Movement in and out of cells

• Active transport is the movement of molecules across the cell membrane with the use of energy.
• Cell Membrane:

  • Semi-permeable membrane that controls the movement of substances in and out of the cell
  • Made up of a phospholipid bilayer with embedded proteins
• Diffusion:

  • Movement of particles from an area of high concentration to an area of low concentration
  • Passive process that does not require energy
• Osmosis:

  • Diffusion of water molecules across a selectively permeable membrane
  • Water moves from an area of high water potential to an area of low water potential
• Active Transport:

  • Movement of particles against a concentration gradient
  • Requires energy in the form of ATP
• Endocytosis:

  • Process by which cells take in substances by engulfing them in a vesicle
  • Types include phagocytosis (solid particles) and pinocytosis (liquid particles)
• Exocytosis:

  • Process by which cells expel substances by fusing vesicles with the cell membrane
  • Important for the release of hormones and neurotransmitters
• Factors affecting the rate of diffusion:

  • Surface area: larger surface area increases the rate of diffusion
  • Concentration gradient: steeper gradient increases the rate of diffusion
  • Temperature: higher temperature increases the rate of diffusion
• Hypotonic, hypertonic, and isotonic solutions:

  • Hypotonic: lower solute concentration outside the cell, water moves into the cell causing it to swell
  • Hypertonic: higher solute concentration outside the cell, water moves out of the cell causing it to shrink
  • Isotonic: equal solute concentration inside and outside the cell, no net movement of water