What functions do carbohydrates serve in the cell membrane?

• A. Structural components of the nucleus
• B. Lubricants, adhesives, receptors, and self-recognition
• C. Primary energy source
• D. Genetic information carriers

Answer: (B)

Carbohydrate chains on the cell surface, attached to lipids and proteins, form the glycocalyx a sugary coating that extends into the extracellular space. This coating serves several roles: it acts as a lubricant to reduce friction when cells move or come into contact, it helps cells stick to each other and to the extracellular matrix (adhesion), and it participates in signaling and recognition processes because the carbohydrate moieties can interact with specific molecules and receptors. These surface carbohydrates also provide self-recognition cues, helping the immune system distinguish the body's own cells from foreign invaders.

They aren’t the cell’s main energy source, which comes from metabolizing glucose and other carbohydrates inside the cytoplasm and mitochondria. They also don’t carry genetic information—that role belongs to DNA and RNA. The membrane carbohydrates’ main job is organizing, signaling, and identifying the cell surface.