Transport across membranes

• What type of molecules can simply diffuse through the phospholipid bilayer?

  Lipid soluble molecules
• Why can't water-soluble or polar substances simply diffuse through the phospholipid bilayer?

  They cannot pass due to their properties
• What is the first type of diffusion discussed in the video?

  Simple diffusion
• What is the net movement of molecules in simple diffusion?

  From higher concentration to lower concentration
• What happens when equilibrium is reached in simple diffusion?

  Concentration is the same on both sides
• Does simple diffusion require ATP?

  No, it does not require ATP
• What type of energy do molecules possess to enable diffusion?

  Kinetic energy
• In which states of matter does simple diffusion occur?

  Liquids and gases
• What characteristics must molecules have to diffuse across the membrane?

  They must be small and lipid soluble
• How does facilitated diffusion differ from simple diffusion?

  It uses proteins embedded in the membrane
• What types of molecules typically use facilitated diffusion?

  Polar molecules and large molecules
• What is a protein channel?

  A protein embedded through the bilayer
• What do protein channels allow to pass through?

  Water-soluble ions or molecules
• How do carrier proteins function in facilitated diffusion?

  They change shape to transport molecules
• What is osmosis?

  Movement of water across a membrane
• What is the direction of water movement in osmosis?

  From higher water potential to lower water potential
• What is the unit for water potential?

  Kilopascals
• What is the water potential of pure water?

  Zero
• What happens to water potential when solutes are dissolved in water?

  It becomes negative
• What does isotonic mean in terms of water potential?

  Water potential is the same on both sides
• What is hypotonic in relation to a cell?

  More positive water potential compared to the cell
• What is hypertonic in relation to a cell?

  More negative water potential compared to the cell
• What happens to animal cells in isotonic solutions?

  No net gain of water occurs
• What happens to animal cells in hypotonic solutions?

  Water moves in, causing lysis
• How do plant cells respond in hypotonic solutions?

  They become turgid due to water intake
• What happens to cells in hypertonic solutions?

  Water leaves, causing cells to shrivel
• What is active transport?

  Movement from lower to higher concentration
• What does active transport require that other transport methods do not?

  ATP and carrier proteins
• How do carrier proteins function in active transport?

  They act as pumps to move substances
• What happens to ATP during active transport?

  It is hydrolyzed to release energy
• What is the role of inorganic phosphate in active transport?

  It helps change the shape of the protein
• What happens to the carrier protein after releasing the molecule?

  It reverts back to its original shape
• What are the main types of transport across membranes?

  • Simple diffusion
  • Facilitated diffusion
  • Osmosis
  • Active transport
• What are the key differences between isotonic, hypotonic, and hypertonic solutions?

  • Isotonic: Equal water potential
  • Hypotonic: More positive water potential
  • Hypertonic: More negative water potential
• What are the characteristics of facilitated diffusion?

  • Passive process
  • Uses protein channels or carriers
  • Moves from high to low concentration
• What are the characteristics of active transport?

  • Requires ATP
  • Moves from low to high concentration
  • Involves carrier proteins