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General Biology: Chapter 7 Membranes

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  • What is the primary function of biological membranes?
    Biological membranes regulate the passage of substances in and out of cells and organelles, maintaining homeostasis.
  • What are the main components of a cell membrane?
    Cell membranes are mainly composed of a phospholipid bilayer, proteins, cholesterol, and carbohydrates.
  • Describe the structure of the phospholipid bilayer.
    The bilayer consists of hydrophilic phosphate heads facing outward and hydrophobic fatty acid tails facing inward.
  • What role do membrane proteins play?
    Membrane proteins assist in transport, signal transduction, cell recognition, and structural support.
  • How does cholesterol affect membrane fluidity?
    Cholesterol stabilizes membrane fluidity by preventing tight packing of phospholipids at low temperatures and restraining movement at high temperatures.
  • What is selective permeability in membranes?
    Selective permeability allows membranes to control which molecules enter or exit the cell based on size, charge, and solubility.
  • Define passive transport across membranes.
    Passive transport is the movement of molecules down their concentration gradient without energy input.
  • What is diffusion?
    Diffusion is the passive movement of molecules from an area of higher concentration to lower concentration.
  • Explain osmosis.
    Osmosis is the diffusion of water across a selectively permeable membrane toward a higher solute concentration.
  • What is facilitated diffusion?
    Facilitated diffusion uses membrane proteins to help specific molecules cross the membrane down their concentration gradient.
  • Describe active transport.
    Active transport moves molecules against their concentration gradient using energy, often from ATP.
  • What is the sodium-potassium pump?
    A membrane protein that uses ATP to pump 3 sodium ions out and 2 potassium ions into the cell, maintaining electrochemical gradients.
  • What are the two main types of membrane proteins?
    Integral proteins, which span the membrane, and peripheral proteins, which are attached to the membrane surface.
  • How do membranes contribute to cell signaling?
    Membranes contain receptor proteins that detect signals and initiate cellular responses.
  • What is endocytosis?
    Endocytosis is the process by which cells engulf external substances by folding the membrane inward.
  • Define exocytosis.
    Exocytosis is the process of vesicles fusing with the membrane to release contents outside the cell.
  • What is the fluid mosaic model?
    A model describing membranes as a fluid phospholipid bilayer with proteins embedded, moving laterally.
  • How do temperature changes affect membrane fluidity?
    Higher temperatures increase fluidity; lower temperatures decrease it, potentially causing rigidity.
  • What is the role of carbohydrates in membranes?
    Carbohydrates on membrane glycoproteins and glycolipids aid in cell recognition and adhesion.
  • Why is membrane asymmetry important?
    Asymmetry allows different functions on the inner and outer membrane surfaces, such as signaling and transport.