Final answer:
Elastin, an elastic protein found in connective tissues, allows those tissues to stretch and return to their original shape. It is crucial for the functioning of various structures in the body.
Step-by-step explanation:
Elastin, an important elastic protein found in all connective tissues, allows those tissues to stretch and return to their original shape. This property of elastin is essential for the functioning of various structures in the body. For example, in the walls of large arteries, elastin allows the arteries to expand and contract with each heartbeat, maintaining proper blood flow. In the lungs, elastin helps the air sacs stretch during inhalation and recoil during exhalation, aiding in the process of breathing.