BIO NMDCAT

The membrane network of the endoplasmic reticulum shares physical continuity with the outer nuclear membrane, allowing structural integration.

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

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

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

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

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

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

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

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

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

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

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

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

Euchromatin is the loosely packed, accessible form of DNA where RNA polymerase can readily bind to transcribe structural genes.

Exportins recognize cargo proteins tagged with an NES and form a complex with Ran-GTP to migrate out of the nucleus.

Because mRNA is kept away from ribosomes during synthesis, the cell can safely carry out splicing and capping before protein translation starts.

High protein synthesis demands rapid ribosome production, which directly causes the hypertrophy of the nucleolus to produce rRNA.