BICD 110 Lecture Notes - Lecture 6: Gtpase, Atp Hydrolysis, Copii
28 Jun 2018
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BICD110 Lecture 6 Notes 4/19/18
- Polarized cells: organized in structure in which the outside faces a different environment
than the inside
oEx: pancreatic acinar cell secretes digestive enzymes from one end of the cell (the end
facing the tubule) to the gut
oPolarized cells have polarized organization of their secretory pathway organelles
Specialized organization allowed George Palade to work out the rules of the
secretory pathway. 85% of proteins in this cell are secreted. Few cytosolic proteins
present, so could accurately follow secretory pathway. ER -> Golgi -> zymogen
granules. Radioactively labeled proteins moved over time through this pathway
- More typical cell isn’t polarized; Typically has ER that is a network throughout the cell
oLattice structure; always have a place in the cell not far from the ER (pervasive,
everywhere)
oGolgi located in place in the cell
oER structure continuously changing to form network. Microtubules pull and fuses to
create more junctions within the ER
- ER functions
o1) source of most integral membrane proteins
o2) source of all secreted proteins
o3) source of ER, Golgi, and lysosomal resident proteins: these are the proteins that stay
in these structures that do modifications to other proteins/molecules
o4) source of most lipid synthesis
o5) storage site for Ca++
o6) protein folding. Ex: disulfide isomerase forms disulfide bonds to help stabilize
structures
o7) initial glycosylation (of secreted, membrane, and resident proteins)
o8) quality control: proteins that are shaped checked to make sure they’re good quality
- 2 kinds of ER
orough ER = RER = ER studded with ribosomes
osmooth ER = SER = ER devoid of ribosomes
oall cells have lots of RER, but very little SER is most cells
osome specialized cells have lots of SER
in muscle cells, SER is the sarcoplasmic reticulum, and provides/secretes Ca++ into
muscle fibers to signal muscle contractions
in liver cells, SER makes LDL particles and cholesterol
in liver cells, SER contains many enzymes for detoxifying lipid-soluble drugs
ex: lipid-soluble drugs like phenobarbital or some carcinogens cause
amplification of amount of SER. SER enzymes cytochrome-p450 detoxify drugs by
rendering them water-soluble (adds -OH on hydrophobic drug and washes them
out of your body)
in testis, ovary, and adrenal gland, the SER is the site of steroid hormone synthesis
- Secretory pathway
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