BU BIOL 502 - exam 3 notes (64 pages)

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exam 3 notes



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exam 3 notes

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Pages:
64
School:
Binghamton University
Course:
Biol 502 - Biochem:Metabolic Aspects(DIS)
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lecture 26 03 26 2012 Retrieval of RER enzymes that get into Golgi Why go backwards retrograde o RER proteins that contain a a sequence KDEL lys asp glu leu should stay in RER o Some RER enzymes accidentally escape to Golgi in COPII vesicles o These enzymes can be retrieved by KDEL receptors in COPI vesicles and returned to RER o KDEL sequence recognition key that makes it get retrieved back to the RER Can be altered to be forced to leave or go back to RER Lysosome acidic organelle for degradation break down things and recycling Energy of ATP hydrolysis is used to pump H into the lysosome acidify the lumen of lysosome o Can pump H out to make ATP Lysosomal enzyme targeting by Mannose 6 P targets enzyme to go to lysosome o 1 An enzyme destined for the lysosome is phosphorylated on a mannose sugar in the cis golgi Made in the RER o 2 Mannose 6 P receptors in trans golgi bind this protein and package it into vesicles o 3 Clathrin binds to the outside of these vesicles targeting them to become lysosomes o 4 Lysosome enzyme is released from the receptor as the lysosome matures o 5 Clathrin is released and the receptors are recycled to the golgi o 6 Some mannose 6 p that end up on the plasma membrane are retrieved and recycled Some fuse with the plasma membrane lecture 27 03 26 2012 Role of lysosome in phagocytosis 1 Particles are brought in by endocytosis into the cell 2 The vesicle formed inside the cell is called a phagosome 3 Lysosome fuse with phagosomes and transfer their hydrolytic enzymes inside creating a phagolysosome 4 The particle gets digested and nutrients pass into cytoplasm 5 The leftover non digestible material garbage is dumped out from residual bodies by exocytosis out of the cell Role of lysosome in autophagy get rid of dead organelles like mitochondria and chloroplast 1 An autophagic vesicle is formed by wrapping ER membrane around a dead mitochondria 2 Lysosome fuse with this to make an autophagolysosome 3 The lysosome transfer lytic enzymes into this vesicle and the mitochondria is broken down 4 The leftovers remain in the residual body until they can be dumped out of the cell by exocytosis no clathrin on the vesicles Receptor mediated endocytosis 1 Ligand anything that binds to receptors bind to receptors on the outside of the cell A classic example is LDL low density lipoprotein binding to LDL receptor Each receptor has a specific binding to a specific ligand 2 Clathrin binds to the transmembrane receptor and endocytotic vesicles form 3 The clathrin coat is shed the endosome is acidified the ligand is dissociated from the receptor and the rest is sorted into different endosomes and other compartments 4 If the ligand is needed by the cell it is transported to the cytoplasm 5 The receptor is recycled to the plasma membrane 6 If new receptors are needed they are made in the RER and trafficked through the endomembrane system Lysosomal fusion with other membranes 1 Autophagy primarily for degredation of dead mitochondria o mitochondria ER autophagosome lysosome autophagolysosome 2 Phagocytosis bringing in particles such as bacteria from the outside o phagosome lysosome phagolysosome 3 Receptor mediated endocytosis ligand binding stimulates endocytosis o endocytotic vescicle endosome lysosome late endosome autolysosome Where have we seen receptors so far 1 Plasma membrane o A facing outside LDL receptors o B facing inside t SNARES targets vesicle to bind to plasma membrane 2 Cytoplasm soluble receptors importin NLS SRP signal sequence 3 Nuclear membrane nuclear pore filament bind importin or NLS 4 RER o A facing cytoplasm SRP receptor looks for SRP bound to signal sequence o B facing lumen cargo receptors looks for specific cargo to bind so it can bind the proper coat protein 5 Golgi o A facing cytoplasm transmembrane receptor for COPs o B facing lumen mannose 6 P receptors 6 Transition vesicles transmembrane receptors and v SNARES vesicle Cellular reproduction Two main consideration o 1 Nuclear division mitosis not cell division only prepares for cell division by packing DNA o 2 Cell division cytokinesis cell movement cannot happen without mitosis How is DNA replicated for mitosis o Meselson Stahl experiments 1 Grow bacteria on heavy nitrogen N 15 radioactive to metabolically label all newly synthesized DNA 2 Then switch to regular light nitrogen N 14 non radioactive All newly replicated DNA will be light but the old parental DNA will be heavy this way you can tell which DNA is new and which is old N 15 change growth media N 14 3 Use density gradient centrifugation to separate heavy and light DNA They used cesium density gradients instead of sucrose o separation of bacterial DNA by density centrifugation add mix of light heavy and hybrid DNA to cesium density gradient light on top natural normal DNA hybrid on middle heavy on bottom o 3 possibilities for replication of DNA in bacteria 1 Dispersive hybrid in the 1st generation light and heavy 2nd gen same as 1st gen 1 band hybrid 2 Conservative always both heavy and light present no hybrid 2nd gen either heavy or light same as 1st gen 2 bands heavy or light 3 Semi conservative hybrid in the 1st generation but both hybrid and light in the 2nd generation 2nd gen hybrid and light 2 bands hybrid or light o results of meselson stahl 1 Beginning all DNA is heavy 2 1st gen all DNA is hybrid 3 2nd gen there are hybrid and light bands very little of the original DNA left so it cant be seen conclusion bacterial DNA is semi conservative lecture 28 Replication of bacterial circular DNA 03 26 2012 Original strand parental strand or template strand New strand daughter strand Semi conservative DNA replication in eukaryotes Cant use gradient density centrifugation to separate chromatids or DNA from eukaryotes Use metabolically labeled DNA and look at mitotic chromosomes o 1 Must use mitotic cells to see compacted chromatids o 2 Use BrdU bromodeoxyuridine to substitute for thymidine in DNA A T A BrdU o 3 Thymidine stains dark but BrdU doesn t o 4 All T is dark dominant all BrdU is light recessive hybrid is dark light all is BrdU all newly synthesized DNA dark can be all T or hybrid result DNA replication is semiconservative o 1st gen both chromatids contain 1 strand BrdU and 1 strand thymidine hybrid dark o 2nd gen one chromatid is dark hybrid and the other is light in each mitotic chromosome after 2 generations mitotic chromosome is half light half dark 3 strands of BrdU and 1 strand thymidine radioactive thymidine doesn t work


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