Cell Biology
An Introduction to Cell Biology Membranes: Basic Structure Page [1 of 2]
I hope you guys are getting the idea that membranes are important. Membranes are unbelievably important when it comes to the study of the eukaryotic cell. Everything we talk about, membranes are going to be involved. I’m trying to be gentle with this vocabulary, but there’s no way we can get around it. When I refer to things, when biologists refer to things, it’s like a classification system. You guys know the whole story of why we call things by their scientific name. Well, it’s the same thing with cell parts. There’s a vocabulary that goes with the cell, and you’re just going to have to tough it out and learn it. But you know what? It makes sense. Learn to dissect those words. Now, the plasma membrane in an animal cell, or in a plant cell, separates the cell from its exterior, but the membranes in the cell also separate the parts of the membrane in closed organelles from the environment of the cell. Well, when we talk about some of the functions of membrane, we’re going to refer to the cytosol and the cytoplasm, and let’s just get those words out of the way. The cytoplasm is what we refer to as all of the material inside of the cell between the plasma membrane and the nucleus. So, for example, you will find many organelles in the cytoplasm, and the cytoplasm has a liquid in it called the cytosol – “cyto” solution. “Cyto” means cell. So we have the cytoplasm, kind of plasma; cytosol is the solution in the cytoplasm. Cell membranes, plasma membranes, and membranes in general can have other functions too. Now, here’s an interesting one. These are what are called microvilli – and we’re going to talk a lot about those later on – but you can see that you can actually have cytoplasmic extensions of the cell membrane. So what you have here is the plasma membrane extending itself