MEMBRANES AND TRANSPORT MISS ESTRUCH

• What 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 through the hydrophobic layer
• What is the net movement of molecules in simple diffusion?

  From higher concentration to lower concentration
• Does simple diffusion require ATP?

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

  Kinetic energy
• In what 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
• What is the second type of diffusion mentioned in the video?

  Facilitated diffusion
• 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
• How do carrier proteins function in facilitated diffusion?

  They change shape to transport molecules
• What is osmosis?

  The movement of water across a membrane
• What direction does water move in osmosis?

  From higher water potential to lower water potential
• What type of membrane does osmosis occur through?

  A partially permeable membrane
• What is water potential?

  The pressure created by water molecules
• What is the water potential of pure water?

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

  It becomes negative
• What are the three terms used to describe solutions in relation to water potential?

  Isotonic, hypotonic, hypertonic
• What occurs to animal cells in isotonic solutions?

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

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

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

  Water leaves the cells, causing shriveling
• What is the last type of transport discussed in the video?

  Active transport
• What is the direction of movement in active transport?

  From lower concentration to higher concentration
• What does active transport require to function?

  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 mechanisms of transport across membranes?

  • Simple diffusion
  • Facilitated diffusion
  • Osmosis
  • Active transport
• What are the characteristics of isotonic, hypotonic, and hypertonic solutions?

  • Isotonic: Equal water potential on both sides
  • Hypotonic: More positive water potential outside
  • Hypertonic: More negative water potential outside
• What are the key points about diffusion?

  • Simple diffusion: High to low concentration
  • Facilitated diffusion: Uses proteins, still passive
  • Osmosis: Movement of water through a membrane
• What is the role of ATP in active transport?

  • Provides energy to move substances
  • Hydrolyzed to ADP and inorganic phosphate
  • Enables carrier proteins to change shape
• Who is the presenter of the A Level Biology video?

  1. S Trek
• What does the term "plasma membrane" refer to?

  It includes cell membranes and organelle membranes
• What model describes the structure of plasma membranes?

  Fluid mosaic model
• What does the "fluid" part of the fluid mosaic model refer to?

  Movement of molecules within the membrane
• What are the main components of the plasma membrane?

  Phospholipids, proteins, glycoproteins, glycolipids, cholesterol
• What does a partially permeable membrane allow?

  Only certain molecules to diffuse through