transport across membranes

    Cards (33)

    • What is the fluid mosaic model of membranes?
      A model describing membrane structure
    • What does the term "fluid" refer to in the fluid mosaic model?
      Phospholipid bilayer allows movement
    • What does the term "mosaic" refer to in the fluid mosaic model?
      Proteins of different sizes and shapes embedded
    • What is the role of cholesterol in membranes?
      Reduces fluidity and stabilizes bilayer
    • What is the role of glycolipids in membranes?
      Cell signaling and recognition
    • What are the functions of extrinsic proteins in membranes?
      Binding sites / receptors, antigens (glycoprotein), binds cells together and cell signaling
    • What are the functions of intrinsic proteins in membranes?
      Electron carriers (respiration / photosynthesis), carrier proteins (facilitated diffusion) and channel proteins
    • What is one function of membranes within cells?
      Provide internal transport system
    • How do membranes regulate the passage of molecules?
      They are selectively permeable
    • What is one function of the cell-surface membrane?
      Isolates cytoplasm from extracellular environment
    • What are three factors that affect membrane permeability?
      • Temperature - denatures membrane proteins
      • pH - changes tertiary structure of membrane proteins
      • solvents - may dissolve membrane
    • How does temperature affect membrane permeability?
      High temperature denatures membrane proteins
    • How does pH affect membrane permeability?
      Changes tertiary structure of membrane proteins
    • How can solvents affect membrane permeability?
      Solvents may dissolve the membrane
    • How can colorimetry be used to investigate membrane permeability?
      1. Use plant tissue with soluble pigment.
      2. Disrupt tonoplast and cell-surface membrane.
      3. Select colorimeter filter with complementary color.
      4. Measure absorbance or % transmission value.
    • What is osmosis?
      Water diffusion across semipermeable membranes from an area of high water potential to an area of low water potential
    • What is water potential (ψ)?
      Pressure created by water molecules
    • What is the water potential of pure water at 25℃ and 100 kPa?
      0
    • How does osmosis affect plant cells?
      Protoplast swells, making cell turgid
    • How does osmosis affect animal cells?
      Causes lysis when water enters
    • What is simple diffusion?
      Passive movement of molecules (no atp) down a concentration gradient
    • What is facilitated diffusion?
      Passive transport of charged ions or polar molecules using specific proteins
    • How do channel proteins work?
      hydrophilic channels bind to specific ions and open/close channels
    • How do carrier proteins work?
      binds to complimentary molecule through conformational changes, transports molecules across
    • What are five factors that affect the rate of diffusion?
      Temperature, distance, surface area, size of molecule , concentration difference
    • What is Fick’s law?
      Surface area x concentration difference / diffusion distance
    • How are cells adapted to maximize transport rates?
      Many proteins and folded membrane to increase surface area
    • How does the graph of concentration vs. rate differ for simple vs. facilitated diffusion?
      Simple diffusion is linear; facilitated levels off
    • What is the process of active transport?
      ATP hydrolysis releases phosphate group that binds to carrier protein causing it to change shape. This carrier protein transports molecules and ions against the concentration gradient.
    • How do active transport and facilitated diffusion compare?
      Active transport requires energy from atp ; facilitated is passive
    • What is co-transport?
      Coupled movement of substances across membranes
    • How does co-transport aid in glucose absorption?
      Na+ gradient drives glucose into cells
    • What are the steps of glucose absorption via co-transport?
      1. Na+ actively transported out of epithelial cells into blood stream.
      2. Lower Na+ concentration in epithelial cells than gut lumen.
      3. Glucose/ amino acids from lumen to epithelial cells is 'coupled' to facilitated diffusion of Na+ down eletrochemical gradient
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