Question

Carbohydrates present on the plasma membrane

• A. has structural role
• B. forms channel
• C. act as carrier
• D. helps in molecular recognition

Hint:

Carbohydrates on the outer plasma membrane function as the cell's "antennae" or "ID tags." They are essential for molecular and cell-to-cell recognition, allowing the immune system and other cells to identify them.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The plasma membrane is composed of a phospholipid bilayer containing proteins and carbohydrates.
The carbohydrates are located exclusively on the extracellular surface of the membrane, covalently bound to lipids (glycolipids) or proteins (glycoproteins).

Step 2: Detailed Explanation:
Let us analyze the functional roles of the components of the plasma membrane:
Structural Role (A): Primarily performed by the phospholipid bilayer and cytoskeletal proteins.
Channels (B) and Carriers (C): Formed by transmembrane proteins that transport ions and molecules across the membrane.
Molecular Recognition (D): This is the primary function of the extracellular carbohydrates.
These oligosaccharide chains form a protective sugar coat called the glycocalyx.
Because of their diverse structures, these sugar chains act as unique molecular identification tags.
They play a vital role in cell-to-cell communication, cell adhesion, immune responses (enabling cells to distinguish "self" from "non-self"), and serving as receptor binding sites for hormones, nutrients, and pathogens.
Therefore, membrane carbohydrates are primarily involved in molecular and cell-to-cell recognition.

Step 3: Final Answer:
Carbohydrates on the plasma membrane are primarily involved in molecular recognition, corresponding to option (D).