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• What is the main topic discussed in the video?

  Membrane transport
• What does simple diffusion involve?


  It is a passive process that does not require energy.
• What type of energy is not utilized in simple diffusion?


  No ATP is utilized.
• What direction do molecules move during simple diffusion?


  From areas of high concentration to areas of low concentration.
• What types of molecules can move through simple diffusion?


  Respiratory gases, steroid hormones, and lipid-soluble drugs.
• Why can oxygen and carbon dioxide move across the cell membrane?


  They are nonpolar and lipid-soluble.
• What is the structure of the cell membrane primarily made of?


  Phospholipids.
• What are the two components of a phospholipid?


  A polar head and nonpolar fatty acid tails.
• How do phospholipids affect the movement of charged molecules across the cell membrane?


  They repel charged molecules, preventing them from crossing.
• What does the term "like dissolves like" refer to in the context of membrane transport?


  Nonpolar substances dissolve in nonpolar environments.
• What factors affect the rate of diffusion of oxygen and carbon dioxide?


  Surface area, concentration gradient, thickness of the membrane, and weight of the molecule.
• How does surface area affect the rate of diffusion?


  A larger surface area increases the rate of diffusion.
• What happens to the rate of diffusion when the thickness of the cell membrane increases?


  The rate of diffusion decreases.
• How does the weight of a molecule affect its diffusion rate?


  Heavier molecules diffuse more slowly than lighter ones.
• What is facilitated diffusion?


  A passive process that requires transport proteins to move molecules across the membrane.
• What is osmosis?


  The movement of water from areas of high concentration to areas of low concentration.
• What are aquaporins?


  Channel proteins that facilitate the movement of water across the cell membrane.
• What are the types of channels involved in facilitated diffusion?


  • Leaky channels
  • Voltage-gated channels
  • Ligand-gated channels
  • Mechanically gated channels
• Why do charged molecules require channels to cross the cell membrane?


  Charged molecules are repelled by the phospholipid bilayer.
• What is the most important leaky channel in neurons?

  Potassium leaky channels.
• What happens to potassium ions during diffusion through leaky channels?


  Potassium ions move from areas of high concentration inside the cell to low concentration outside the cell.
• What is the role of channels in the cell membrane for charged or polar molecules?


  They allow charged or polar molecules to move across the cell membrane.
• Why are leaky channels important in neurons?


  They allow potassium to flow out of the cell, controlling the resting membrane potential.
• How does potassium move through leaky channels in neurons?


  Potassium moves from high concentration inside the cell to low concentration outside the cell.
• What triggers the opening of voltage-gated channels in neurons?


  A specific voltage threshold must be reached, such as negative 55 millivolts.
• What ions are typically involved with voltage-gated channels?


  Sodium and calcium ions.
• What is the significance of voltage-gated channels in neurons?


  They are crucial for generating action potentials.
• How do ligand-gated ion channels function?


  They open when a specific molecule, like acetylcholine, binds to them.
• What happens at the neuromuscular junction when acetylcholine binds to its receptor?


  It opens the channel, allowing sodium ions to flow into the cell.
• What is the result of sodium ions flowing into the cell at the neuromuscular junction?


  It triggers an action potential leading to muscle contraction.
• What is the role of mechanically gated channels?


  They open in response to mechanical stress or pressure.
• How does a mechanical stimulus affect pain receptors?


  It opens mechanically gated channels, allowing sodium ions to flow in and induce action potentials.
• What is carrier-mediated facilitated diffusion?


  It involves specific carriers that transport molecules like glucose across the cell membrane.
• What are GLUT transporters?


  They are carriers that facilitate the transport of glucose into cells.
• What hormone regulates GLUT4 transporters?


  Insulin.
• How does insulin affect glucose transport into cells?


  It increases the expression of GLUT4 transporters on the cell membrane.
• What is the main characteristic of facilitated diffusion?


  It is a passive process that does not require ATP.
• What is primary active transport?


  It directly uses ATP to move substances against their concentration gradient.
• What is the most important example of primary active transport?

  The sodium-potassium ATPase pump.
• How does the sodium-potassium ATPase pump function?


  It moves three sodium ions out of the cell and two potassium ions into the cell against their concentration gradients.