MCQs

While N-linked glycosylation begins in the ER, O-linked glycosylation occurs exclusively within the compartments of the Golgi apparatus.

The cisternal maturation model states that cis-cisternae physically mature into medial and then trans-cisternae, receiving recycling enzymes from behind via COPI vesicles.

Golgi apparatus stacks (dictyosomes) synthesize non-cellulosic polysaccharides and send secretory vesicles to form the phragmoplast and cell plate.

COPI-coated vesicles handle retrograde vesicle transport, moving materials backward from the Golgi to the ER.

Primary lysosomes emerge as transport vesicles from the trans-Golgi network carrying concentrated mixtures of active hydrolytic enzymes.

Lysosomal enzymes are specifically modified with a mannose-6-phosphate (M6P) tag in the cis-Golgi, which is recognized by M6P receptors in the trans-Golgi for sorting.

As proteins move from the cis to the trans face, their attached sugar groups undergo sequential enzymatic modifications to form mature complex glycoproteins.

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.