Cell Transport

• Passive transport


  NO energy, Down concentration gradient, High → Low
• Simple diffusion


  High → Low, Phospholipids: O2, CO2, alcohol, steroids, Channels: Ions – Na+ / K+, water
• Osmosis


  Special type of simple diffusion, Movement of water, Low solute → High solute
• Facilitated diffusion


  High → Low, Carriers: Glucose, Amino acids, Bind → Shape change → release
• Facilitated diffusion


  Is a passive process in which substances move with the concentration gradient
• Active transport


  Yes energy, Against concentration gradient, OR Make vesicles, Low → High
• Active transport


  Low → High, Carriers: Glucose, Amino acids, Ions, Bind → Shape change → release, Requires energy because substances being transported go against the concentration gradient
• Vesicular transport


  The movement of substances across the cell membrane in membranous bags called vesicles, Is an active process as energy is needed from the cell to form the vesicles
• Endocytosis


  Is the process of taking liquid or solids into the cell by vesicular transport, The cell membrane folds around a droplet of liquid or solid particle until it is completely enclosed
• Exocytosis


  Is when the contents of the vesicle inside the cell are passed to the outside
• Pinocytosis


  Takes in liquids into the cell
• Phagocytosis


  When the vesicles contain solid particles
• Homeostasis

  Maintenance of a constant internal environment so that cells function normally
• Intracellular fluid

  Fluid inside cells (cytoplasm)
• Extracellular fluid


  Fluid outside of cells (e.g. blood plasma and lymph)
• Intercellular fluid

  Fluid between cells (also a form of extracellular fluid)
• Cell needs - Good stuff in


  • Oxygen
  • Glucose
• Cell needs - Bad stuff out

  • Carbon dioxide
  • Water
• Substances secreted by cells

  • Hormones
  • Enzymes
• Selectively/semi-permeable cell membrane

  Some molecules/ions can pass through but not others
• Substances that move easily across the cell membrane

  • Oxygen
  • Carbon dioxide
  • Water
• Substances that cannot move across the cell membrane

  • Large molecules (glucose, amino acids)
  • Charged molecules
• Concentration gradient

  Movement of particles/molecules from an area of high concentration to an area of low concentration
• Steeper slide

  Faster movement
• Greater difference in concentration/higher concentration gradient

  Faster rate of diffusion
• Passive transport

  Does not require energy (ATP) as substances move down/with the concentration gradient
• Active transport

  Requires energy (ATP) as substances move up/against the concentration gradient
• Simple diffusion

  Molecules move from high concentration to low concentration directly through pores in the phospholipid bilayer
• Substances that undergo simple diffusion

  • Oxygen
  • Carbon dioxide
  • Alcohol
  • Steroids
  • Fat-soluble substances
• Osmosis

  Water molecules move from low solute (high water) concentration to high solute (low water) concentration
• Facilitated diffusion via channel proteins

  Molecules move from high concentration to low concentration through pores in channel proteins
• Substances that undergo facilitated diffusion via channel proteins

  • Ions (Na, K, Ca)
  • Water
• Facilitated diffusion via carrier proteins

  Molecules move from high concentration to low concentration using carrier proteins
• Substances that undergo facilitated diffusion via carrier proteins

  • Glucose
  • Amino acids
• Active carrier-mediated transport

  Requires energy (ATP) as molecules move from low concentration to high concentration using carrier proteins
• Substances that undergo active carrier-mediated transport

  • Glucose
  • Amino acids
  • Ions (Na, K, Ca)
• Advantage of active transport is that it allows transport of materials regardless of concentration gradients
• Endocytosis

  Moves substances INTO the cell using vesicles (sacs)
• Substances moved by endocytosis

  • Cholesterol
  • Iron (Fe) ions
  • Micro-organisms & cell debris (special cells only)
• Exocytosis

  Moves substances OUT OF the cell using vesicles (sacs)