Video Transcript
Which of the following is a primary function of the cell membrane? (A) To provide support and structure to the cell. (B) To synthesize, store, and transport proteins. (C) To separate the components of the cell from the surrounding medium or environment. Or (D) to prevent the entry and exit of substances into and out of the nucleus.
The cell membrane, also called the plasma membrane, is found in all cells. If we zoom in on the cell membrane, we can see that it’s made up of a phospholipid bilayer. This is semipermeable, meaning that only certain molecules can enter and exit. In this way, the cell membrane acts as a barrier that separates the inside of the cell from the outside of the cell.
Now let’s look at our different answer choices to choose the best one. Option (A) states “to provide support and structure to the cell.” While this is true, it’s not its primary function. So this is incorrect. Option (B) states “to synthesize, store, and transport proteins,” which is not true. Option (C) states “to separate the components of the cell from the surrounding medium or environment.” This is true and represents the primary function of the cell membrane. But let’s just check the last answer choice to be sure. Option (D) states “to prevent the entry and exit of substances into and out of the nucleus.” The nucleus is surrounded by a nuclear membrane, which is actually composed of two phospholipid bilayers. These in fact do prevent the entry and exit of substances into the nucleus. However, this question is asking about the cell membrane, so this is incorrect.
Therefore, the primary function of the cell membrane is answer choice (C), to separate the components of the cell from the surrounding medium or environment.
