Question

which of the following options best describes why a phospholipid bilayer keeps water out of the cell? it dissolves easily in water. it has specific channels for water. it contains lipids which are hydrophobic.

Explanation:

• Analyze Option 1: Phospholipids have a hydrophobic (water - repelling) tail region. So they do not dissolve easily in water. This option is incorrect.
• Analyze Option 2: Specific channels for water (like aquaporins) are proteins, not part of the phospholipid bilayer's basic structure for excluding water. The phospholipid bilayer itself does not have these channels as a fundamental feature for keeping water out. This option is incorrect.
• Analyze Option 3: Phospholipids in the bilayer have hydrophobic fatty acid tails. Water is a polar molecule, and the hydrophobic tails repel water, creating a barrier that keeps water out of the cell (or controls its entry/exit). This option correctly explains the role of the phospholipid bilayer in keeping water out.

Answer:

C. It contains lipids which are hydrophobic. (Note: Assuming the third option is labeled C, if the original options had different labels, adjust the label accordingly. Based on the given options, the correct one is "It contains lipids which are hydrophobic.")