MCQs

The cis face, or forming face, is oriented toward the endoplasmic reticulum to intercept emerging transport vesicles.

Plant Golgi bodies are often referred to as dictyosomes because they exist as smaller, dispersed stacks within the plant cytoplasm.

The Golgi apparatus accepts vesicles from the ER, performs biochemical modifications, and targets them to their final cellular destinations.

The active sites of lipid synthesis enzymes face the cytosol, adding new lipid molecules directly to the cytosolic leaflet of the SER.

Ribophorins I and II are structural glycoproteins found uniquely on the RER membrane that secure ribosomes in place during synthesis.

Because COPII vesicles carry cargo forward (anterograde), blocking them causes proteins to pile up within the ER.

Glucose-6-phosphatase is a resident enzyme of the SER membrane, playing a key role in regulating blood glucose levels.

The Sec61 complex forms the physical protein-conducting channel (translocon) across the RER membrane. Blocking it halts co-translational translocation.

BiP (Binding Immunoglobulin Protein) uses ATP to mask exposed hydrophobic regions on nascent proteins, preventing aggregation and helping them fold properly.

New lipids are added to the cytosolic leaflet of the ER. Scramblases flip lipids randomly across leaflets without needing energy, balancing out the bilayer surface area.

The Signal Recognition Particle halts translation temporarily to prevent premature protein folding in the cytosol before docking at the RER translocon.

COPII coatomer proteins assemble transport vesicles moving anterograde from the ER toward the cis-Golgi. COPI tracks retrograde movements.

Transmembrane proteins are threaded into the RER membrane during translation, moving via vesicles through the secretory pathway to reach the plasma membrane.

A core carbohydrate tree is built on dolichol phosphate, a membrane lipid anchor, before being transferred to an asparagine residue of the growing peptide.

The Unfolded Protein Response (UPR) activates signaling loops to expand ER volume, increase chaperone expression, and halt translation to manage stress.

The Lys-Asp-Glu-Leu (KDEL) sequence at the C-terminus of ER-resident proteins ensures they are captured and recycled back if they escape to the Golgi.

The Signal Recognition Particle (SRP) binds the emerging N-terminal signal sequence of a peptide, stalling translation until it docks with the RER membrane.

The sarcoplasmic reticulum is a specialized SER that hoards calcium ions, releasing them into the sarcoplasm to trigger muscle contraction.

The SER contains the Cytochrome P450 enzyme family, which hydroxylates hydrophobic compounds to increase solubility and ease excretion.