs peripheral proteins
    Integral proteins span the membrane; peripheral proteins are often involved in signaling and attach to membrane surfaces.
  • Enzymatic activity of membrane proteins
    Proteins act as catalysts speeding reactions, e.g., ATP synthase producing ATP in mitochondria.
  • Cell-to-cell recognition
    Glycoproteins bind to immune cells; blood groups are examples of carbohydrate nametags.
  • Intercellular joining
    Includes gap junctions, desmosomes, and tight junctions that connect cells physically.
  • Signal transduction
    Membrane proteins relay external signals like hormones to the cell interior.
  • Diffusion
    Movement of molecules from higher to lower concentration; faster for gases, small molecules, and heated molecules.
  • Passive diffusion
    Molecules move down concentration gradient without energy; small neutral or hydrophobic molecules pass this way.
  • Facilitated diffusion
    Passive transport using proteins to help polar or charged molecules cross membranes.
  • Osmosis
    Passive movement of free water across membranes; water moves opposite to solute concentration.
  • Aquaporins
    Channel proteins that facilitate rapid water transport across membranes without energy use.
  • Tonicity
    Ability of a solution to cause a cell to gain or lose water; related to solute concentration differences.
  • Hypotonic solution
    Has less solute than the cell; water moves into the cell causing it to swell or burst.
  • Hypertonic solution
    Has more solute than the cell; water moves out causing the cell to shrink.
  • Isotonic solution
    Has equal solute concentration as the cell; no net water movement occurs.
  • Active transport
    Moves molecules against concentration gradient using carrier proteins and energy, usually ATP.
  • Types of active transport pumps
    Uniport (one substance), symport (two substances same direction), antiport (two substances opposite directions).
  • Na+/K+ pump
    Primary active antiport pump moving 3 Na+ out and 2 K+ in per ATP hydrolyzed; essential in animal cells.
  • Secondary active transport (cotransport)
    Uses energy from one solute moving down its gradient to move another solute against its gradient.
  • Vesicular transport
    Bulk transport of large molecules via endocytosis (phagocytosis, pinocytosis) and exocytosis.
  • Endocytosis
    Membrane engulfs particles or fluids forming vesicles to bring materials into the cell.
  • Exocytosis
    Vesicles fuse with plasma membrane to release contents outside the cell.