Final answer:
Protein is the nutrient essential for building and repairing tissue in the body, providing structure to tissues and organs, and serving as enzymes and antibodies. It is critical during periods of rapid growth and for the healing process, such as bone repair. Proteins are made of amino acids, which are vital for producing new cells and carrying out the body's chemical processes.
Step-by-step explanation:
The nutrient that plays the most critical role in building and repairing tissue is protein. Proteins are crucial for the development and maintenance of all body tissues, not just muscle. They provide the structure and function of the body's tissues and organs and perform the chemical work of cells. Proteins are composed of amino acids, which are arranged in chains and folded into complex shapes that determine the protein's specific function. These amino acids are vital for creating new cells, including those involved in bone repair and growth, particularly during periods of rapid development such as infancy and adolescence.
Moreover, proteins also serve as enzymes facilitating bodily functions and as antibodies that protect the body from pathogens. A steady intake of proteins is thus essential to sustain proper physiological processes and promote healing, such as fracture repair. It is crucial to note that protein also provides energy and is important in the composition of other macromolecules like nucleic acids central to genetic information.