A Level Biology Practice Exam

Eukaryotic cells are characterized by their complex structure, which includes a distinct nucleus that houses the cell's genetic material. This nucleus is surrounded by a nuclear membrane, distinguishing eukaryotic cells from prokaryotic cells, which lack a defined nucleus. In addition to the nucleus, eukaryotic cells also contain membrane-bound organelles, such as mitochondria, endoplasmic reticulum, and Golgi apparatus. These organelles carry out specialized functions within the cell, contributing to its overall efficiency and complexity.

Option A refers to cells without a nucleus, which describes prokaryotic cells, not eukaryotic. The third option suggests that eukaryotic cells only exist in multicellular organisms, but they are also found in unicellular organisms, such as yeast and protists. The final option incorrectly asserts that eukaryotic cells are exclusive to plants; in reality, eukaryotic cells are present in animals, fungi, and protists as well. Therefore, the defining feature of eukaryotic cells is indeed their nucleus and membrane-bound organelles.