Session 9: Organelles 2 Flashcards
Who was the scientist that described the golgi complex and what method did he use?
Camillo Golgi described the layered membrane structures using light microscopy staining
What processing occurs in the golgi complex?
- glycosylation - addition of sugar residues
- production of glycoproteins and proteoglycans
- cleave/fold proteins, glucagon, and other peptide hormones
- proteins that are processed inside the golgi have effects outside the cell
Explain how the golgi processes vesicles delivered from the sER or rER.
- vesicles are going into the cis face and then detach –> go through the golgi and leave through the trans face
- vesicles fuse to cell membrane for secretion OR to fuse to another organelle
How can the secretion be a drug target?
Golgi can fuse a protein-containing vesicle and secrete it out the cell or transport to another organelle (like lysosome)
What type of cytoskeleton is involved with intracellular transport of the golgi complex?
Microtubules (highway) and microfilament motor proteins
What is the function of lysosomes?
Intracellular, enzymatic breakdown of biopolymers
- proteins, nucleic acids, and lipids
- proteases, nucleases, lipases, etc.
How does the structure of lysosomes relate to its function?
single membrane (compartmentalization)
- ACIDIC interior (maintained by ATP-dependent proton pump)
- contains acid hydrolases
- acidic envrionment improves enzymatic function
Name the 4 delivery routes of lysosomes
phagosome - larger particles, bacteria, cell debris, WBC
- cell membrane wraps around bacteria to phagocytose
endosome - small external particles (endocytosis)
autophagosome - normal process of breakdown of damaged cellular structures
- ER wraps around to carry to lysosome (mitochondria)
direct protein import - amino acid targeting seqeunce (KFERQ)
What are the steps of autophogy?
1) initation - membrane (phagophore) and protein from the sER and rER are delivered
2) elongation - membrane of ER, GA, or PM wraps aound the organelles (mitochon, protein, etc)
3) completion - complete fusion of the membrane around; membrane of autophagosome can fuse to membrane of lysosome
4) fusion - autolysosome is formed and lysosomal hydrolases degrade the contents inside
5) release - contents are moved out and can be reused into new biopolymers
What happens when lysosomes are unable to import hydrolytic enzymes (delivery defect)?
Lysosome accumulates undigested material and the contents cannot move on to the next step
- there is no enzyme to breakdown the cargo
possible causes: aa import sequence mutation or mutation in delivery from golgi
If delivery was ok, what disease would result from a mutation of the degradative enzyme? How?
Mutation in the gene encoding the degradative enzyme
–> cannot degrade cargo –> lipid accumulation –> no exocytosis
Explain the cause of Fabry’s lysosomal disease and its therapeutic drug.
Normal: enzyme gets folded into correct shape and participates in lysosomal lipid breakdown.
Fabry’s: mutant enzyme MISfolds in ER –> gets extruded out the ER and degrades –> doesn’t deliver to lysosome
–> lipids accumulate in lysosome –> cell damage
Drug: Galafold
- pharmacological chaperones that binds enzyme, folds to correct shape and regains 3D structure
Describe what peroxisomes are.
SERINE-LYSINE-LEUCINE (PTS)
- single membrane structures that have high concentration of enzymes
- receptors recognize targeting aa sequence on proteins
- delivered via ATP-dependent system
- causes fatty acid beta-oxidation (breakdown)
- produces H2O2
What is the by-product of beta-oxidation?
By-product: H2O2 –> OH
- H2O2 can spontaneously produce hydroxyl radicals (OH)
- radical is very unstable and causes protein/membrane damage
*NEED CATALASES to breakdown H2O2 to prevent radicals from forming
