Question 17

The plasma membrane is arranged in a double layer of phospholipids.

The plasma membrane consists of a double layer of phospholipids, which creates a flexible barrier around cells and is essential for maintaining their integrity and functionality.

A) In a single layer made of proteins

This option is incorrect because the plasma membrane is not composed solely of proteins, nor is it structured as a single layer. Instead, the membrane primarily consists of a lipid bilayer, which provides the necessary structural characteristics for cell function.

B) In a double layer made of proteins

This option is also incorrect. While proteins are present in the membrane, they do not form the double layer; instead, the plasma membrane is primarily made of a double layer of phospholipids, with proteins embedded within or associated with this bilayer.

C) In a single layer of phospholipids

This option is incorrect because the plasma membrane is not formed by a single layer of phospholipids. A single layer would not provide the necessary structural integrity or functionality required for cellular processes.

D) In a double layer of phospholipids

This option is correct. The plasma membrane is indeed arranged in a double layer of phospholipids, which allows for the formation of a semi-permeable barrier that regulates the movement of substances in and out of the cell.

Conclusion

The correct answer is D, as the plasma membrane's double layer of phospholipids is fundamental to its role in cell structure and function. Options A, B, and C fail to accurately describe the arrangement and composition of the plasma membrane, highlighting the importance of understanding membrane biology in cellular processes.