What is the primary composition of cells in the human body?

The correct answer highlights that cells in the human body are primarily composed of water, which accounts for about 80% of their total composition. Water is essential for various cellular functions, including acting as a solvent for biochemical reactions, regulating temperature, and maintaining cell structure and nutrient transport. The high water content is crucial for maintaining homeostasis and facilitating metabolic processes within the cells.

While proteins, fats, and carbohydrates play vital roles in cellular structure and function, their combined proportions are significantly lower than that of water. For instance, proteins are key components of cellular machinery and are involved in metabolic pathways, but they do not reach the high percentage that water does in cellular composition. Similarly, fats and carbohydrates contribute to cellular functions but are also substantially less than the quantity of water present in human cells. This emphasis on water underscores its fundamental role in sustaining life and biological processes in human cells.