MTTC Secondary Integrated Science Practice Test 2025 – Complete Exam Prep

The primary function of the cell membrane is to act as a barrier between the inside of the cell and the external environment. This semi-permeable membrane controls the movement of substances in and out of the cell, maintaining homeostasis and allowing the cell to maintain a stable internal environment despite changes in the external environment. The cell membrane is composed primarily of a lipid bilayer with embedded proteins that facilitate communication and transport, serving not only as a protective barrier but also participating in various signaling pathways.

The other options represent different functions associated with cellular components. Protein synthesis occurs in the ribosomes, which are either free in the cytoplasm or attached to the endoplasmic reticulum. The storage of genetic information occurs in the nucleus, where DNA resides. Lastly, the modification and packaging of proteins take place in the endoplasmic reticulum and Golgi apparatus, which are also organelles within the cell, distinct from the function of the membrane. Understanding the specialized functions of cellular structures helps clarify the unique role of the cell membrane in overall cell function.