Final answer:
Proteins are built from amino acids through protein synthesis, controlled by genes. While the body can produce most amino acids, nine essential ones must be obtained from the diet. After proteins are constructed and utilized within the body, they are degraded and their amino acids recycled.
Step-by-step explanation:
How Proteins are Built
Proteins are essential polymers made from amino acids and are necessary for various functions within the body. The process of protein synthesis begins with the linking of amino acids into a polypeptide chain, which occurs rapidly at a rate of 3-5 amino acids per second, in a process controlled by genes. This chain grows until it forms a complete protein, which then undergoes various modifications to become fully functional.
The human body can produce most but not all of the twenty amino acids; there are nine essential amino acids that must be ingested through our diet. Proteins consumed in the diet are broken down during digestion into free amino acids, which are then absorbed and used to synthesize new proteins in the body. These new proteins can have structural roles, act as antibodies, or regulate cellular activities.
After a protein is synthesized, it does not last long in the body; it is eventually degraded and its amino acids are recycled. This process of degradation and recycling is crucial for maintaining bodily functions and for the production of energy, especially in circumstances like chronic starvation.