C1.1 Enzymes and metabolism

• Enzymes are mostly protein biological catalysts, with some RNA examples

• They work in small amounts and remain unchanged after catalysis

• Metabolism is all enzyme-controlled chemical reactions in cells

• Specific enzymes control which metabolic reactions occur and when

• Anabolism builds complex molecules by condensation and requires energy

• Catabolism breaks molecules by hydrolysis or oxidation and releases energy

• Enzymes are usually globular proteins with a small active-site pocket

• The active site binds substrate, forms an ES complex, and catalyses reaction

• Substrate binding induces shape changes in both enzyme and substrate

• Induced fit aligns catalytic groups and raises substrate toward transition state

• Molecular motion brings substrates and active sites into collision

• Higher kinetic energy increases successful active-site collisions

• Active-site amino acid arrangement determines substrate specificity

• Denaturation changes tertiary structure and active-site shape, not peptide bonds

• Temperature increases rate to an optimum, then denaturation lowers activity

• pH changes active-site bonding; substrate concentration rises to saturation plateau

• Measure substrate loss or product formation per unit time

• Use initial rate, replicates, controls, and graphs from amylase or catalase assays

• Enzymes lower activation energy by providing an alternative pathway

• They stabilize transition states but do not remove the energy barrier