A Level Biology Practice Exam

Which structure is described as a network of fibers in the cytoplasm of eukaryotic cells?

1. Cell membrane

2. Cytoplasm

3. Cytoskeleton

4. Ribosomes

The correct answer is: Cytoskeleton

The cytoskeleton is indeed described as a network of fibers found in the cytoplasm of eukaryotic cells. This structure plays an essential role in maintaining the cell's shape, providing mechanical support, and facilitating movement both within the cell and of the cell itself. It consists of three primary components: microfilaments, intermediate filaments, and microtubules, each contributing to various cellular functions. Microfilaments are involved in movement and shape changes, intermediate filaments provide structural stability, and microtubules are key in intracellular transport and cell division. The cytoskeleton also serves as tracks for the movement of organelles and vesicles within the cell, indicating its critical function in cellular organization and transport processes. The other options do not accurately reflect the described structure. The cell membrane is primarily a lipid bilayer that encloses the cell, the cytoplasm refers to the entire contents within the cell (excluding the nucleus), and ribosomes are organelles responsible for protein synthesis but do not form a network of fibers. Thus, the cytoskeleton is unique in its fibrous network composition and multifunctional roles within eukaryotic cells.