{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture 3 - Lecture 3 Cellular Membranes Do the lipids and...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 3 Cellular Membranes Do the lipids and proteins in the membrane interact and does the very location of a protein, is it regulated by the lipids and do the lipids move to places where there are particular proteins? In other words, are the lipids and proteins in the any membrane talk to each other? Answer is yes. Gorter and Grendel Experiment They want to know the real structure of the membranes and what they did was they took red blood cells (great because when they matured, they have nothing but membrane on the outside) and extracted all the lipids and they lay them out on a tray of water. All the lipids were pushed together and then they measured the area and what they found when all the lipids were spread out, they have twice the area that you would get if you just took a cell and measure the area of the membrane. So they concluded all the lipids in the membrane form a bilayer. Davson Danielli model proposed that the membrane has a layer of proteins on the outside, a layer of proteins on the inside and lipid bilayer in between. But there’s a thermodynamic problem with this model; it required that the polar portions of membrane lipids be in contact with the non-polar portions of membrane proteins. Lipids and proteins will try and arrange themselves with the least amount of energy (hydrophobic will move away from water and hydrophilic will move toward water). In DD model, the proteins would put their nonpolar surfaces close to the polar portion of the lipids while putting their polar portions in an aqueous environment. Fluid Mosaic Model Instead of the protein forming a solid layer, they are intersperse within the lipid bilayer. Use of cell fusion to demonstrate membrane fluidity One characteristic of membrane is that membranes are fluid. The lipids and proteins can move in the plane of the membrane. One experiment they did to prove this was they fuse human cells and mouse cells. Now human cells and mouse cells have very different membrane proteins. After they are fused together, the human and mouse proteins have intermixed themselves in the membrane and the only way this could have happened is if they sailed pass each other. Now it is true that a protein sunk in the membrane cant move very long distances. Frap Proteins are labeled with fluorescent dye. The membrane would bleach when you shine a very sharp beam of light on it. After a few minutes, you find recovery. Why? Labeled proteins here have drifted into the bleached area. Helper T cell and B cell
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
In the immune system, two cells come together and they interact. The receptors on the membrane surface have to find each other. Receptor 1 has to be close to receptor 2 and therefore for their function, proteins have move to a very particular place.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}