Biological Membranes

• What surrounds all cells and organelles?

  A partially permeable membrane
• What is the main function of the cell membrane?

  Controlling movement of substances
• What molecules are found between phospholipid molecules in the membrane?

  Protein molecules
• What role do receptors in the membrane play?

  They bind to other molecules like hormones
• What is the fluid mosaic model?

  A model describing membrane structure
• What factors influence the movement of molecules through the cell membrane?

  Properties of the molecule and cell requirements
• What are the types of movement through the cell membrane?

  • Diffusion
  • Facilitated diffusion
  • Osmosis
  • Active transport
  • Exocytosis and endocytosis
• What is diffusion?

  Passive movement from high to low concentration
• Which molecules typically undergo diffusion?

  Small, non-polar lipid soluble molecules
• How do molecules move during diffusion?

  Directly through the phospholipid bilayer
• What is facilitated diffusion?

  Transport of polar and charged molecules via proteins
• What is osmosis?

  Diffusion of water through a membrane
• From where to where do water molecules move during osmosis?

  From low solute to high solute concentration
• What is another way to describe osmosis?

  Diffusion from high water potential to low
• What is active transport?

  Transport from low to high concentration using energy
• What energy form is required for active transport?

  ATP
• What do exocytosis and endocytosis transport?

  Large particles and bulk materials
• How are particles transported in endocytosis?

  Enclosed in vesicles from the membrane
• What happens during exocytosis?

  Vesicles fuse with the cell surface membrane
• What factors increase the rate of gas exchange by diffusion?

  • Increased surface area
  • Decreased diffusion distance
  • Steeper diffusion gradient
• What happens to the rate of gas exchange as surface area increases?

  It becomes more rapid
• What effect does decreased diffusion distance have on gas exchange?

  It increases the rate of exchange
• What happens when the diffusion gradient becomes steeper?

  The rate of gas exchange increases