HESI A2 Biology Practice Test 2026 – All-in-One Study Guide for Exam Success!

Prokaryotic cells are characterized by their lack of a membrane-bound nucleus. Instead, their genetic material, usually in the form of a single circular DNA molecule, is located in a region called the nucleoid, which is not encased by a membrane. This distinction is fundamental to the classification of prokaryotes, which include bacteria and archaea.

In contrast, prokaryotic cells do possess a cell membrane, which regulates the entry and exit of substances, as well as ribosomes, which are essential for protein synthesis. Additionally, they contain cytoplasm, which is the jelly-like substance that fills the cell, containing the necessary components for various metabolic processes. Thus, the absence of a nucleus is a defining feature of prokaryotic cells, making it the correct answer to the question.