Question

when blood sugar rises after a meal, cells must take in glucose to keep balance. which role of the cell membrane is most important here? it sends glucose to the nucleus to make dna; it breaks down glucose into energy; it decides which materials like glucose can enter the cell; it blocks glucose when there is too much; rewatch

Explanation:

1. Analyze Option 1: The cell membrane does not send glucose to the nucleus for DNA synthesis. DNA synthesis uses nucleotides, not glucose, and the nucleus is not the destination for glucose uptake related to energy or balance. So this option is incorrect.
2. Analyze Option 2: Breaking down glucose into energy is the function of cellular respiration, mainly occurring in the mitochondria, not the cell membrane. So this option is incorrect.
3. Analyze Option 3: The cell membrane is selectively permeable, meaning it regulates which substances (like glucose) can enter or exit the cell. When blood sugar rises, the cell membrane allows glucose to enter the cell to maintain balance, which matches the description of its selective permeability role. This option is correct.
4. Analyze Option 4: The cell membrane does not simply "block" glucose when there is too much in a regulatory sense for blood sugar balance. It regulates uptake based on the cell's needs and the body's hormonal signals (like insulin), not a simple blocking mechanism. So this option is incorrect.

Answer:

It decides which materials like glucose can enter the cell (the third option).