Porin is a type of protein that forms channels in the membranes of cells, particularly in bacteria and mitochondria. These channels allow the passage of small molecules and ions, facilitating essential processes like nutrient uptake and waste removal. Porins are crucial for maintaining the cell's internal environment and supporting cellular functions. In bacteria, porins are found in the outer membrane and help regulate the entry of substances, contributing to antibiotic resistance. In mitochondria, porins play a role in energy production by controlling the flow of metabolites. Overall, porins are vital for cellular health and function across various organisms, including bacteria and eukaryotic cells.