Fat4

• Active transport


  Transport of substances through cell membrane against concentration gradient (uphill), or electric gradients, or both (physico-chemical or electrochemical gradient)

  
• Active transport


  • Requires energy (ATP); either direct or indirect
  • Requires a carrier protein (with ATPase activity)
• Types of active transport

  • Primary active transport
  • Secondary active transport
• Primary active transport


  Energy is derived directly from breakdown of ATP (or other high energy phosphate compounds)
• Primary active transport


  • Sodium-Potassium pump (Na+-K+ pump)
  • Ca++ ATPase pump
  • H+ ATPase pump
• Sodium-Potassium pump (Na+-K+ pump)


  • Present in all cell membranes
  • Transports 3 Na+ out (efflux) and 2K+ in (influx)
  • Electrogenic pump, creates electrical potential across cell membrane

  
• Secondary active transport


  Transport of one or more solutes against an electrochemical gradient, coupled to the transport of another solute down an electrochemical gradient
• Types of secondary active transport

  • Co-transport
  • Counter-transport
• Co-transport


  Transport of two substances in the same direction, all solutes move into the cell
• Co-transport


  • Na+ – glucose
  • Na+ – amino acid

  
• Counter-transport


  Transport of two substances in opposite direction, Na+ moves into the cell causing other substance to move out

  
• Counter-transport


  • Na+ – Ca²+
  • Na+ – H+
• Endocytosis


  Active process requiring energy, cell extends processes around substance which becomes enclosed in a food vacuole
• Types of endocytosis


  • Phagocytosis (cell eating)
  • Pinocytosis (cell drinking)

  
• Exocytosis


  Reverse of endocytosis, active process requiring energy, secretory granules or vesicles are extruded out of the cell

  
• Exocytosis


  • Pancreatic cells secrete insulin
  • Neurons release neurotransmitters