In this video, we're going to introduce porins, which are found in the outer membrane of gram-negative bacteria. These porins are integral membrane proteins that are integrated into the outer membrane of gram-negative bacteria. They help to facilitate passive transport of molecules across the outer membrane. These porins span the entire membrane as cylinder-shaped pores, creating an entire passageway or a tunnel through the outer membrane to allow molecules to diffuse across passively. Porins always have identical subunits and are found in the outer membrane, forming in groups of three. You'll see these three identical subunits that associate with each other to form the entire porin structure.

If we take a look at this image below, we're showing you a gram-negative bacterial cell, focusing specifically on its outer membrane. You can see the lipopolysaccharides that are embedded here, and you can also see the porins themselves, which are these cylindrical-shaped pores. These porins form in groups of three, with units of three that associate with each other to create a pathway for molecules to diffuse across passively. When you zoom into the structure of the porin, you can see how it consists of these three subunits. They associate with each other to allow for passive diffusion. Here's a top view that shows how these cylindrical-shaped subunits come together to create the pore for specific molecules to diffuse across.

This concludes our brief introduction to these porins, and we'll be able to get some practice applying this knowledge as we move forward. I'll see you all in our next video.