Enzymes lower activation energy

Steps:

• Recall that enzymes are proteins acting as biological catalysts in reactions.
• Understand catalysts speed up reactions by reducing activation energy, the energy barrier to start the reaction.
• Evaluate each option: check if it correctly defines enzymes as biological catalysts that decrease activation energy.
• Eliminate options that misstate enzyme nature or activation energy effect.

Why A is correct:

• Enzymes are biological catalysts that lower activation energy, allowing reactions to proceed faster without being consumed, per the catalyst definition in biochemistry.

Why the others are wrong:

• B: Enzymes decrease, not increase, activation energy to accelerate reactions.
• C: Enzymes are proteins, not compounds of transition elements like metal catalysts.
• D: Enzymes are neither transition element compounds nor do they increase activation energy.

Final answer: A