Which of the following forms of living cells is characterized by having a defined nucleus and membrane-bound organelles?
Prokaryotic cells
Eukaryotic cells
Archaea
Bacterial cells
Correct Answer:B
Explanation
The correct option is B. Eukaryotic cells.
Detailed Explanation:
Definition of Eukaryotic Cells:
Eukaryotic cells are characterized by the presence of a defined nucleus, which is a membrane-bound structure that contains the cell's genetic material (DNA). In addition to the nucleus, eukaryotic cells also have various membrane-bound organelles, such as mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes, which perform specific functions within the cell.
Comparison with Prokaryotic Cells:
Prokaryotic cells, which include bacteria and archaea, do not have a defined nucleus. Instead, their genetic material is located in a region called the nucleoid, which is not membrane-bound. Prokaryotic cells are generally simpler and smaller than eukaryotic cells and lack the complex organelles found in eukaryotes.
Characteristics of Eukaryotic Cells:
Nucleus: The defining feature of eukaryotic cells is the nucleus, which protects the DNA and allows for more complex regulation of gene expression.
Membrane-bound Organelles: Eukaryotic cells have organelles that are enclosed by membranes, allowing for compartmentalization of different cellular processes. This organization is crucial for the efficiency and specialization of cellular functions.
Size: Eukaryotic cells are typically larger than prokaryotic cells, often ranging from 10 to 100 micrometers in diameter.
Why Other Options Are Incorrect:
A. Prokaryotic cells: As mentioned, prokaryotic cells lack a defined nucleus and membrane-bound organelles. They are simpler in structure and include organisms like bacteria and archaea.
C. Archaea: Archaea are a type of prokaryotic cell. They share similarities with bacteria but are distinct in their genetic and biochemical properties. Like bacteria, they do not have a defined nucleus or membrane-bound organelles.
D. Bacterial cells: Bacterial cells are also prokaryotic and, like archaea, do not possess a defined nucleus or membrane-bound organelles. They are characterized by their simpler structure compared to eukaryotic cells.
Summary of Key Points:
Eukaryotic cells have a defined nucleus and membrane-bound organelles, allowing for complex cellular functions.
Prokaryotic cells (including bacteria and archaea) lack a nucleus and membrane-bound organelles, making them simpler in structure.
The presence of organelles in eukaryotic cells enables compartmentalization, which enhances cellular efficiency and specialization.
Revision Summary:
Eukaryotic cells: Defined nucleus and membrane-bound organelles.
Prokaryotic cells: No defined nucleus; simpler structure.
Archaea and bacteria are both prokaryotic and lack membrane-bound organelles.
Eukaryotic cells are generally larger and more complex than prokaryotic cells.