Sperm cell adaptations

A sperm cell is specialised to reach and fertilise an egg cell. Its structures help it swim to the egg, penetrate its outer layers and deliver genetic information.

Swimming towards the egg

The sperm’s tail beats to propel it through fluid towards the egg. The sperm contains many mitochondria, which carry out respiration and release energy to power the tail’s movement.

Entering the egg

At the head of the sperm is a cap called the acrosome. It contains enzymes that help digest through the outer layers of the egg, allowing the sperm nucleus to enter.

Delivering genetic information

The sperm’s nucleus is haploid: it contains one set of chromosomes, rather than the two sets usually found in body cells. The egg nucleus is also haploid. When the sperm and egg nuclei fuse, their chromosome sets combine, restoring the normal diploid number in the fertilised egg.