Question 30

The head of a phospholipid is both hydrophilic and located on the outer side of the layer.

The head of a phospholipid is characterized by being hydrophilic, meaning it is attracted to water, and it is positioned on the outer side of the phospholipid bilayer, interacting with the aqueous environment.

A) It is hydrophilic.

This statement is correct as the head of a phospholipid contains a phosphate group, which makes it polar and thus attracted to water. This property is essential for the formation of biological membranes, allowing the heads to face outward toward the water in both the intracellular and extracellular environments.

B) It is hydrophobic.

This statement is incorrect. The head of a phospholipid is not hydrophobic; rather, it is the tail that is hydrophobic. The hydrophobic tails are repelled by water and face inward in the bilayer, away from the aqueous environments.

C) It is located on the outer side of the layer.

This statement is accurate as well. In a phospholipid bilayer, the hydrophilic heads are oriented toward the external environment and the cytoplasm, allowing them to interact with water, while the hydrophobic tails face each other in the interior.

D) Both A and C

This statement is correct because it combines the truths of options A and C. The head of a phospholipid is indeed hydrophilic and is located on the outer side of the bilayer, making this option the best representation of the properties of the phospholipid head.

Conclusion

Option D is the definitive correct answer because it accurately encapsulates the characteristics of the phospholipid head, stating that it is hydrophilic and located on the outer side of the layer. Options A and C, while correct on their own, do not provide as complete a description as D, which integrates both aspects. Options B fails to recognize the properties of the head, leading to its incorrectness.