Cell Bio Review Sheet 26-29

Cell Bio Review Sheet 26-29 - Review Sheet for Lectures...

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Review Sheet for Lectures 26-29 Lecture 26 Retrieval of RER enzymes that get into Golgi Why go backwards (retrograde)? -RER proteins that contain the amino acid sequence KDEL (lys, asp,glu,leu) should stay in RER -Some RER enzymes accidentally “escape” to Golgi in COPII vesicles -These enzymes can be retrieved by KDEL receptors in COPI vesicles and returned to RER Clathrin: Moves materials from TGN to lysosomes, endosomes and plant vacuoles. Also from plasma membranes to endosomes COPII: Anterograde from RER COPI: coat proteins for retrograde movement toward RER Lysosomes: Acidic organelles for degredation and recycling The energy of ATP hydrolysis is used to pump H+ into the lysosome This ATPase is an ATP-dependent H+ pump Lysosomal enzyme targeting by Mannose-6-P -An enzyme destined for the lysosome is phosphorylated on a mannose sugar in the cis golgi. -Mannose-6-P receptors in trans golgi bind this protein and packages it into vesicles -Clathrin binds to the outside of these vesicles, targeting them to become lysosomes -The lysosomal enzyme is released from the receptor as the lysosome matures -Clathrin is released and the receptors are recycled to the golgi -Some mannose-6-P receptors that ended up on the plasma membrane are retrieved and recycled. Roles for Lysosomes in Phagocytosis -Particles are brought in by endocytosis -The vesicle formed inside the cell is called a phagosome -Lysosomes fuse with phagosomes and transfer their hydrolytic enzymes inside, creating a phagolysosome -The particle gets digested and nutrients pass into the cytoplasm -The leftover, non-digestible material (garbage) is dumped out from residual bodies by exocytosis. This is where some mannose-6-P receptors can make it to the plasma membrane Role of lysosomes in autophagy Autophagy is a way to get rid of dead organelles such as mitochondria and chloroplasts -An autophagic vesicle is formed by wrapping ER membrane around a dead mitochondria -Lysosomes fuse with this to make a autophagolysosome -The lysosome transfers lytic enzymes into this vesicle and the mitochondria is broken down -The leftovers remain in the residual body until they can be dumped out of the cell by exocytosis Receptor-mediated Endocytosis -Ligands bind to receptors on the outside of the cell. A classic example is LDL (low density lipoproteins) binding to LDL receptors
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This note was uploaded on 09/30/2010 for the course BIO 201 taught by Professor Janicke during the Spring '08 term at SUNY Buffalo.

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Cell Bio Review Sheet 26-29 - Review Sheet for Lectures...

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