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Membrane Structure and Function - Lecture 4a-chapter 7-(page 1-36)(exam 2)

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Terms in this set (20)

  • What are the main components of cellular membranes?
    Lipids and proteins are the main components, with carbohydrates also playing an important role.
  • What is the structure of phospholipids in membranes?
    Phospholipids are amphipathic molecules with hydrophilic heads and hydrophobic tails, forming a bilayer.
  • Describe the fluid mosaic model of membrane structure.
    Membranes are a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids, with proteins often grouped by function.
  • How do temperature and lipid composition affect membrane fluidity?
    Membranes rich in unsaturated fatty acids are more fluid; cooling causes membranes to solidify depending on lipid types.
  • What role does cholesterol play in membrane fluidity?
    Cholesterol reduces fluidity at moderate temperatures and prevents solidification at low temperatures by disrupting packing.
  • What are the two major types of membrane proteins?
    Peripheral proteins are bound to the membrane surface; integral proteins penetrate the hydrophobic core.
  • What are transmembrane proteins?
    Integral proteins that span the entire membrane, often with hydrophobic α helices embedded in the bilayer.
  • List six functions of cell-surface membrane proteins.
    Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to cytoskeleton/ECM.
  • How do membrane carbohydrates contribute to cell recognition?
    Carbohydrates bonded to lipids (glycolipids) or proteins (glycoproteins) serve as diverse markers for cell identification.
  • What is selective permeability in membranes?
    Membranes allow some substances to cross more easily than others, regulating molecular traffic.
  • How do hydrophobic and hydrophilic molecules cross the lipid bilayer?
    Hydrophobic molecules pass rapidly through the bilayer; hydrophilic molecules cross slowly or require transport proteins.
  • What are the two types of transport proteins?
    Channel proteins provide hydrophilic tunnels; carrier proteins bind and shuttle molecules across membranes.
  • What is the function of aquaporins?
    Aquaporins are channel proteins that greatly increase water molecule passage through membranes.
  • Define diffusion in the context of membranes.
    Diffusion is the movement of particles spreading evenly, moving down their concentration gradient without energy input.
  • What is passive transport?
    The diffusion of substances across membranes without energy expenditure, driven by concentration gradients.
  • Explain osmosis.
    Osmosis is the diffusion of free water across a selectively permeable membrane from low to high solute concentration.
  • What is tonicity and how does it affect cells without cell walls?
    Tonicity is the ability of a solution to cause water movement; it affects cell volume by water gain or loss.
  • What happens to a cell in an isotonic solution?
    Water diffuses equally in both directions; cell volume remains stable.
  • What happens to a cell in a hypertonic solution?
    Water leaves the cell, causing it to shrivel and possibly die.
  • What happens to a cell in a hypotonic solution?
    Water enters the cell, causing it to swell and potentially burst (lyse).