BIO NMDCAT

A gene is the fundamental structural and functional unit of heredity, consisting of a nucleotide sequence that carries the code for a protein.

The 5' end of a DNA or RNA strand terminates in a phosphate group attached to the 5' carbon of the pentose sugar.

Adenine (a purine) always pairs with thymine (a pyrimidine) using two hydrogen bonds in standard Watson-Crick base pairing.

The double helix maintains a constant width of 2 nm (20 A˚) because a double-ringed purine always pairs with a single-ringed pyrimidine.

Phosphodiester bonds covalently link the 3' carbon of one deoxyribose sugar to the 5' carbon of the adjacent sugar via a phosphate group.

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

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.

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.

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

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.

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

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

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

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

Without N-linked oligosaccharide chains, nascent polypeptides inside the ER lumen cannot fold properly, triggering the unfolded protein response.

LHCs are pigment-protein chromoprotein complexes where chlorophylls and carotenoids are precisely bound to a protein matrix to capture light.

The dense, charged sugar chains of the lipopolysaccharide layer form a hydrophilic shield that resists the entry of hydrophobic toxic compounds.

Unlike template-driven translation, carbohydrate assembly depends on local enzyme concentrations and kinetics, resulting in glycan variations.

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