SP-C, or Surfactant Protein C, is a protein that plays a crucial role in the lungs. It is part of the pulmonary surfactant, a substance that reduces surface tension in the alveoli, the tiny air sacs where gas exchange occurs. This helps keep the alveoli open and prevents them from collapsing, ensuring efficient breathing. SP-C is produced by type II alveolar cells in the lungs and is essential for normal lung function. Deficiencies or mutations in the gene responsible for SP-C can lead to respiratory diseases, such as surfactant dysfunction disorders, which can severely impact breathing and overall health.