Energy from respiration powers active processes, not passive ones

Steps:

• Respiration releases ATP energy for cellular work like synthesis and movement.
• Identify processes: diffusion is passive transport; others involve active cellular activities.
• Check each: diffusion needs no ATP; muscle contraction, enzyme production, and heat maintenance do.
• Conclude the one without energy use is diffusion.

Why A is correct:

• Diffusion down a concentration gradient is passive, driven by random molecular motion without ATP, per Fick's law of diffusion.

Why the others are wrong:

• B: Muscle contraction requires ATP hydrolysis for actin-myosin sliding.
• C: Protease production involves energy-intensive protein synthesis via ribosomes and ATP/GTP.
• D: Replacing body heat loss demands metabolic energy to maintain homeostasis.

Final answer: A