Which of the following best describes prokaryotes?

Prokaryotes are best described as single-celled organisms without membrane-bound organelles. This classification is essential as it highlights two primary characteristics of prokaryotic cells. Firstly, they are typically unicellular, meaning they consist of a single cell which carries out all necessary functions for life, contrasting with multicellular organisms which have specialized cells.

Secondly, prokaryotes lack membrane-bound organelles, such as a nucleus, mitochondria, or endoplasmic reticulum, which are characteristic of eukaryotic cells. Instead, their genetic material is usually organized in a single circular DNA molecule that is found in a region of the cell called the nucleoid. This simplicity in structure is a defining feature of prokaryotes, making them distinct from more complex eukaryotic organisms.

In the context of the other options, multicellular, complex organisms refer to eukaryotes, while cells with a defined nucleus are characteristic of eukaryotic cells as well. Lastly, the statement about prokaryotes being larger than eukaryotes is inaccurate; in fact, prokaryotic cells are generally smaller than eukaryotic cells. Therefore, the emphasis on being single-celled and the absence of membrane