Endoplasmic reticulum — structure?
Network of membrane cisternae, tubules, and vesicles
ER continuity — with?
Nuclear envelope and Golgi vesicles
RER — ribosome coverage?
Covered with ribosomes, rough appearance
SER — ribosome coverage?
Lacks ribosomes, smooth appearance
RER membrane — composition?
70% proteins, 30% lipids, low cholesterol, unsaturated phospholipids
RER lumen — contents?
Proteins, BiP, Ca2+, carbohydrates facing lumen
SER membrane — composition?
70% proteins, 30% lipids, low cholesterol, unsaturated phospholipids
SER lumen — contents?
Ca2+ in muscle, steroids in luteal cells
Protein translocation — mechanism?
Signal sequence recognition, SRP binding, docking, co-translational entry
N-glycosylation — process?
Adds 14 sugars to Asn in co-translational manner
Protein folding in ER — role of?
BiP chaperone and PDI enzymes
Disulfide bonds — formation?
Catalyzed by PDI, corrects mispaired bonds
ER quality control — decision?
Properly folded proteins exit, misfolded return for degradation
Phospholipid synthesis — site?
Hyaloplasmic face of SER membrane
Lipid transport — destination?
Mitochondria, peroxisomes, or stored as lipid droplets
Steroid synthesis — key enzyme?
Cytochrome P450 hydroxylates precursors
Steroid precursor?
Cholesterol converted to pregnenolone
Calcium storage — organelle?
Sarcoplasmic reticulum in muscle cells
Calcium release — mechanism?
IP3 or voltage-gated channels
SER detoxification — process?
Cytochrome P450 hydroxylates toxins for solubility
Testez vos connaissances avec un QCM de 20 questions sur Endoplasmic Reticulum Functions and Structure.
1. Which description best characterizes the endoplasmic reticulum in eukaryotic cells?
2. What is a key structural connection of the endoplasmic reticulum?
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