Which option represents a described function of proteins?

• A. Transport: Hemoglobin
• B. Energy storage: Glucose
• C. Hormones: Insulin
• D. Nucleic acid synthesis

Answer: (A)

Proteins carry out specific tasks in the cell, and one classic function is transport. Hemoglobin is a protein in red blood cells that binds oxygen in the lungs and delivers it to tissues throughout the body. Its ability to reversibly bind oxygen, thanks to its structure and heme groups, is a textbook example of how a protein directly performs a transport role.

Energy storage described with glucose points to a carbohydrate, not a protein. Nucleic acid synthesis can involve enzymes, which are proteins, but the option lists the product/process rather than a direct, timeless function of a protein. Hormones like insulin are indeed protein-based, but the clearest and most straightforward example of a protein’s function in this context is transport demonstrated by hemoglobin.