OCR GCSE Biology Practice Exam 2025 – Comprehensive All-in-One Guide to Exam Success

Eukaryotic cells are characterized by the presence of a nucleus, which is a distinct membrane-bound organelle that houses the cell's genetic material (DNA). This is a fundamental difference from prokaryotic cells, which do not have a nucleus; their DNA is located in a region called the nucleoid that is not enclosed by a membrane. The presence of a nucleus in eukaryotic cells enables more complex regulation of gene expression and allows for multiple linear chromosomes compared to the single circular chromosome often found in prokaryotic cells.

In addition to containing a nucleus, eukaryotic cells also possess other membrane-bound organelles such as mitochondria and the endoplasmic reticulum, allowing for compartmentalization of cellular processes, which contributes to their complexity. This structural organization facilitates specialized functions that are essential for the survival and efficiency of eukaryotic organisms, distinguishing them significantly from prokaryotic cells.