Which cellular structures can be seen under a light microscope?

• A. Mitochondria only
• B. Ribosomes only
• C. Cell membrane, cytoplasm, nucleus, nucleolus, lysosomes
• D. Endoplasmic Reticulum only

Answer: (C)

Light microscopy can reveal structures that are large enough and suitably contrasted to be distinguished at about 0.2 micrometers or larger. In a typical cell, the cell membrane forms a visible boundary, and the cytoplasm is the recognizable interior region. The nucleus is large enough to appear as a distinct mass, and within it you can often see the nucleolus as a dense spot. Lysosomes can also be seen as small vesicles when stained appropriately. On the other hand, mitochondria and ribosomes are generally too small to resolve as separate structures with standard light microscopy, and the endoplasmic reticulum does not usually appear as a distinct network under this technique. So the structures you can see with light microscopy include the cell membrane, cytoplasm, nucleus, nucleolus, and lysosomes.