MCQs

One strand runs in the 5' to 3' direction while its complementary partner runs in the 3' to 5' direction.

Retinal links to the opsin protein via a carbon-nitrogen double bond called a Schiff base linkage, which is central to proton-pumping mechanisms.

AGEs are formed via glycation, a chaotic, non-enzymatic reaction where excess blood sugars bind randomly to proteins and lipids, disrupting their function.

MTP is essential for transferring lipids onto the emerging ApoB-100 polypeptide chain; a deficiency in MTP results in the disorder abetalipoproteinemia.

The host immune receptor TLR4 identifies the specific configuration of Lipid A's six fatty acid chains; altering this number prevents effective receptor binding and signaling.

Autoimmune attacks targeting myelin glycolipids or associated proteins disrupt the structural layout of the myelin sheath, impairing nerve signal conduction.

Sialic acid residues carry a negative charge at physiological pH; removing them lowers the cell's negative charge, altering cell-to-cell spacing and interactions.

The dense array of host-derived sugar chains on gp120 creates a structural "glycan shield" that hides underlying viral protein epitopes from the host immune system.

Hyaluronic acid is a massive, unsulfated glycosaminoglycan that serves as the central structural spine for large extracellular proteoglycan complexes.

UDP-GlcNAc synthesis requires glucose, glutamine, acetyl-CoA, and UTP, making its concentrations highly responsive to overall cellular nutrient status.

Tunicamycin blocks the transfer of N-acetylglucosamine-1-phosphate onto dolichol phosphate, halting the assembly of the core sugar chain.

Lipoprotein lipase requires ApoC-II as a co-factor to bind and hydrolyze triacylglycerols within chylomicrons and VLDLs.

Dolichol phosphate is a long, polyisoprenoid lipid molecule embedded in the ER membrane that serves as the membrane anchor for building the core glycan.

Without the phosphotransferase enzyme, lysosomal proteins lack the mannose-6-phosphate tag needed for sorting, causing them to be misdirected and secreted.

PI-PLC specifically hydrolyzes the phosphodiester bond within the GPI anchor, releasing the attached glycoprotein from its lipid tail.

Unmodified or poorly glycosylated proteins fail the ER quality control check, remain bound to chaperones, and are targeted for ER-associated degradation (ERAD).

Heavily glycosylated proteins form a protective sugar shield on the inner lysosomal membrane, protecting the peptide bonds from proteases.

Mucins cross-link via disulfide bonds to form large polymeric networks. Their hydrophilic sugar chains then trap water molecules to form a gel.

HDL acts as a vascular scavenger, picking up free cholesterol from peripheral tissues and transporting it back to hepatic tissues.