Difficulty: Medium

Average Score: 72%

Which of the following statements is true regarding the structure of the cell membrane?

Rationale

The cell membrane consists of a phospholipid bilayer.

The fundamental structure of the cell membrane is a phospholipid bilayer, which forms the basic framework that encloses the cytoplasm of cells. This bilayer arrangement, with hydrophilic heads facing outward and hydrophobic tails facing inward, provides the membrane with fluidity and selective permeability, essential for maintaining the internal environment of the cell.

A (The cell membrane is composed of nucleic acids.) YOUR ANSWER

Nucleic acids, such as DNA and RNA, are not components of the cell membrane. They are primarily found within the cell's nucleus and cytoplasm, serving as genetic material and guiding protein synthesis. The cell membrane's structure relies on lipids and proteins, not nucleic acids.

B (The cell membrane is impermeable to all substances.) YOUR ANSWER

While the cell membrane provides a selective barrier, it is not impermeable to all substances. It allows the passage of certain molecules through diffusion, facilitated diffusion, and active transport. The phospholipid bilayer's selective permeability is crucial for nutrient uptake, waste removal, and communication with the cell's environment.

D (The cell membrane is made up of only proteins.) YOUR ANSWER

The cell membrane is composed of both lipids and proteins, with the phospholipid bilayer forming the primary structural framework. Proteins embedded within or associated with the bilayer perform various functions, such as transport, signaling, and structural support, but they do not solely constitute the membrane.

Conclusion

The cell membrane's structure is defined by its phospholipid bilayer, which provides a flexible yet stable barrier crucial for cellular integrity and function. This bilayer arrangement allows for selective permeability, enabling the cell to maintain homeostasis despite environmental changes. Incorrect options highlight misconceptions, as nucleic acids are absent from the membrane, complete impermeability is inaccurate, and proteins alone do not form the membrane's entirety. Understanding the membrane's composition is fundamental to grasping cellular function and interaction.

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