AS CW- function of protein in the membrane- help please :)

Hey ! Am at the the moment doing my biology coursework on the function of proteins in the plasma membrane and am struggling to find any information that I can understand other than what I have (which is listed next to the bullet point), on:
-proteins as ahesion sites- help similar cells stick together.
-proteins as enzymes- help speed up reactions at the membrane
-proteins as recognition sites- identitfy similar cells
I could do with more information on how they do that function and maybe some examples and diagrams. Any help is much appreciated, Thankyou :smile:

! (by the way this is as level) xxx

Reply 1

Teacher_of_Bio

Hey

their are 3 main reasons why proteins are found in the membrane

The first is for cell turgidity (in other words, cell structure and support).Many proteins are vital in maintaining the shape of the cell.

2nd is for cell to cell recognition. Proteins are found on the surface of cells as "glycoproteins". These are made of carbohydrate molecules and protein molecules. The recognition proteins allow interaction between cells and allow one cell to "recognise" the other cell. This recognition then leads to interaction between the cells allowing the cells to join or transfer molecules between each other for example.

The 3rd reason is for transport of nutrients and macromolecules (small molecules)
Proteins in the cell membrane allow for certain molecules to be taken into the cell. They span (fit across) the whole of the membrane.
These form "protein channels" kind of like bridges inside the membrane. They allow molecules to pass through the membrane inside this protein channel.
The proteins are selective, in that they only allow certain molecules into the cell.
it is also an example of active transport becasue they transport molecules against a concentration gradient i.e. from an area of low concentration outside the cell to an area of high conc. inside the cell (it requires energy)

(more detail, the membrane spanning proteins have hydrophilic ends (both at the end which is on the outside of the membrane and at the end on the inside) They also have a hydrophobic middle part which means they can integrate into the cell membrane phospholipid bilayer)

Reply 2

Suzannnne!!

Thanks a lot that makes quite a lot of things clearer esp. the bit about cell recognition, I have already got quite a lot on the transferring of substances across the membrane, although I realise that I didn't make that clear in the first post. Thanks once again!! Any more help is welcome! xxx

Reply 3

magda.ulaan

Hi,

I want to add some functions of membrane proteins:
* As a hormone binding sites: a site exposed on the outside of the membrane allows one specific hormone to bind.
* Enzymes located in the membranes either catalyse reaction inside or outside the cell, depending on whether the active site is on the inner or outer surface.
* Electron carriers are arranged in chains in the membrane so that electrons can pass from one carrier to another.