Why do growing cells require low metabolic entropy?

• A. Low entropy is produced spontaneously without energy.
• B. Growth requires assembling small molecules into highly organized cell structures.
• C. High entropy is necessary for macromolecule formation.
• D. Entropy must be high to drive synthesis.

Answer: (B)

Growing cells must build order. That means taking many small, simple molecules and linking them into highly organized, larger structures—proteins, nucleic acids, membranes, and complex molecular machines. Creating this level of organization reduces the cell’s internal entropy, so the cell must invest energy to drive those syntheses.

Energy from nutrient breakdown powers biosynthetic reactions and is released as heat or dispersed to the surroundings, which increases the overall entropy of the universe. So, while the cell locally decreases entropy by forming organized structures, it does so by coupling to energy input, keeping the second law satisfied.

Why the other ideas don’t fit: forming organized macromolecules isn’t spontaneous and without energy; it requires energy input to counter the natural tendency toward disorder. High entropy isn’t needed for making organized macromolecules, and saying entropy must be high to drive synthesis contradicts the need to reduce order during assembly.