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
Answer 20 questions on 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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