Enzymes – Biosciences I (CH4006)

Vocabulary flashcards covering fundamental terms and concepts from the CH4006 Enzymes lecture, including enzyme structure, mechanisms, kinetics, regulation, and their roles in metabolic pathways.

Enzyme

A biological catalyst, usually a globular protein, that speeds up biochemical reactions without being consumed.

Substrate

The specific reactant molecule upon which an enzyme acts.

Active Site

The region of an enzyme where the substrate binds and catalysis occurs.

Enzyme–Substrate Complex (ES)

Temporary association formed when a substrate binds to an enzyme’s active site.

Activation Energy (EA)

The energy barrier that must be overcome for a reaction to proceed; lowered by enzymes.

Lock-and-Key Model

Early model proposing that the enzyme’s active site is an exact fit for the substrate.

Induced Fit Model

Modern model in which substrate binding causes a conformational change that tightens enzyme–substrate interaction.

Anabolic Reaction

Metabolic pathway that builds complex molecules from simpler ones and consumes energy.

Catabolic Reaction

Metabolic pathway that breaks down complex molecules into simpler ones and releases energy.

Dehydration Synthesis

An anabolic process that joins molecules by removing water; catalysed by enzymes.

Hydrolysis

A catabolic process that splits molecules by adding water; catalysed by enzymes.

Globular Protein

Compact, spherical protein type; most enzymes belong to this class.

Substrate Specificity

The property that each enzyme catalyses only one (or a few) particular reactions.

Cofactor

Inorganic ion (e.g., Zn²⁺, Fe²⁺) required for some enzymes to function.

Coenzyme

Organic, non-protein molecule (often a vitamin derivative) that assists enzyme activity.

Prosthetic Group

A cofactor or coenzyme tightly and permanently bound to an enzyme.

Michaelis–Menten Equation

v = (Vmax·[S]) / (Km + [S]); describes the relationship between reaction rate and substrate concentration.

Vmax

The maximum reaction rate achieved by an enzyme at saturating substrate concentration.

Km

Substrate concentration at which reaction rate is half of Vmax; indicator of enzyme affinity.

Competitive Inhibitor

Molecule that resembles the substrate and competes for binding at the active site.

Non-Competitive Inhibitor

Molecule that binds to an allosteric site, altering enzyme shape and reducing activity regardless of substrate concentration.

Irreversible Inhibitor

Substance that covalently binds to an enzyme, permanently inactivating it.

Allosteric Site

Regulatory site on an enzyme, distinct from the active site, where modulators bind.

Phosphorylation (of Enzymes)

Covalent addition of a phosphate group that can activate or deactivate enzymes.

Metabolic Pathway

Series of enzyme-catalysed reactions converting a starting molecule to an end product.

Feedback Inhibition

Regulatory mechanism where an end product acts as an allosteric inhibitor of an early pathway enzyme.

Optimum Temperature

The temperature at which an enzyme’s activity is highest before denaturation occurs.

Optimum pH

The pH value at which an enzyme exhibits maximal catalytic activity.