Final answer:
The nucleus is the most prominent organelle observed in cheek cells under a microscope, responsible for housing DNA and guiding protein synthesis.
Step-by-step explanation:
When viewing cheek cells under a microscope, the nucleus is the most prominent organelle that you are likely to observe. The nucleus houses the cell's DNA in the form of chromatin and is responsible for directing the synthesis of ribosomes and proteins. In most cheek cell preparations, called squamous epithelial cells, the nucleus should be visible with both low and high power objective lenses. When sketching these cheek cells, it is essential to include the cell membrane, cytoplasm, and the nucleus, which are easily observed. Additionally, adding bacterial cells can provide a scale of comparison, especially when keeping the size scale accurate between the cheek cell and bacterial cells.