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The enzyme is denatured: the active site changes shape, so the substrate no longer fits and fewer enzyme–substrate complexes form.
Key words: denatured · active site · complementary
Molecules gain kinetic energy, so enzyme and substrate collide more often and more enzyme–substrate complexes form.
Key words: kinetic energy · collisions
Enzymes are protein molecules, not living things; at high temperature they are denatured.
Key words: denatured
The region of an enzyme with a specific shape into which the substrate fits.
Key words: active site · substrate
The temporary structure formed when the substrate binds to the active site.
Key words: complex
The temperature at which an enzyme works fastest (about 37 °C for most human enzymes).
Key words: optimum
The temperature producing the highest measured enzyme activity under specified conditions.
Key words: optimum temperature
Loss of a protein’s functional three-dimensional shape.
Key words: denaturation
Energy an object or particle has because it is moving.
Key words: kinetic energy
A collision with suitable energy and orientation for binding or reaction.
Key words: successful collision
Molecular explanation: Low kinetic energy; fewer successful collisions. Expected effect: Slow rate, usually reversible on warming.
Key words: Low
Molecular explanation: More frequent energetic collisions and complexes. Expected effect: Rate increases.
Key words: Rising towards optimum
Molecular explanation: Highest measured rate under the test conditions. Expected effect: Maximum on the curve, not necessarily 37°C.
Key words: Optimum
Molecular explanation: Interactions stabilising protein shape are disrupted. Expected effect: Active site changes; rate falls as enzyme denatures.
Key words: Above optimum
False. Optima vary among enzymes and organisms and depend on assay conditions.
False. Low temperature usually slows motion and collisions without permanently altering shape.
False. Enzymes are not living; the protein denatures and loses functional shape.
False. That trend holds only until structural disruption outweighs the collision-rate increase.
