Question
Which of the following statements is true about enzymes?
A. Enzymes are the building blocks for the cell's cytoskeleton.
B. An enzyme reduces the amount of energy needed to convert a substrate into product.
C. Enzymes are metals that act as non-carbon-based catalysts.
D. Enzymes are vitamins that prevent disease.
E. Enzymes cause reactions to occur in cells because they raise the temperature of the cells.
Answer
Correct answer: B. An enzyme speeds a reaction by lowering its activation energy, often by binding substrates and stabilizing the transition state. That lower barrier lets more substrate molecules reach the transition state at the same temperature.
The other statements are false:
- A: Cytoskeletal building blocks include proteins such as actin and tubulin; that is not the defining role of enzymes.
- C: Enzymes are biological catalysts, usually proteins. Some enzymes require metal-ion cofactors, but the enzyme itself is not simply a metal.
- D: Some coenzymes are derived from vitamins, but enzymes are not vitamins.
- E: Enzymes do not catalyze reactions by heating the cell. They provide a lower-activation-energy pathway.
Lowering activation energy changes reaction rate, not the overall free-energy difference between reactants and products and not the equilibrium position.
Evidence boundary
This answer applies only to the A–E option set in UC San Diego Biology 100 Quiz 1, Form 2, Question 12. In option B, amount of energy needed is interpreted precisely as activation energy. Cofactors and coenzymes do not make options C or D correct.
Sources
These references support the concepts and methods used in the explanation above.