What is the primary purpose of respiration in living organisms?

The primary purpose of respiration in living organisms is to convert glucose and oxygen into energy. This process is crucial because living organisms require energy to perform vital functions such as growth, maintenance, and reproduction. During cellular respiration, glucose is broken down in the presence of oxygen, resulting in the production of energy in the form of adenosine triphosphate (ATP), along with by-products like carbon dioxide and water.

This energy production is central to all metabolic processes, allowing organisms to harness the chemical energy stored in food. While other options mention important biological processes, they do not capture the primary role of respiration, which is fundamentally about energy conversion. For instance, producing glucose is a function of photosynthesis, which occurs in plants, and expelling carbon dioxide is a by-product of respiration rather than its primary purpose. Similarly, absorbing nutrients relates to digestion and nutrient uptake rather than respiration. Thus, the focus on energy production underscores the essential role of respiration in sustaining life.