GATE XL key terms

The substrate concentration at which an enzyme works at half its maximum velocity. A small Km means the enzyme binds substrate tightly and reaches saturation quickly.

The number of substrate molecules one enzyme molecule converts to product per unit time when fully saturated. It measures catalytic efficiency independent of substrate concentration.

A double-reciprocal graph of 1/velocity against 1/substrate concentration. Its intercepts and slope give Km and Vmax, and the pattern of change reveals the type of inhibition.

Reduction of enzyme activity by a molecule that blocks catalysis. Competitive inhibitors raise apparent Km, while non-competitive inhibitors lower Vmax; the distinction is diagnostic of binding site.

Control of enzyme activity by a molecule binding at a site away from the active site, changing enzyme shape and affinity. It produces sigmoidal kinetics instead of the usual hyperbolic curve.

The ten-step cytosolic pathway that converts one glucose into two pyruvate molecules, producing ATP and NADH. It is the first stage of cellular respiration in nearly all organisms.

ATP synthesis driven by electron transfer through the respiratory chain, which pumps protons and creates a gradient used by ATP synthase. It occurs in the inner mitochondrial membrane.

The combined electrical and pH gradient across a membrane that stores energy. It drives ATP synthesis and solute transport in mitochondria, chloroplasts, and bacteria.

The principle that a proton gradient across a membrane links electron transport to ATP synthesis. Proposed by Peter Mitchell, it explains energy conversion in mitochondria and chloroplasts.

The synthesis of glucose from non-carbohydrate precursors such as lactate, glycerol, and amino acids. It shares most glycolytic enzymes but uses four bypass reactions in liver and kidney.

The semiconservative copying of a DNA double helix, producing two identical duplexes. It requires a template, primers, polymerase, and proofreading to maintain genome fidelity.

Synthesis of an RNA molecule from a DNA template by RNA polymerase. In eukaryotes it is regulated by promoters, enhancers, and transcription factors and is followed by RNA processing.

The ribosome-directed assembly of a polypeptide chain using messenger RNA as the template and transfer RNA to deliver amino acids according to the genetic code.

A cluster of genes transcribed together from a single promoter and regulated as one unit. The lac and trp operons are classic examples of inducible and repressible control.

An in vitro method that amplifies a specific DNA segment through repeated cycles of denaturation, primer annealing, and extension by a thermostable polymerase. It is central to molecular diagnostics and cloning.

Patterns of trait transmission governed by segregation of alleles and their independent assortment during gamete formation. Deviations reveal linkage, epistasis, or non-Mendelian phenomena.

The condition in which allele and genotype frequencies in a population remain constant across generations absent mutation, migration, selection, or drift. It provides a null model for population genetics.

Random change in allele frequencies due to sampling of finite populations. Its effects are strongest in small populations and can fix or eliminate alleles regardless of fitness.

An enzyme that cuts DNA at a specific recognition sequence, often leaving sticky ends. These enzymes are fundamental tools for cloning and restriction mapping.

A technique in which digested DNA fragments are separated by electrophoresis, transferred to a membrane, and detected with a labelled probe. It identifies specific sequences and fragment sizes.

An enzyme-linked immunosorbent assay that detects antigens or antibodies using enzyme-tagged reagents and a colour-producing substrate. Variants include direct, indirect, sandwich, and competitive formats.

An antibody produced by a single cloned B-cell line, giving identical specificity for one epitope. It is used in diagnostics, therapy, and affinity purification.

A thermodynamic potential whose change at constant temperature and pressure predicts spontaneity. Negative change indicates a favourable process; zero indicates equilibrium.

The change in free energy when one mole of a substance is added to a system at constant temperature and pressure. Differences drive diffusion, phase change, and reaction.

A measure of the number of accessible microstates and of energy dispersal in a system. It always increases for the universe in any spontaneous process.

An expression relating rate constant to temperature through an exponential factor containing activation energy. It explains why reaction rates rise steeply with heating.

The minimum energy that colliding molecules must possess for a reaction to proceed. Catalysts lower it without altering the overall free-energy change.

A rule stating that a system at equilibrium shifts to oppose a change in concentration, pressure, or temperature. It predicts the direction of shift but not its magnitude.

The amount of strong acid or base a solution can absorb per unit pH change. It is greatest near the pKa of the buffering species and depends on concentration.

A relation linking pH to the pKa of an acid and the ratio of conjugate base to acid concentrations. It is used to design buffers and interpret titration curves.

The statement that absorbance is proportional to concentration, path length, and molar absorptivity. It underlies colorimetric assays and spectrophotometric quantitation.

A separation method based on differential partitioning of solutes between a mobile phase and a stationary phase. Variants include gel filtration, ion exchange, and affinity modes.

Sodium dodecyl sulfate polyacrylamide gel electrophoresis separates proteins mainly by molecular mass after denaturation. It is used to assess purity and estimate subunit size.

The pH at which a molecule carries no net charge. At this pH a protein does not migrate in an electric field and is least soluble.

A range of values, computed from sample data, expected to contain the true parameter with a stated probability over repeated sampling. Width reflects variability and sample size.

A formal procedure comparing observed data to a null model. It yields a p-value and a decision about rejecting the null, with risks of type I and type II error.

Fitting a straight-line model to relate a response variable to one or more predictors by least squares. It provides slope estimates, predictions, and residual diagnostics.

The proportion of variance in a response variable explained by a fitted model, denoted R-squared. It ranges from zero to one and rises with added predictors.

A measure of the spread of values around their mean, equal to the square root of variance. It carries the same units as the data and is widely used in error analysis.