Final answer:
Sulfur is essential for living organisms as it is involved in protein formation, present in vitamins and coenzymes, and plays a role in the sulfur cycle.
Step-by-step explanation:
Sulfur is an essential element for living organisms. It is involved in the formation of proteins through the amino acids cysteine and methionine. Sulfur is also present in vitamins and coenzymes that are important for various biological processes. It plays a role in the sulfur cycle, where it cycles between the oceans, land, and atmosphere through processes like decomposition, volcanic activity, and the burning of fossil fuels.