BIO NMDCAT

In covalent catalysis, a powerful nucleophilic R-group in the active site (e.g., the -SH of cysteine or -OH of serine) forms a transient covalent bond with the substrate. This acyl-enzyme intermediate is then resolved by another step, releasing the product and regenerating the free enzyme.

Allosteric regulation is mediated by modulator molecules that bind to a site (allosteric site) physically distinct from the active site. This binding causes a conformational change that can either increase (allosteric activator) or decrease (allosteric inhibitor) the activity of the enzyme at its active site.

The definition of competitive inhibition is a "competition" for the active site. At a high enough concentration, the substrate out-competes the inhibitor for the active site, so all enzyme molecules can still bind substrate and reach Vmax. The apparent Km is increased, but Vmax is ultimately unchanged.

The amino-terminal ends of both the light (VL) and heavy (VH) chains form the antigen-binding site. These variable domains have highly diverse amino acid sequences from one antibody clone to another, creating a unique 3D surface that is specific for a single epitope.

Saponification is the base-catalyzed hydrolysis of the ester bonds in a fat or oil. This reaction cleaves the triglyceride, producing glycerol and the salts of the fatty acids (soaps). Lipases perform an analogous enzymatic hydrolysis.

Kinases are a class of transferase enzymes that catalyze the transfer of a γ-phosphate group from a high-energy donor molecule like ATP to a specific substrate. Protein kinases phosphorylate specific serine, threonine, or tyrosine residues on target enzymes, regulating their activity. Phosphatases reverse this.

When glucose forms a ring, carbon 1 becomes an asymmetric carbon (the anomeric carbon). In the α-anomer, the -OH on C1 is below the plane of the ring (trans to the CH2OH at C5). In the β-anomer, the -OH is above the plane of the ring (cis to the CH2OH).

Amylose is a linear polymer of glucose with α-1,4 linkages. Amylopectin is a much larger, branched polymer that has both α-1,4 linkages in the straight chain and α-1,6 glycosidic bonds at the branch points approximately every 24-30 glucose units.

On a double-reciprocal plot, a non-competitive inhibitor produces a line that intersects the control line at the x-axis (Km is unchanged), but has a steeper slope and a higher y-intercept (Vmax is decreased). It reduces the number of functional enzyme molecules.

A competitive inhibitor competes for the active site, effectively making it harder for the enzyme to bind its substrate. More substrate is required to reach half the maximum velocity. Therefore, the apparent Km (substrate concentration at 1/2 Vmax) is increased in the presence of a competitive inhibitor.

Secondary structures are defined by the pattern of hydrogen bonds between the carbonyl oxygen (C=O) and the amide hydrogen (N-H) of the peptide backbone itself. The R-groups are not involved; their interactions define the higher-level tertiary structure.

Uracil is a pyrimidine base found in RNA. Like thymine (its counterpart in DNA), its structure is complementary to adenine, and it forms two hydrogen bonds with adenine during base pairing. Guanine pairs with cytosine.

While all levels contribute, the precise 3D shape of an antigen-binding pocket is a feature of the protein's tertiary structure. It is formed by the folding and precise juxtaposition of R-groups from different parts of a single polypeptide chain (in heavy and light chains).

Active transport is the movement of molecules against a concentration gradient. This process is directly coupled to ATP hydrolysis as an energy source, for example, by the Na⁺/K⁺ pump. Passive processes like diffusion and facilitated diffusion are driven by the gradient itself and do not require ATP directly.

A phospholipid is a substituted triglyceride. Lecithin (phosphatidylcholine) consists of glycerol esterified to two fatty acids and a phosphate group, which is in turn esterified to the nitrogenous alcohol choline. Complete hydrolysis breaks all these ester bonds.

Linoleic acid (omega-6) and α-linolenic acid (omega-3) are essential fatty acids. Humans and other mammals lack the enzymes (Δ12 and Δ15 desaturases) to insert double bonds at the required positions in the fatty acid chain. They must be ingested in the diet to maintain health.

The conformational change in the induced fit model positions the essential catalytic amino acid side chains in the precise orientation needed to perform chemistry on the substrate. This is in addition to the strain and proximity effects also associated with the model.

The enzymes responsible for the synthesis of phospholipids (the major membrane lipid) and steroids (including cholesterol and steroid hormones) are located primarily in the membrane of the smooth ER. It is therefore a major site of lipid biosynthesis.

Water's dipole nature (O is δ-, H is δ+) allows it to form hydrogen bonds with and dissolve other polar and charged molecules. It forms hydration shells around these molecules (like sugars and amino acids), effectively separating them from their crystal lattice and bringing them into solution.