What molecule is formed as a byproduct of cellular respiration?

• A. Glucose
• B. Oxygen
• C. Carbon dioxide
• D. Water

Answer: (C)

During cellular respiration, glucose is broken down to produce energy in the form of adenosine triphosphate (ATP). This process occurs in several stages: glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (electron transport chain and chemiosmosis).

As a result of these metabolic processes, carbon dioxide is produced as a waste product. Specifically, during the citric acid cycle, CO2 is released when carbon atoms from the glucose molecule are metabolized. This carbon dioxide is then expelled from the cell and ultimately from the organism, as it is a byproduct of aerobic respiration.

While water is also a byproduct of cellular respiration, it is formed later in the electron transport chain when electrons combine with oxygen and protons, thus both water and carbon dioxide are byproducts. However, carbon dioxide is more commonly recognized as a primary waste product resulting directly from the metabolism of organic molecules like glucose. Therefore, it’s accurate to state that carbon dioxide is the main molecule formed as a byproduct of cellular respiration.