MCAT Content / Classification And Structure Of Prokaryotic Cells / Lack Of Nuclear Membrane And Mitotic Apparatus

Lack of nuclear membrane and mitotic apparatus

Topic: Classification And Structure Of Prokaryotic Cells

Prokaryotic cells lack a nuclear membrane, and mitotic apparatus such as spindles, and asters.

Prokaryote cells lack a nucleus surrounded by a complex nuclear membrane and generally have a single, circular chromosome located in a nucleoid. Their genetic material is located in the nucleoid rather than a membrane-bound nucleus. They lack membrane-bound organelles. However, they often contain inclusions that compartmentalize their cytoplasm. Bacteria do not have spindles and asters that make up the eukaryotic mitotic apparatus. Instead, the prokaryotic cytoskeleton helps pull the replicated DNA apart during division.


Practice Questions


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MCAT Official Prep (AAMC)

Practice Exam 1 B/B Section Question 45

Key Points

• Prokaryotic cells differ from eukaryotic cells in that their genetic material is contained in a nucleoid rather than a membrane-bound nucleus. Also, prokaryotic cells generally lack membrane-bound organelles.

• Bacteria do not have spindles and asters that make up the eukaryotic mitotic apparatus.


Key Terms

nucleoid:  an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material

prokaryote: an organism whose cell (or cells) are characterized by the absence of a nucleus or any other membrane-bound organelles

nuclear membrane: a double membrane that encloses the cell nucleus

nucleus: a membrane-bound organelle that contains genetic material

spindle: forms near the cell nucleus during mitosis or meiosis to draw the chromosomes to opposite poles of the cell.

aster: an array of microtubules associated with a centrosome in a dividing cell



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