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The levels of glucose, insulin and glucagon were measured in the plasma of 24 healthy adults at intervals over a 5-hour period - HSC - SSCE Biology - Question 31 - 2020 - Paper 1
Question 31
The levels of glucose, insulin and glucagon were measured in the plasma of 24 healthy adults at intervals over a 5-hour period. After 1 hour at rest the patients ate... show full transcript
Worked Solution & Example Answer:The levels of glucose, insulin and glucagon were measured in the plasma of 24 healthy adults at intervals over a 5-hour period - HSC - SSCE Biology - Question 31 - 2020 - Paper 1
Step 1
Explain all the graphs with respect to the negative feedback control of blood glucose in healthy humans.
Answer
The plasma glucose levels in the first 60 minutes represent resting levels. After the meal, the plasma glucose rises due to absorption of glucose from food into the bloodstream.
Rising blood glucose stimulates β cells in the pancreas to release insulin, which prompts body cells to absorb glucose to be utilized in metabolism, and to store excess glucose as glycogen. This increase in plasma glucose is depicted in Figure 1, which shows an upward trend after the meal.
As the cells utilize glucose, plasma glucose levels then decrease, demonstrating the negative feedback mechanism. Consequently, insulin levels also drop, evident in Figure 2, where insulin levels fall after an initial spike.
Glucagon, as shown in Figure 3, is another critical hormone in this feedback loop. It is released when blood glucose levels drop, signaling the liver to convert stored glycogen back into glucose. This helps maintain blood glucose levels, preventing them from falling too low after the initial insulin response.