AP Syllabus focus:
‘Extreme temperature, pH, or chemical conditions can denature enzymes, disrupting structure and preventing them from catalyzing reactions.’
Enzymes depend on precise 3D shape to function. Temperature, pH, and certain chemicals can disrupt the weak interactions that maintain that shape, reducing reaction rate or stopping catalysis entirely.
Core idea: denaturation stops catalysis
Enzymes are proteins whose function depends on structure at multiple levels (especially tertiary structure). When environmental conditions disrupt stabilising interactions, the enzyme’s shape changes and catalytic activity falls.
Denaturation: A structural change in a protein that disrupts its native folding (and thus function), typically by breaking noncovalent interactions; severe denaturation can also disrupt disulfide bonds.
Practice Questions
FAQ
Their amino acid compositions shift the $pK_a$ values and stability of key residues.
Local environments and stabilising salt bridges can favour unusual charge states.
They can coordinate strongly with side chains (especially thiol groups), creating abnormal cross-links.
This distorts folding and can block catalytic residues.
Detergents surround hydrophobic regions, weakening the hydrophobic effect that drives proper folding.
Unfolded proteins often aggregate or lose the correct active conformation.
Activity can fall from subtle active-site charge/shape changes without global unfolding.
Full denaturation implies broader loss of native folding across the protein.
They adjust internal pH/ion balance and produce protective molecules.
They may increase expression of stabilising proteins (e.g., chaperones) to support correct folding.
