Final answer:
The most abundant molecules in prokaryotic or eukaryotic cells are proteins, due to their extensive roles in cellular functions. Myelin is primarily composed of lipids and proteins. Both prokaryotic and eukaryotic cells contain ribosomes, nucleic acids, the plasma membrane, and the cytoplasm as common structures.
Step-by-step explanation:
The type of molecule that would be most abundant in a typical prokaryotic or eukaryotic cell is proteins. Proteins perform a variety of functions essential to the cell, they act as enzymes, structural components, signaling molecules, and partake in cell transport and movement. While carbohydrates, lipids, and nucleic acids are also vital components of cells, proteins are central to most cellular processes and are required in larger quantities for the structure and regulation of the body's tissues and organs.
Regarding the main components of myelin, which is the insulating layer around nerve cells, the two macromolecules primarily involved are lipids and proteins. Myelin's composition is critical because it enhances the speed and efficiency of electrical signals in neurons.
When considering commonalities between prokaryotic and eukaryotic cells, all cells indeed contain ribosomes, nucleic acids, the plasma membrane, and the cytoplasm. These are fundamental structures necessary for the survival of the cell, allowing it to synthesize proteins, contain genetic information, separate internal contents from the external environment, and maintain the necessary biochemical reactions.