Final answer:
Cells produce energy most efficiently through aerobic metabolism, which occurs in mitochondria in eukaryotic cells or the plasma membrane in prokaryotic cells.
Step-by-step explanation:
The most efficient way for cells to produce energy is through aerobic metabolism. This process occurs in mitochondria in eukaryotic cells or the plasma membrane in prokaryotic cells. Aerobic metabolism, also known as cellular respiration, utilizes oxygen to generate ATP through a process called oxidative phosphorylation. This process provides the majority of ATP needed for cellular functions.