Which statement about the cell membrane is true?
A)It contains cellulose and sugars that are involved in communication.
B)It is present in animal cells only.
C)It is rigid and elastic for supporting the cell’s shape.
D)It prevents harmful substances from entering a cell.
The Correct Answer and Explanation is :
The correct answer is D) It prevents harmful substances from entering a cell.
Explanation:
The cell membrane, also known as the plasma membrane, is a crucial structure in both prokaryotic and eukaryotic cells. It is primarily composed of a phospholipid bilayer, which serves as a barrier between the interior of the cell and its external environment. This bilayer consists of hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails, allowing the membrane to be selectively permeable.
One of the primary functions of the cell membrane is to control the movement of substances in and out of the cell. It prevents harmful substances, such as toxins and pathogens, from entering the cell while allowing essential nutrients and waste products to pass through. This selective permeability is vital for maintaining homeostasis, which is the stable internal environment necessary for the cell’s functioning.
In addition to its protective role, the cell membrane also plays a significant part in cell signaling and communication. Embedded proteins act as receptors, allowing the cell to respond to external signals such as hormones or neurotransmitters. Furthermore, the membrane contains carbohydrates that can facilitate cell recognition and interaction, which is essential for immune response and tissue formation.
It is important to note that the statement A) is incorrect because the cell membrane does not contain cellulose (a component of plant cell walls); instead, it contains proteins and carbohydrates for communication. Statement B) is false, as cell membranes are present in all cell types, including both plant and animal cells. Finally, C) is misleading; while the membrane is flexible and can change shape, it is not rigid like some other cellular structures (e.g., the cell wall in plants).
In summary, the cell membrane’s primary function of preventing harmful substances from entering the cell (option D) highlights its critical role in protecting cellular integrity and ensuring proper function.