In which of the following types of cells are gap junctions absent?

Correct answer: (c) Sperm cells

Explanation

A gap junction is a channel between two neighbouring cells through which ions and small molecules pass directly, so that the cells work together. They are found where cells must act as a unit, for example:

• in heart muscle, at the intercalated discs, so the heart contracts in step;
• between some nerve cells in the brain (electrical synapses);
• between an egg and the follicle cells around it.

A sperm cell is a free-swimming single cell, not joined to other cells, so it has no gap junctions.