18 flashcards · Shared on 19 August 2026 by AtomAI Library
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Which statement best describes the structure of most enzymes?
They are globular proteins whose activity depends on their three-dimensional shape
Which statement best describes the structure of most enzymes?
They are globular proteins whose activity depends on their three-dimensional shape
What is an enzyme's active site?
The region where the substrate binds and catalysis occurs
How does the induced-fit model describe substrate binding?
Binding causes the enzyme to change shape slightly, improving the catalytic fit
What is the main effect of an enzyme on a chemical reaction?
It lowers the activation energy by providing an alternative reaction pathway
Which feature of a reaction is not changed by an enzyme?
The equilibrium position between reactants and products
Why is an enzyme usually specific for a particular substrate or group of related substrates?
The active site has complementary shape and chemical properties to its substrate
What is an enzyme–substrate complex?
A temporary association formed when a substrate binds to an enzyme
Why can a high temperature cause an enzyme to lose activity?
It can disrupt interactions maintaining the enzyme's shape and alter the active site
At temperatures below an enzyme's optimum, why does increasing temperature usually increase reaction rate?
Molecules have more kinetic energy, so successful collisions occur more often
How can a large change in pH reduce enzyme activity?
It alters the ionisation of amino acid side chains, affecting bonding and the active site
Why does reaction rate eventually level off as substrate concentration increases while enzyme concentration remains constant?
Most active sites are occupied, so enzyme concentration limits the rate
Which description defines competitive inhibition?
An inhibitor competes with the substrate for the enzyme's active site
How can the effect of a reversible competitive inhibitor often be reduced?
Increase the substrate concentration
What characterises non-competitive inhibition?
The inhibitor binds away from the active site and reduces catalytic activity
Why does adding more substrate not usually overcome non-competitive inhibition?
The inhibitor reduces enzyme function without competing for active-site occupancy
What is irreversible inhibition?
Long-lasting inactivation, often involving very strong or covalent binding to the enzyme
What is a cofactor?
A non-protein component required for the activity of some enzymes
In feedback inhibition, how does the end product of a metabolic pathway regulate the pathway?
It inhibits an enzyme acting earlier in the pathway