Question

1. which of the following statements explains why the phospholipid molecules of the plasma n are arranged with the heads facing outward, toward the cytosol and extracellular fluid, and the facing inward, toward each other? a. this arrangement creates a fully permeable barrier that allows various materials to pass in or out of the cell. b. this arrangement blocks all materials from passing in or out of the cell. c. the heads are hydrophobic and the tails are hydrophilic. d. the heads are hydrophilic and the tails are hydrophobic.

Explanation:

To solve this, we analyze each option:

• Option a: Plasma membrane is selectively permeable, not fully permeable. Eliminate.
• Option b: It allows some materials to pass, not block all. Eliminate.
• Option c: Phospholipid heads are hydrophilic (water - attracting), tails are hydrophobic (water - repelling). This option has them reversed. Eliminate.
• Option d: Phospholipid heads are hydrophilic (so face aqueous environments like cytosol and extracellular fluid), tails are hydrophobic (so face each other, away from water). This explains the arrangement.

Answer:

d. The heads are hydrophilic and the tails are hydrophobic.