Cell Bio: Chapter 11 Flashcards
(35 cards)
What are membranes made of?
Proteins and lipids.
What characterizes all membranes?
They are all amphipathic, and have a hydrophilic head and hydrophobic lipid tails.
Do membranes spontaneously form?
Yes; due to the hydrophilic heads interacting with water.
What are phospholipids?
A glycerol core with two hydrophobic lipid tails attached and a phosphate (or polar charged head group).
Why is cholesterol important?
It helps with the rigidity and fluidity of animal cell membranes.
What are glycolipids?
They contain two lipid tails, and a polar head group with a sugar (glyco) group attached.
How do tail lengths affect membrane permeability?
The longer the tails are, the less fluid a membrane is, and the shorter tails are, the more fluid it is.
How does saturation affect membrane permeability?
The more saturated lipids are, the less fluid a membrane is because the lipids can pack way more tightly due to double bonds causing kinks.
How does temperature affect membrane permeability?
The higher the temperature, the more fluid the membrane is.
What does cholesterol do to cell membranes when integrated?
It stiffens the bilayer, and makes it more rigid and less permeable (makes up 20% of lipids in animal membranes).
True/False: Phospholipids can move around the membrane, and diffuse laterally within the plane of the bilayer.
True; although they are generally not able to flip from one side to the other without an enzyme’s help.
How are new phospholipids synthesized in eukaryotic cells?
By enzymes bound to part of the ER membrane in the cytosolic side.
What is the function of scramblase?
Transferring random phospholipids to the opposite side of the bilayer (equalizes them on either side).
What is the function the flippase?
Specificclly flipping one type of phospholipid across the membrane in one direction (found in the Golgi or plasma membrane and help set up asymmetry).
How are membranes transported between different compartments in cells?
Using vesicles (what is in the cytosol always stays there during transport).
What are integral membrane proteins?
Proteins embedded in the membrane (require detergents to remove them).
What are peripheral proteins?
Proteins bound to other membrane proteins through noncovalent bonds (easily removed).
What are some ways integral membrane proteins can extend across lipid bilayers?
As a single or multiple Alpha helices, rolled up Beta sheets (Beta barrels).
True/False: Some membrane proteins are anchored to the cytosolic surface by an amphipathic Beta sheet.
False; they can be attached by an amphipathic Alpha helix.
What is the most common way for membrane proteins to span a membrane?
Alpha helics, whether used singly or in combination.
What is a heterokaryon?
A hybrid cell where two have been fused togehter; used for studying the movement ofr proteins from one cell to another.
What are some methods of restricting protein movement?
Tethering them to the cell cortex, extracellular matrix molecules, or proteins on the surface of another cell. Diffusion barriers can restrict proteins to a particular membrane domain.
What are tight junctions?
Barriers in epithelial cells that separate the apical side from the basolateral side. Prevents fluids from leaking between cells.
What is FRAP (fluorescent recovery after photobleaching)?
Labeling a small area on protein or lipid fluorescently, and observing the recovery of fluorescence in a microscope. If the lipids were recovered, the protein or lipid was mobile in the membrane.
