What term describes a thin layer that separates or encloses cells or organelles?

What term describes a thin layer that separates or encloses cells or organelles?

• A. Cytoplasm
• B. Nucleus
• C. Membrane
• D. Chromosome

Answer: (C)

Membrane describes a thin boundary that separates or encloses. In cells, membranes form the plasma membrane that surrounds the entire cell and also enclose organelles such as mitochondria and the nucleus. They’re thin, flexible sheets made mainly of a lipid bilayer with embedded proteins, and they regulate what passes in and out to maintain different internal environments. The cytoplasm is the internal fluid inside the cell, not a boundary, so it doesn’t fit the idea of a separating layer. Chromosomes are DNA carries inside the nucleus, not boundaries. The nucleus itself is enclosed by a membrane, but the general term for that boundary is membrane, which is why it’s the best fit.