Enzymes are described as biological catalysts because they
Correct answer: D. speed up reactions by lowering the activation energy and are recovered unchanged
- A. are used up in the reactions they catalyse
- B. raise the activation energy of a reaction
- C. supply energy to drive unfavourable reactions
- D. speed up reactions by lowering the activation energy and are recovered unchanged
Explanation
An enzyme provides an alternative pathway with a smaller energy barrier, so a far larger proportion of collisions are effective at body temperature, and it emerges from each cycle ready to work again. It cannot make an energetically unfavourable reaction happen, only accelerate one that is already possible. A single enzyme molecule may convert thousands of substrate molecules per second.
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About Enzymes as Biocatalysts
Enzymes are protein or RNA biocatalysts that lower activation energy without being consumed, and their active sites bind specific substrates. The topic covers the lock and key and induced fit models, effects of temperature, pH and substrate concentration, cofactors, enzyme specificity, and competitive versus non-competitive inhibition.
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