OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the word equation for aerobic respiration?

1. Glucose + Oxygen → Carbon Dioxide + Water + Energy

2. Glucose + Oxygen → Lactic Acid + Energy

3. Carbon Dioxide + Water → Glucose + Oxygen

4. Glucose → Ethanol + Carbon Dioxide + Energy

The correct answer is: Glucose + Oxygen → Carbon Dioxide + Water + Energy

The word equation for aerobic respiration is accurately represented by "Glucose + Oxygen → Carbon Dioxide + Water + Energy." This equation summarizes the process by which cells generate energy through the reaction of glucose and oxygen. In aerobic respiration, glucose, a simple sugar and key energy source, undergoes breakdown within cells in the presence of oxygen. The products of this reaction are carbon dioxide and water, which are expelled as waste products, while energy is released, typically in the form of adenosine triphosphate (ATP), which cells use for various functions, such as muscle contraction, nerve impulse propagation, and biosynthesis. Understanding this equation is fundamental in biology as it highlights the importance of oxygen in energy production and the efficient use of glucose in cellular metabolism. This process is crucial for most living organisms, including humans, as it provides the energy necessary for survival and functioning. In contrast, the other options provided refer to different processes. For instance, the reaction involving lactic acid pertains to anaerobic respiration, which occurs when oxygen is scarce, while the equations involving carbon dioxide and ethanol pertain to fermentation processes, which also happen in the absence of sufficient oxygen. Thus, the chosen word equation emphasizes the critical role of aerobic respiration in energy production