A protein coat, also known as a capsid, is a protective layer made of proteins that surrounds the genetic material of a virus. This coat plays a crucial role in the virus's ability to infect host cells, as it helps the virus attach to and enter the cells. The structure of the protein coat can vary widely among different viruses, influencing how they interact with their environment. The protein coat is essential for the stability and integrity of the virus. It protects the viral genetic material from degradation and helps the virus evade the host's immune system. Understanding the structure and function of protein coats is important for developing vaccines and antiviral treatments.