Which statement correctly describes enzymes?

Which statement correctly describes enzymes?

• A. Enzymes are stable proteins.
• B. Enzymes are protein catalysts of biological origin.
• C. Enzymes affect the rate of a chemical reaction by raising the activation energy needed for the reaction to take place.
• D. Enzyme activity is not altered by heat denaturation.

Answer: (B)

Enzymes act as biological catalysts, speeding up chemical reactions by lowering the activation energy required to reach the transition state. They are typically proteins with a specific shape and active site that binds substrates, giving each enzyme its selectivity for a particular reaction. This makes the description “protein catalysts of biological origin” the best fit, since it captures both their nature as living, protein-based catalysts and their role in accelerating reactions. The other statements miss key points: enzymes are not always stable under all conditions and can be denatured by heat; they do not raise the activation energy (they lower it to speed up the reaction); and while most are proteins, there are exceptions to consider in more advanced contexts.

Enzymes act as biological catalysts, speeding up chemical reactions by lowering the activation energy required to reach the transition state. They are typically proteins with a specific shape and active site that binds substrates, giving each enzyme its selectivity for a particular reaction. This makes the description “protein catalysts of biological origin” the best fit, since it captures both their nature as living, protein-based catalysts and their role in accelerating reactions. The other statements miss key points: enzymes are not always stable under all conditions and can be denatured by heat; they do not raise the activation energy (they lower it to speed up the reaction); and while most are proteins, there are exceptions to consider in more advanced contexts.