Class XI Biology: Power of Enzymes

Vocabulary practice flashcards covering fundamental enzyme kinetics, mechanisms of action, environmental factors, inhibition modes, immobilisation methods, and industrial biotechnology applications from Class XI Biology.

Enzyme

A protein produced by a living organism that acts as a biological catalyst in a chemical reaction by reducing activation energy.

Intracellular Enzymes

Enzymes that operate inside cells, vital for cell metabolism and survival by catalysing reactions such as cellular respiration, protein synthesis, DNA replication, and detoxification.

Extracellular Enzymes

Enzymes secreted by cells that catalyse reactions outside the cell, such as digestive enzymes in the gut or fungal enzymes secreted to digest external food.

Active Site

An area on an enzyme molecule where the substrate can bind, formed by the precise three-dimensional folding of the globular protein.

Substrate

A specific molecule upon which an enzyme acts.

Enzyme-Substrate Complex

The temporary molecular structure formed when a substrate molecule binds to the active site of an enzyme and is held by temporary bonds with R groups of the enzyme's amino acids.

Lock-and-Key Hypothesis

A hypothesis for enzyme action stating that the substrate has a shape complementary to the enzyme's active site and fits into it exactly, demonstrating enzyme specificity.

Induced-Fit Hypothesis

A modified hypothesis proposed in 1959 stating that the substrate is complementary in shape to the active site, but the enzyme (and sometimes the substrate) alters its shape slightly upon entry to achieve a perfect fit and maximise catalytic efficiency.

Activation Energy

The energy that must be provided to make a chemical reaction take place; enzymes accelerate reaction rates by decreasing this energy barrier.

Lysozyme

An antibacterial enzyme found in tears, saliva, and secretions that catalyses the hydrolysis of polysaccharide chains in bacterial cell walls, causing bacteria to lyse via osmotic influx.

Initial Rate of Reaction

The rate of an enzyme-controlled reaction measured at the very start (represented by the steepest slope of the progress curve near time zero), before substrate depletion causes the reaction to slow.

Colorimeter

An instrument that quantitatively measures the colour intensity of a solution by measuring the absorption of specific wavelengths of light.

Optimum Temperature

The specific temperature at which an enzyme catalyses a reaction at its maximum possible rate (typically around $40^\circ\text{C}$ for most human enzymes).

Denaturation

The irreversible loss of an enzyme's precise three-dimensional shape and catalytic activity caused by extreme temperatures or pH, which disrupt hydrogen and ionic bonds holding the tertiary structure intact.

Buffer Solution

A solution of a specific pH that resists changes in hydrogen ion concentration, maintaining a stable pH even when an ongoing chemical reaction produces acidic or basic substances.

$$V_{\max}$$

The theoretical maximum rate of an enzyme-controlled reaction, achieved when all enzyme active sites are fully saturated with substrate.

Michaelis-Menten Constant ($K_m$)

The substrate concentration at which an enzyme functions at half of its maximum velocity ($\frac{1}{2}V_{\max}$); it serves as an inverse measure of the enzyme's affinity for its substrate.

Competitive Inhibition

A type of reversible enzyme inhibition in which an inhibitor structurally similar to the normal substrate competes directly for binding at the active site; the inhibition can be overcome by increasing substrate concentration.

Non-Competitive Inhibition

A type of reversible enzyme inhibition where an inhibitor binds to a region other than the active site, disrupting internal bonding and altering the active site's shape so substrates cannot fit; cannot be overcome by increasing substrate concentration.

End Product Inhibition

A negative feedback mechanism in metabolic pathways where the final product reversibly binds as a non-competitive inhibitor to the first enzyme in the pathway, regulating product concentration within narrow physiological limits.

Immobilised Enzymes

Enzymes that are chemically or physically attached to an inert support surface or trapped inside matrices such as alginate beads or agar gel, preventing them from diffusing freely.

Alginate Beads

Small gel-like beads produced from sodium alginate (a seaweed extract) and calcium chloride used to encapsulate enzymes, allowing substrates to enter and products to leave while facilitating enzyme recovery and preventing product contamination.

Cellulase

An enzyme used industrially to hydrolyse cellulose found in plant cell walls into simple glucose molecules, which can subsequently be fermented to produce bioethanol.

Glucose Isomerase

An immobilised enzyme used in the pharmaceutical and food industries to convert glucose into fructose to manufacture high-fructose syrup.

Insulin

A peptide hormone that lowers blood glucose levels by promoting glucose conversion into glycogen; industrially synthesised by recombinant microorganisms such as genetically modified Escherichia coli and Saccharomyces cerevisiae.

Mycoprotein

A high-protein, low-fat food product derived from the fungal biomass of Fusarium venenatum, produced via aerobic fermentation and utilised as a sustainable meat substitute.

Penicillin

An antibiotic produced during industrial fermentation of the fungus Penicillium chrysogenum using the enzyme isopenicillin N synthase (IPNS) to construct its core structure.

Pectinase

An enzyme sourced from microorganisms such as Aspergillus, Penicillium, or Bacillus species that hydrolyses pectin in fruit cell walls to decrease viscosity, clarify fruit juice, and enhance extraction yield.