# DBT JRF 2022 — Question 33

Exam: DBT JRF 2022 · Section: A · Topic: Cell Biology › Cell Junctions & Intercellular Communication · Difficulty: Medium

## Question

Gap junctions are absent in:

## Options

- **A.** Brain cells.
- **B.** Cardiac muscle cells.
- **C.** Liver cells.
- **D.** Erythrocytes.

## Answer

Option D

## Explanation

Gap junctions and cell communication: Gap junctions are intercellular channels made of connexin proteins that allow direct cytoplasmic communication between adjacent cells, passing ions and small molecules up to ~1 kDa. Present in: • Brain cells (neurons and especially glia) • Cardiac muscle cells (essential for synchronised contraction via electrical coupling) • Hepatocytes (liver cells) Absent in: • Erythrocytes (red blood cells): They are enucleated, lack most organelles, and are terminally differentiated with no nucleus. They have no need for direct cell-to-cell communication and do NOT express connexins. Answer: Erythrocytes (Option 4).

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