GCSE Biology - Regulating Glucose | Glucose & Glycogen & Glucagon | Blood Glucose Graphs

Blood Glucose Regulation

The hormones insulin and glucagon keep blood glucose concentration within a suitable range. Cells need glucose for respiration, but too much glucose in the blood can damage tissues.

When Blood Glucose Is Too High

• After a carbohydrate-rich meal, carbohydrates are digested into glucose.
• Glucose is absorbed into the bloodstream, causing blood glucose concentration to rise.
• The pancreas detects the increase and releases insulin.
• Insulin binds to receptors on cells, prompting them to take up glucose from the blood.
• Liver and muscle cells take up much of the excess glucose and join glucose molecules together to make glycogen, a storage form of glucose.
• As glucose is removed from the blood, blood glucose concentration falls towards its usual level.

When Blood Glucose Is Too Low

• If blood glucose falls too far—for example, after skipping a meal—the pancreas detects the decrease and releases glucagon.
• Glucagon acts mainly on liver cells.
• These cells break down stored glycogen into glucose and release the glucose into the bloodstream.
• Blood glucose concentration rises towards its usual level, supplying cells with glucose for respiration.

Negative Feedback and Graphs

Insulin and glucagon have opposing effects, together forming a negative feedback loop:

• High glucose → insulin released → glucose falls.
• Low glucose → glucagon released → glucose rises.

On a blood glucose graph, glucose may rise after a meal and then fall as insulin acts. It can also fall below the usual level and rise again after glucagon acts. The level fluctuates around the appropriate range rather than remaining perfectly constant, as the body continually adjusts it.

Key distinction: Glucagon is a hormone; glycogen is a molecule made from many glucose molecules and used for storage.

Speakers and Sources

• Cognito narrator/presenter — explains blood glucose regulation.
• Cognito.org — mentioned in the outro as a resource for videos and study materials.