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

How is body heat primarily created?

1. From digestion

2. Through respiration

3. By muscle movement

4. Through environmental exposure

The correct answer is: Through respiration

Body heat is primarily generated through respiration, specifically during the process of cellular respiration. Cellular respiration is the biochemical process by which cells convert glucose and oxygen into energy. This process produces adenosine triphosphate (ATP), which is the energy currency of the cell, but it also releases heat as a byproduct. This heat plays a crucial role in maintaining the body's core temperature, especially in warm-blooded animals like humans. While digestion does contribute to the production of heat, as energy is released when food is metabolized, it is not the primary source of heat under normal circumstances. Muscle movement can also generate heat, particularly during physical activity, as muscles require energy (from respiration) to contract and function. However, without the ongoing process of respiration, muscle activity would not be sustainable. Environmental exposure does not directly create body heat; rather, it may influence how heat is retained or lost by the body. Thus, the process of respiration is integral to maintaining body heat, making it the primary mechanism for heat generation within the body.