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General Biology: Cell Membranes and Energy

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  • Fluid mosaic model
    Describes the membrane structure as a fluid phospholipid bilayer with diverse protein molecules suspended within it.
  • Three general functions of the plasma membrane
    Physical barrier, cell signaling, and transport.
  • Selective permeability
    The plasma membrane's ability to allow some substances to cross more easily than others.
  • Diffusion
    The tendency of particles to spread out evenly in an available space without energy input.
  • Passive transport
    Diffusion across a membrane that requires no energy.
  • Osmosis
    The diffusion of water across a selectively permeable membrane.
  • Tonicity
    Describes the ability of a surrounding solution to cause a cell to gain or lose water.
  • Hypertonic solution effect on cells
    Cells shrink as water leaves the cell.
  • Hypotonic solution effect on cells
    Cells swell as water enters the cell.
  • Isotonic solution effect on cells
    Animal cells remain normal; plant cells become flaccid.
  • Facilitated diffusion
    Transport of polar or charged substances across membranes with the help of specific transport proteins without energy input.
  • Aquaporins
    Protein channels that facilitate rapid diffusion of water into and out of certain cells.
  • Active transport
    Energy-requiring process that moves solutes against their concentration gradient using ATP.
  • Exocytosis
    Process used by cells to export bulky molecules by packaging them in vesicles that fuse with the membrane.
  • Endocytosis
    Process used by cells to take in large molecules by engulfing them in vesicles.
  • Phagocytosis
    A type of endocytosis where the cell engulfs a particle by wrapping its membrane around it, forming a vacuole.
  • Receptor-mediated endocytosis
    Endocytosis that uses membrane receptors to take in specific solutes.
  • Kinetic energy
    Energy of motion.
  • Potential energy
    Energy stored in the location or structure of matter, including chemical energy.
  • First law of thermodynamics
    Energy can change form but cannot be created or destroyed.
  • Second law of thermodynamics
    Energy transfers increase disorder (entropy), with some energy lost as heat.
  • Exergonic reactions
    Chemical reactions that release energy.
  • Endergonic reactions
    Chemical reactions that require energy and yield products rich in potential energy.
  • ATP function
    Powers nearly all forms of cellular work by transferring phosphate groups.
  • Enzymes
    Catalysts that lower activation energy needed for reactions without being consumed.
  • Active site
    Region of an enzyme where the substrate specifically fits.
  • Competitive inhibitor
    Molecule that reduces enzyme productivity by blocking substrate binding at the active site.
  • Noncompetitive inhibitor
    Binds elsewhere on the enzyme, changing its shape so the active site no longer fits the substrate.
  • Feedback inhibition
    Regulation of metabolism where the end product inhibits an earlier step in the pathway.