Enzymes facilitate reactions by lowering activation energy

Steps:

• Identify statement 1: Enzymes act as catalysts by binding substrates in the active site, positioning reactive groups closely for efficient reaction.
• Evaluate statement 2: Enzymes reduce activation energy (Ea), allowing more substrate molecules to possess sufficient kinetic energy to overcome the lowered Ea barrier compared to uncatalyzed reactions.
• Assess statement 3: By decreasing Ea, enzymes enable reactions at body temperature (around 37°C), far lower than the high temperatures required without enzymes.
• Conclude all statements accurately describe enzyme action, selecting option A.

Why A is correct:

• Enzymes lower Ea per transition state theory, increasing reaction rate by orienting substrates (1), providing more molecules with sufficient energy (2), and allowing physiological temperatures (3).

Why the others are wrong:

• B omits valid effects on energy and temperature.
• C excludes the energy distribution benefit in statement 2.
• D ignores substrate positioning in statement 1.

Final answer: A