Question

unit 1.4 cell transport, homeostasis, feedback quiz 2025
after eating a large piece of cake, a student’s blood glucose concentration rises from 90 mg/dl to 160 mg/dl. since this is an imbalance, the pancreas detects the increase and releases insulin, which signals body cells to take in glucose and the liver to store glucose as glycogen. this results in blood glucose concentration lowering back down to 90 mg/dl.
which feedback mechanism is this an example of?
○ no feedback loop, because glucose naturally moves into cells by simple diffusion.
○ positive feedback, because insulin release increases the production of more insulin.
○ negative feedback, because insulin lowers blood glucose levels back toward normal.
○ positive feedback, because glucose levels keep rising until they level off naturally.

Explanation:

1. Analyze each option:

• Option 1: Glucose entering cells here is due to insulin - mediated uptake, not simple diffusion, and there is a feedback loop (insulin response to glucose change), so this is wrong.
• Option 2: Positive feedback amplifies a change, but insulin works to reverse the glucose increase, not increase insulin production in a positive - feedback - like way. So this is wrong.
• Option 3: Negative feedback is a mechanism that reverses a deviation from a set point. Here, blood glucose rises (deviation from normal ~90 mg/dL), pancreas releases insulin, and insulin acts to lower glucose back to normal. This fits negative feedback.
• Option 4: Glucose levels do not keep rising; insulin acts to lower them, and this is not positive feedback (positive feedback would amplify the rise). So this is wrong.

Answer:

Negative feedback, because insulin lowers blood glucose levels back toward normal.