Blood glucose concentration (Edexcel GCSE Biology): Revision Notes
📚 Revision Notes
Blood glucose concentration
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Glucose is essential for cells as it provides energy through respiration. It is important that the concentration of glucose in the blood is tightly regulated. This regulation is achieved primarily by the hormones insulin and glucagon, both produced by the pancreas.
How Insulin Controls Blood Glucose Concentration:
High Blood Glucose Levels:
- When blood glucose levels are too high (e.g., after eating a meal), the pancreas detects the rise and releases insulin into the bloodstream.
- Insulin allows glucose to move from the blood into cells where it can be used for respiration.
- In the liver and muscle cells, insulin triggers the conversion of excess glucose into glycogen for storage.
- As glucose moves out of the blood and is stored or used, the blood glucose level decreases back to normal.
How Glucagon Regulates Blood Glucose Concentration:
Low Blood Glucose Levels:
- When blood glucose levels are too low (e.g., during fasting or after physical activity), the pancreas releases a hormone called glucagon.
- Glucagon acts on the liver to convert stored glycogen back into glucose.
- The glucose is then released into the bloodstream, causing the blood glucose level to increase back to normal.
The Effects of Insulin and Glucagon:
| Low Glucose | High Glucose | |
|---|---|---|
| Effect on Pancreas | Insulin not secreted into the blood | Insulin secreted into the blood |
| Effect on Liver | Does not convert glucose into glycogen | Converts glucose into glycogen |
| Effect on Blood Glucose | Increases | Decreases |
| Too much glucose – Insulin (rises after meal) | Too little glucose• Glucagon(falls after exercise) |
|---|---|
| Eating carbs puts glucose in the blood from small intestine Respiration rate increases Glucose absorbed into cells Stimulates conversion of glucose into lipids (fats) | Stimulates liver cells to convert glycogen into glucose Respiration rate decreases Less glucose absorbed by cells Converts lipids & proteins into glucose |
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Summary:
- Insulin reduces blood glucose levels by promoting the uptake of glucose into cells and its conversion into glycogen for storage.
- Glucagon raises blood glucose levels by stimulating the breakdown of glycogen into glucose in the liver.
- Together, these two hormones maintain a balance in blood glucose concentration, ensuring that the body has a stable supply of energy
- The normal metabolism of cells removes glucose from the blood
- Vigorous exercise removes more glucose from blood
- Excess glucose can be stored at glycogen in liver & muscles
- When stores are full then excess glucose is stored as lipids (fat) in tissues