Which of the following is true about cells?
A. In general, prokaryotic cells do not have a true nucleus or membrane-bound organelles, whereas eukaryotic cells contain both a nucleus and organelles enclosed by membranes.
B. Neither prokaryotic cells nor eukaryotic cells ever contain both a true nucleus that is well-defined and organelles that are separated from the cytoplasm by membranes.
C. Both eukaryotic cells and prokaryotic cells always contain both a true nucleus that is well-defined and organelles that are separated from the cytoplasm by membranes.
D. In general, eukaryotic cells do not have a true nucleus or membrane-bound organelles, whereas prokaryotic cells contain both a nucleus and organelles enclosed by membranes.
The correct answer and explanation is:
Correct Answer: A. In general, prokaryotic cells do not have a true nucleus or membrane-bound organelles, whereas eukaryotic cells contain both a nucleus and organelles enclosed by membranes.
Cells are the basic structural and functional units of life. They can be classified into two main categories: prokaryotic and eukaryotic. The key differences between them lie in their internal structures, particularly the presence or absence of membrane-bound components.
Prokaryotic cells, such as bacteria and archaea, are simpler in structure. They do not have a true nucleus. Instead, their genetic material, usually a single circular strand of DNA, floats freely in the cytoplasm within a region known as the nucleoid. Furthermore, prokaryotic cells do not possess membrane-bound organelles like mitochondria, endoplasmic reticulum, or Golgi apparatus. The lack of internal compartmentalization means all cellular functions occur in the same space without separation.
In contrast, eukaryotic cells, which are found in animals, plants, fungi, and protists, are more complex. They contain a true nucleus where the DNA is enclosed within a double membrane. This nucleus controls the cell’s activities and gene expression. Additionally, eukaryotic cells have numerous membrane-bound organelles, such as mitochondria for energy production, lysosomes for digestion, and endoplasmic reticulum for protein and lipid synthesis. These organelles allow compartmentalization of cellular processes, which increases efficiency and specialization.
The other answer choices are incorrect because they either claim that neither type of cell has a nucleus and organelles, or that both do, or they reverse the true characteristics of eukaryotic and prokaryotic cells. Only option A correctly distinguishes the two types based on well-established cellular biology principles.