Final answer:
A mutation in the b subunit of the insulin receptor that destroys enzymatic activity will prevent a cell from responding as expected to increased blood glucose levels. Additional insulin molecules will not overcome this mutation because the mutated receptor cannot transmit the signal for glucose uptake.
Step-by-step explanation:
A mutation in the b subunit of the insulin receptor that destroys the enzymatic activity of this subunit will prevent the cell from responding as expected when blood glucose levels increase. This is because the enzymatic activity of the b subunit is necessary for the insulin receptor to signal glucose uptake. Without this activity, the glucose channels will not open, leading to the accumulation of glucose in the blood.
The release of additional insulin molecules will not be able to overcome this mutation because the mutated receptor is unable to transmit the signal for glucose uptake. Even with more insulin molecules present, the response will still be impaired due to the lack of enzymatic activity in the mutated receptor.