37. The cell membrane consists of a bilayer of phospholipids with proteins, cholesterol, and glycoproteins. This bilayer creates a hydrophobic region between two layers of lipids, making it which of the following?
Answer: C
The cell membrane is selectively permeable.
The cell membrane's structure, composed of a phospholipid bilayer, creates a hydrophobic region that allows it to control the passage of substances. This characteristic defines it as selectively permeable, meaning it regulates which molecules can enter or exit the cell.
A) Impermeable
This option suggests that the cell membrane does not allow any substances to pass through, which is incorrect. The bilayer does permit the movement of certain small molecules and ions, contradicting the definition of impermeability.
B) Permeable
While this option indicates that the membrane allows substances to pass through, it lacks the specificity of "selectively permeable." The cell membrane does not allow all substances to pass freely; rather, it selectively permits certain molecules, making this option too broad.
C) Selectively permeable
This option accurately describes the cell membrane's function. The structure of the bilayer, combined with the proteins and other components, allows it to control the passage of specific substances while restricting others, which is the essence of selective permeability.
D) Selectively impermeable
This option implies that the membrane is designed to prevent certain substances from passing through while allowing others, but it inaccurately suggests a level of impermeability that does not apply here. The cell membrane is not completely impermeable; instead, it selectively regulates permeability.
Conclusion
The correct answer, "selectively permeable," encapsulates the cell membrane's essential function of regulating substance movement. All other options fail to accurately represent the membrane’s ability to selectively allow certain molecules to cross while restricting others, which is vital for cellular function and homeostasis.