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Cell Membranes and Transport - General Biology

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Termini in questo insieme (21)

  • What is the fluid-mosaic model of the plasma membrane?
    The plasma membrane is a semi-fluid, flexible bilayer of phospholipids with embedded proteins and molecules, creating a mosaic of components.
  • What does it mean that the plasma membrane is semi-permeable?
    It selectively allows certain molecules to cross in or out, regulating the cell's internal environment.
  • What are the main components of the plasma membrane?
    Phospholipids, proteins, carbohydrates, and sterols (cholesterol in animal cells).
  • Describe the structure of a phospholipid.
    A phospholipid has two unsaturated fatty acid tails (hydrophobic) and a phosphate-containing polar head (hydrophilic), making it amphipathic.
  • What role does cholesterol play in the plasma membrane?
    Cholesterol reduces membrane fluidity, acts as antifreeze in cold, and is involved in transport, signaling, and hormone synthesis.
  • What is the function of carbohydrates in the cell membrane?
    They increase cell specificity, help cells stick together to form tissues, and assist in cell recognition.
  • What is passive transport?
    Movement of substances from high to low concentration without energy input, down the concentration gradient.
  • Name the types of passive transport.
    Simple diffusion, osmosis, and facilitated diffusion.
  • What is simple diffusion?
    Movement of small non-polar molecules like O2 and CO2 directly through the phospholipid bilayer.
  • What is osmosis?
    The simple diffusion of water molecules across a semi-permeable membrane.
  • What is facilitated diffusion?
    Diffusion of molecules through a protein channel or carrier, assisting molecules that cannot cross the bilayer directly.
  • What is active transport?
    Movement of molecules against their concentration gradient using energy from ATP.
  • Name three types of energy-requiring transport.
    Active transport, exocytosis, and endocytosis.
  • What is exocytosis?
    The process of moving large molecules or groups of molecules out of the cell via vesicles, requiring ATP.
  • What is endocytosis?
    The process of taking large molecules or groups of molecules into the cell via vesicles, requiring ATP.
  • List and describe the three types of endocytosis.
    Pinocytosis (cell drinking), phagocytosis (cell eating), and receptor-mediated endocytosis (selective uptake using receptors).
  • What are transport proteins?
    Proteins that form hydrophilic channels allowing specific ions or molecules to cross the membrane, often using active transport.
  • What are receptor site proteins?
    Proteins that bind specific chemicals (ligands) to trigger a response or transport across the membrane.
  • What is the role of cell adhesion proteins?
    They help cells stick together to form tissues and regulate cell-to-cell communication.
  • What do cell recognition proteins do?
    They act as surface markers (glycoproteins) that distinguish species, individuals, and cell types, important for immune response.
  • Define tonicity and its types.
    Tonicity indicates water movement direction: hypertonic (water leaves cell), hypotonic (water enters cell), isotonic (no net water movement).