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

What is the function of glucagon in the body?

1. A hormone that enables fat storage

2. A hormone that converts glucose to glycogen

3. A hormone that tells the liver to convert glycogen back into glucose

4. A hormone that promotes insulin secretion

The correct answer is: A hormone that tells the liver to convert glycogen back into glucose

Glucagon plays a crucial role in blood sugar regulation by primarily acting on liver cells to convert glycogen, which is a stored form of glucose, back into glucose. When blood sugar levels drop, glucagon is released from the pancreas to prompt the liver to break down glycogen and release glucose into the bloodstream. This process helps to raise blood sugar levels, ensuring that the body has a constant supply of energy, especially between meals or during periods of increased energy demand. Understanding this concept is fundamental as it highlights the opposing roles of glucagon and insulin; while glucagon raises blood sugar levels, insulin lowers them by promoting the uptake of glucose into cells and the storage of glucose as glycogen.