Chapter 11 Membranes Flashcards
What are the two functions of cholesterol?
At high temps is prevents a cells from being too runny
In cold weather is prevent gel state
How much of a plasma membrane is cholesterol?
20-30%
Where is the bilayer built?
Smooth Er
Where is the bilayer refined and processed?
In the golgi, fliapase turns the lipids over so that
What are the functional classes of membrane proteins?
anchors, receptors, enzymes, ion channels and transporters
What types of proteins are in the plasma membrane?
transmembrane, monolayer assoicated alpha helix, lipid linked, protein attached
What is a phospholipid composed of?
A hydrophilic head and two hyrdophobic tails. For example, phosphatidylcholine has a choline as it hydrophilic head, it is the most common phospholipid in cell membranes
Why can’t hydrophobic molecules bind?
Because they are uncharged and non-polar
How do hydrophilic molecules bind to water?
electrostatic attractions or hydrogen bonds
Water happens to water that surrounds hydrophobic molecules?
They organize into cage-like structures. Because this cage like structure is more highly ordered than the rest of the water, its formation requires free energy.
Are lipid bilayers self sealing?
yes, any tear in the sheet exposes hydrophobic molecules to water which is energetically unfavorable are quickly closed.
If the tear is small the spontaneous rearrangement will eliminate the water, If the tear is large, the sheet may being to fold in on itself and break up into separate closed vesicles.
No matter what, interaction between water and the phospholipid bi-layer is quickly eliminated.
This self-sealing mechanism is essential to life.
Do the lipids of the bilayer change places?
The aqueous environment prevents lipids from escaping the bilayer, but the lipid molecules of move around within the bilayer, this causes the bilayer to behave like a fluid
What properties affect how tightly hydrocarbon tails can pack?
The bonds and the length
What are model phospholipids called?
liposomes
