Honors Biology Active and Passive Transport

Active Transport

• Movement of substances from low concentration to high concentration or against the concentration gradient/ electrochemical gradient.  

• ATP supplies the energy needed for active transport

• Usually done by a carrier protein or protein pump.

  • Antiport: moves molecules in opposite directions

  • Symport: moves molecules in one direction across the membrane

Types of Active Transport

• Primary Active Transport

  • directly uses a source of chemical energy to move molecules against their gradient 

    • Ex) Na/K pump

• Secondary Active Transport: uses an electrochemical gradient – generated by active transport – as an energy source to move molecules against their gradient.

  • Does not directly require ATP

  • Also referred to as cotransport

NA/K Pump

• One of the most important pumps in animal cells by maintaining correct concentrations of Na+ and K+ in living cells. 

• Plays a major role in generating voltage across the cell membrane

  • Electrogenic pump 

• Moves 3 Na+ out of the cell and 2 K+ into the cell

Bulk Transport- requires energy 

• Exocytosis

  • Cell secretes biological molecules by fusing vesicles with the plasma membrane 

    • Vesicle typically comes from the Golgi apparatus Cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane. 

• 3 types of endocytosis 

  • Phagocytosis 

  • Pinocytosis 

  • Receptor-mediated endocytosis