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

How are blood glucose levels maintained in the body?

1. Through emotional regulation

2. By increasing fluid intake

3. Through homeostasis

4. By reducing physical activity

The correct answer is: Through homeostasis

Blood glucose levels are maintained through the process of homeostasis, which is the body's ability to regulate its internal environment to maintain a stable, constant condition despite changes in external factors. In the context of blood glucose levels, homeostasis involves a complex interplay of hormones, primarily insulin and glucagon, produced by the pancreas. When blood glucose levels rise after consuming food, insulin is released to facilitate the uptake of glucose by cells, thereby lowering blood sugar levels. Conversely, when blood glucose levels drop, glucagon is released, prompting the liver to convert stored glycogen back into glucose and release it into the bloodstream. This balancing act ensures that the body has a consistent supply of energy while preventing the potentially harmful effects of too high or too low glucose levels. The other options do not directly relate to the physiological mechanisms that regulate blood glucose. Emotional regulation and physical activity can influence glucose levels but are not the primary mechanisms for maintaining homeostasis. Increasing fluid intake does not specifically address blood glucose control but is important for overall hydration. Thus, homeostasis is the central concept that explains how blood glucose levels are kept within a narrow range.