All questions of Eukaryotic Cells for MCAT Exam

Overview of the Endomembrane System
The endomembrane system is a complex network of membranes that play crucial roles in the synthesis, modification, transport, and degradation of biomolecules within eukaryotic cells.
Key Components
- Endoplasmic Reticulum (ER):
- There are two types: rough ER (with ribosomes) and smooth ER (without ribosomes).
- Rough ER is involved in protein synthesis and folding, while smooth ER is associated with lipid synthesis and detoxification.
- Golgi Apparatus:
- Acts as a processing and packaging center for proteins and lipids synthesized in the ER.
- Modifies, sorts, and sends these molecules to their destinations, which can include lysosomes, the cell membrane, or secretion outside the cell.
- Vesicles:
- Small membrane-bound sacs that transport materials between the different components of the endomembrane system.
- They carry proteins from the ER to the Golgi apparatus and from the Golgi to other destinations.
Why Other Options Are Incorrect
- Option A (Nucleus, mitochondria, and chloroplasts):
- The nucleus is part of the endomembrane system, but mitochondria and chloroplasts are not; they have their own membranes and functions.
- Option B (Ribosomes, Golgi apparatus, and lysosomes):
- Ribosomes are not membrane-bound organelles; they are involved in protein synthesis and can be free in the cytoplasm or attached to the rough ER.
- Option C (Cytoskeleton, peroxisomes, and vacuoles):
- The cytoskeleton provides structure but is not part of the endomembrane system. Peroxisomes are involved in metabolic processes and are not part of this system either.
Conclusion
Thus, the correct answer, option D, accurately reflects the essential components of the endomembrane system, highlighting their interconnected roles in cellular function.