Understand the biological catalysts that make life possible with this
comprehensive enzymes and metabolism flashcard deck. Nearly every
chemical reaction inside a living cell — from digesting food to
replicating DNA — is catalysed by a specific enzyme, and...
Understand the biological catalysts that make life possible with this
comprehensive enzymes and metabolism flashcard deck. Nearly every
chemical reaction inside a living cell — from digesting food to
replicating DNA — is catalysed by a specific enzyme, and metabolism is
the sum of all these reactions working together to sustain life.
This deck covers enzyme structure and the active site, the lock-and-key
and induced-fit models, activation energy, factors affecting enzyme
activity (temperature, pH, substrate concentration), competitive and
non-competitive inhibition, cofactors and coenzymes, Michaelis-Menten
kinetics, and the basics of catabolism and anabolism. Essential for
GCSE, A-Level, AP Biology, and university biochemistry courses.
Ready to test yourself?
Flip through all 30 cards in interactive study mode.
A biological catalyst (usually a protein) that speeds up a specific reaction without being consumed.
The minimum energy needed to start a reaction; enzymes lower it by stabilizing the transition state.
The region where substrate binds, shaped by the enzyme's tertiary structure — gives specificity.
Active site has a fixed shape exactly matching the substrate, like a key fitting a lock.
The active site is flexible and moulds slightly around the substrate as it binds.
The temporary structure formed when substrate binds the active site, lowering activation energy.
Increases to an optimum, then denatures beyond it, destroying the active site.
Each enzyme has an optimum pH; deviation disrupts bonds and alters active site shape.
Rate rises until all active sites are saturated (Vmax), then plateaus.
Rate increases proportionally, provided substrate is in excess.
Irreversible loss of protein 3D structure from heat/pH/heavy metals, destroying the active site.
A non-protein chemical component (often a metal ion like Zn²⁺, Mg²⁺, or Fe²⁺) required by an enzyme to become catalytically active; an enzyme without its cofactor is called an apoenzyme.
An organic cofactor, usually derived from a vitamin, that helps enzymes catalyze reactions by carrying chemical groups between them (e.g., NAD⁺, FAD, Coenzyme A).
When an inhibitor molecule resembles the substrate and binds directly to the active site, blocking the substrate from binding; can be overcome by increasing substrate concentration.
When an inhibitor binds to a site other than the active site (an allosteric site), changing the enzyme's shape so it can no longer bind substrate effectively; increasing substrate concentration does not reverse it.
Control of enzyme activity through molecules binding at a site distinct from the active site, causing a conformational change that increases or decreases catalytic activity.
A regulatory mechanism where the end product of a metabolic pathway inhibits an enzyme earlier in that same pathway, preventing overproduction of the product.
The relationship between reaction rate (v) and substrate concentration ([S]) for many enzymes: v = (Vmax[S]) / (Km + [S]).
High substrate affinity — the enzyme reaches half its maximum reaction rate at a low substrate concentration, meaning it binds substrate efficiently.
The maximum reaction rate achieved when an enzyme is fully saturated with substrate.
The complete set of chemical reactions that occur within a living organism to maintain life, including breaking down and building up molecules.
The metabolic breakdown of complex molecules into simpler ones, typically releasing energy (e.g., digestion, cellular respiration).
The metabolic building of complex molecules from simpler ones, typically requiring energy input (e.g., protein synthesis, DNA replication).
Because it stores energy in its phosphate bonds and releases it readily when hydrolyzed, powering most cellular processes across nearly all organisms.
A series of linked, enzyme-catalyzed chemical reactions occurring within a cell, where the product of one reaction becomes the substrate for the next (e.g., glycolysis, the Krebs cycle).
Intracellular enzymes act inside the cell that produced them (e.g., enzymes in respiration); extracellular enzymes are secreted out of the cell to catalyze reactions externally (e.g., digestive enzymes).
Reversible inhibitors (competitive or non-competitive) bind temporarily and can dissociate, restoring activity; irreversible inhibitors bind permanently (often covalently), permanently disabling the enzyme (e.g., nerve agents on acetylcholinesterase).
Amylase breaks starch into maltose; protease (e.g., pepsin) breaks proteins into peptides; lipase breaks fats into fatty acids and glycerol.
The precise three-dimensional shape of the active site, which fits only one or a few specific substrate molecules, following the lock-and-key or induced-fit model.
Because all available active sites become saturated with substrate, so the rate reaches Vmax and enzyme concentration — not substrate — becomes the limiting factor.
