Endocytosis  &  Exocytosis    

Central  ques4on:  

 How  do  molecules  that  are  too  large  to  pass  through  the  plasma  membrane  or  integral  

membrane  proteins  get  into  or  out  of  the  cell?    

Endocytosis  Exocytosis    

Endocytosis    

The  process  by  which  a  molecule  gets  into  a  cell  without  passing  through  the  membrane    Three  types:  -­‐Phagocytosis  -­‐Pinocytosis  -­‐Receptor  mediated  endocytosis  

Phagocytosis:  The  process  by  which  a  cell  ingests  other  cells  or  par4cles  

Phagocytosis    

The  process  by  which  a  cell  ingests  other  cells  or  par4cles    1.  Phagocyte  moves  towards  the  par4cle  2.  The  par4cle  binds  to  surface  receptors    3.  The  par4cle  is  engulfed  by  the  phagocyte,  pinches  off,  

and  forms  a  vacuole    [Possible]  Lysosomes  fuse  with  the  vacuole  and  release  diges4ve  enzymes.  The  digested  materials  are  released  via  exocytosis        

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Pinocytosis:  OMen  thought  of  as  “cell  drinking”.  The  process  by  which  a  cell  takes  

in  fluids  and  dissolved  materials  

Pinocytosis    

The  process  by  which  a  cell  takes  in  fluids  and  dissolved  materials    1.  The  cell  forms  an  invagina4on  and  whatever  

is  in  the  area  is  brought  into  the  cell  2.  The  cell  pinches  off  the  plasma  membrane  

and  forms  a  vacuole    

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Receptor  mediated  endocytosis:  Specific  molecules  are  brought  into  

the  cell  via    receptor-­‐ligand  interac4on  

Receptor  mediated  endocytosis  

Specific  molecules  are  brought  into  the  cell  via    receptor-­‐ligand  interac4on    1.  Par4cles  bind  to  receptors  that  are  clustered  

together  on  the  plasma  membrane  2.  Once  enough  par4cles  bind,  the  cell  

internalizes  the  material  and  forms  a  vacuole  

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Exocytosis    

Exocytosis:  The  process  by  which  intracellular  materials  are  released  to  

the  extracellular  environment  

Exocytosis    

The  process  by  which  intracellular  materials  are  released  to  the  extracellular  environment    1.  Intracellular  vesicles  move  to  the  plasma  

membrane  2.  Vesicle  fuses  with  plasma  membrane  3.  Vesicle  releases  its  contents  to  the  extracellular  

environment  

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