Question

which of the following statements best explains why phospholipids create a bilayer when placed in a water-based environment?
○ the fatty acid tails have opposite charges from one another so they create hydrogen bonds and create a bilayer.
○ the shape of the molecule causes them to arrange in a double layer.
○ there is no reason, the molecules just happen to arrange themselves like this.
○ the fatty acid tails are hydrophobic and need to hide from water, so they create a bilayer where the middle has no water.

Explanation:

1. Analyze the first option: Fatty acid tails are non - polar and do not have opposite charges to form hydrogen bonds in this context. So this option is incorrect.
2. Analyze the second option: The shape of the molecule is not the main reason for bilayer formation. The key is the hydrophobic and hydrophilic regions. So this option is incorrect.
3. Analyze the third option: There is a scientific reason (related to hydrophobic and hydrophilic interactions) for the bilayer formation, so this option is incorrect.
4. Analyze the fourth option: Phospholipids have a hydrophilic head and hydrophobic fatty acid tails. In a water - based environment, the hydrophilic heads interact with water, and the hydrophobic tails (which repel water) cluster together, leading to the formation of a bilayer where the tails are in the middle (away from water) and the heads are on the outside (interacting with water). This option correctly explains the bilayer formation.

Answer:

The fatty acid tails are hydrophobic and need to hide from water, so they create a bilayer where the middle has no water.