Cell biology fundamentals: identify the structure that is absent from eukaryotic cells In general microbiology, which one of the following cellular structures is NOT found in eukaryotic cells such as those of animals, plants, fungi, or protists?

Introduction / Context:
Eukaryotic cells are characterized by membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, and the Golgi apparatus. Some eukaryotes (plants and many protists) also contain chloroplasts. By contrast, structures historically described in certain prokaryotes may not occur in eukaryotes at all. This question asks you to identify the structure absent from eukaryotic cells.

Given Data / Assumptions:

• Eukaryotes can contain mitochondria and a Golgi apparatus; plants and some protists contain chloroplasts.
• Prokaryotes lack membrane-bound organelles such as mitochondria and Golgi bodies.
• Mesosome is a structure reported in older electron micrographs of bacteria.

Concept / Approach:

The key is to recall canonical eukaryotic organelles and to distinguish them from structures attributed to bacteria. The mesosome, once thought to be an invagination of the bacterial plasma membrane with respiratory roles, is now understood largely as a fixation artifact in electron microscopy and, in any case, is a prokaryotic finding rather than a eukaryotic organelle. Therefore, when asked what is absent from eukaryotes, mesosome is the correct choice.

Step-by-Step Solution:

Verification / Alternative check:

Eukaryotic cell diagrams across textbooks consistently include mitochondria and Golgi bodies; mesosomes are never depicted in eukaryotes and are discussed, if at all, in the context of bacterial ultrastructure controversies.

Why Other Options Are Wrong:

• Mitochondria: Present in virtually all aerobic eukaryotes and many anaerobes as derivatives.
• Chloroplasts: Present in plants and many algae; absent from animals but still a bona fide eukaryotic organelle.
• Golgi apparatus: Core component of eukaryotic endomembrane trafficking.
• Centrioles: Present in many animal cells and some protists; even if absent in plants, they are eukaryotic structures, not prokaryotic.

Common Pitfalls:

• Assuming that if plants lack centrioles widely, then centrioles are 'noneukaryotic'; the question asks what eukaryotes as a whole lack, which is mesosome.
• Believing mesosomes are universal bacterial functional organelles; they are now considered artifacts.

Final Answer:

Mesosome