Practice Questions

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.

Cisternae are the flattened fluid-filled sacs making up the ER and Golgi. Cristae belong to mitochondria, and thylakoids belong to chloroplasts.

The smooth endoplasmic reticulum (SER) lacks ribosomes and contains the specialized enzymatic machinery necessary for lipid and steroid metabolism.