Cell Membranes Flashcards
How do sphingolipids differ from phospholipds?
Sphingolipids have a sphingosine backbone whereas a phospholipid has a glycerol backbone.
What is the liquid crystalline phase?
The cis-bonds in phospholipids prevent them from packing close together as they have kinks which cause them to branch out. This creates space within the bilayer which allows it to move freely.
How does low temperatures affect the crystalline structure?
Low temperatures can cause the acyl chains to freeze which limits the fluidity of the membrane.
What is an entropic process?
A process that involves a loss of order.
The formation of a bilayer is an entropic process? True or False
True, there is a decrease in order when the membrane forms , similar to protein folding.
How do membrane proteins insert themselves into a bilayer?
In order to pant themselves into a bilayer, the proteins must cross the hydrophobic core. It does this by forming an alpha-helical structure.
How doe transmembrane proteins anchor themselves into the bilayer?
The R groups of the proteins stick out and anchor into the bilayer.
A single transmembrane protein is enough to support the movement of a polar molecule across the membrane. True or False?
False, there has to be a cluster of transmembrane proteins that produce a polar route for molecules to cross.
What does cholesterol do in the membrane?
Cholesterol controls the fluidity of the membrane.
At low temperatures, cholesterol decreases fluidity, True or False?
False, at low temperatures, cholesterol makes the membrane more fluid y preventing the close packing of the flexible fatty tails.
Flip-flopping is energetically favourable, True or False?
False, flip-flopping is energetically unfavourable because it requires the movement of the polar heads to get to the oither side of the membrane.
What is the difference between an integral protein and a peripheral protein?
A integral protein spans the entire lipid bilayer. A peripheral protein is not embedded into the bilayer, instead it is attached to one side of the membrane.
What is the effect of cholesterol at high temperatures?
At high temperatures, cholesterol decreases fluidity of the membrane because of its rigid structure.
How does a ligand gated ion channel work?
When the gate is closed, the leucine faces inwards. Acetylcholine then binds to receptors on the channel protein, which causes it to rotate. The leucine now faces outwards and the serine faces inwards, causing a conformational change. This makes the centreof the channel protein hydrophilic so ion can move through.
What are the limitations of x-ray crystallography?
It is hard to form the protein crystals and determining the path of the x-ray after diffraction.
What are the limitations of electron microscopy?
It has a low resolution and requires 2D crystals.
What are the types of NMR?
Solution state - limited to the size of proteins that can be studied.
What is the primary difference between the types of protein samples used in X-ray crystallography and in NMR spectroscopy, and how does this difference introduce distinct limitations to each method?
In x-ray, you can study any sized protein but in NMR, the size is limited to 100kDa.
Difficult to obtain protein crystals for x-ray crystallography and in NMR the proteins must be in a high concentrated solution, which may not work with all proteins.
