Cell Identity

00:01 Now we should take a look at some of the specific cell labels.

00:07 Give a couple examples of these cell labels that you might see in the extracellular matrix.

00:12 Extracellular matrix, just matrix means stuff in general.

00:16 So on the outside we will see lots of glycoprotein tags, for example, when we are thinking about ABO blood typing.

00:29 Each of the A and B labels are glycoproteins that exist on the outside of the red blood cells.

00:36 So our body will know that it's our type blood. If we were to put type B blood into a type A person, then that type B blood would be recognized as foreign because the type A person doesn't have that label.

00:48 So glycoproteins are labels. Glyco means that it's got protein component and it also has glucose component.

01:00 The other class that we see are glycolipids. Again the sugar is directly attached to the glycolipids, those are more involved in communication of the cells.

01:12 So finally we can look at major histocompatibility proteins.

01:17 These are other labels that there's a lot of active research going on in it at the moment.

01:22 Major histocompatibility proteins identify "self" from "non-self".

01:28 So an example would be the sorts of things we see with the red blood cell and A and B labelling.

01:33 Or in the immune system, we may sometimes see there are cancer cells or invading cells that are not displaying self labels.

01:42 These major histocompatibility proteins are made by our immune system to identify invaders.

01:50 It's a very active area of research currently.

01:53 But simply they're cell labels, identifying "self" from "non-self". We call them MHC proteins.

02:02 So some cells interact so closely because they are part of the same tissue and they need to actually physically be connected to each other.

02:11 So that's where the simplest form of connection will be seen with these cadherin based junctions.

02:19 This is an example of where we have a single transmembrane domain or two of them, one from each cell and they connect with each other.

02:30 You can see that in the example here, the lower cell membrane has a single pass protein and it's attached to an actin molecule. So one of the cytoskeletal elements.

02:41 That way, that protein is held stably in the membrane and it can associate with a similar protein on its neighbouring cell.

02:49 And so these cadherin based junctions, being anchored to the cytoskeleton allow cells to connect to each other.

02:58 So very simple junctions but many of the other junctions that we'll explore will be based on the same kind of concept.