Flashcard: Endoplasmic Reticulum Functions and Structure — 20 carte

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