Membrane Architecture I: The Fluid Mosaic Model Flashcards
Define that the Fluid Mosaic Model, models.
A model that describes the behavior of the non-covalently held together mixture of lipids and proteins. (Cell membrane!)
Define what the Lipid Bilayer is, and how lipids and proteins move (diffuse) through it.
The lipid bilayer is a thin, two dimensional fluid.
Lipids and proteins are able to diffuse laterally through the membrane .
What are the diffusion coefficient for lipids? What about membrane proteins?
Describe how the membrane is asymmetric. What is the take away?
Lipids- dynamic asymmetry: the distribution of the types of lipids in the inner leaflet versus the outer leaflet can differ.
Peripheral and Integral Proteins- Absolute asymmetry: proteins, have an outside face and inside face, and they are embedded in the membrane at a particular orientation.
Glycosolation- mostly lipids and proteins on outer plasma membrane surface are glycosylated, whereas inner membrane, proteins and lipids or generally not.
** membranes are dynamic structures, membranes are not uniform throughout the cell**
Define the lateral diffusion. Hint: cell membranes have lateral diffusion.
Meaning in one leaflet lipids are able to move around freely same with with proteins. Note that this is not trans leaflet it can only stay in the leaflet It’s already in.
What is FRAP? What does it confirm? (Fluorescence recovery after photobleaching.)
Pretty much what they do is photobleach an area making it very apparent that this part of the lipid membrane is altered. And then they track that spot overtime and you noticed that the black spot eventually completely disappears. This signals that the lipids are diffusing across the membrane overtime and they are not stationary.
What can influence phospholipid membrane movement?
Temperature and lipid composition. This slide only talks about temperature. Another flashcards will be about lipid composition.
Higher temp = more movement (shocking-sarcasm)
How does lipid composition influence movement within phospholipid membranes relative to temperature?
The shorter the chain of a lipid(fatty acid) The lower, the melting point is going to be. (Aka less heat required for movement)
The longer the chain of a lipid(fatty acid) the higher, the melting point is going to be. (Aka more heat required for movement)
How do membrane bilayers stay fluid enough for things to diffuse, but not too fluid that too many things get in and out of the cell?
They quantify changes in molecular composition with changes in environment. Meaning they change the types of lipids within their membrane.
Low temps: Lot more unsaturated fats
High temps: lot more saturated fats
Note: Eukaryotes use this but not as much as Cholesterol
Cholesterol “plasticizes” phospholipid membranes. What does this mean? What is the function?
It means cholesterol makes the membrane fluidity less variable with temperature.
What role does cholesterol play in membrane organization?
Cholesterol can fill in gaps of large lipids. But cannot form its own by layer as it’s too hydrophobic.
Note: and they create a microdomain, which will be another flash card.
Explain what microdomain cholesterol is a part of. What other molecule is needed for this domain and what is the entire domain called and its function.
These domains have about 3 to 5 times the amount of cholesterol as the surrounding membrane. And about 50% more sphingolipids as the surrounding membrane.
This leads to a more ordered and more thicker membrane.
These transcendently form (meaning not there all the time). And are platform sites for cellular signaling and membrane budding.
