Membrane Structure Flashcards
Of the other macromolecules, are lipids larger or smaller?
Smaller.
Are membranes composed of just lipids?
NO, proteins AND lipids
What does amphiphatic mean?
It means it has a hydrophilic and hydrophobic end.
Are all membrane lipids amphiphatic?
YES
What is the major component of membranes?
Phospholipids… more specificalls phosphoglycerides.
What are some examples of hydrophilic head groups?
serine (AA), inositol (sugar), choline
What is the difference between glycerides & galactides and sphingolipids?
Their backbones. glycerides and galactolipids have glycerol as their backbone while sphingolipids have sphingosine.
What class are the greatest number of lipids? What is their general function?
Sphingolipids, they function as cell signals.
Are triglycerols amphiphatic?
NO they are NOT. Since their head is also a fatty acid (hydrophobic) the entire molecule is hydrpophobic.
Where are galactolipids commonly found?
Plant membranes
Do glycolipids and phosphoilipids have a type with a sphingo or glycerol backbone?
YES
How and where are fatty acids synthesizes?
By fatty-acid synthase in the cytosol of the liver.
How are triglycerols transported? Where from?
VLDL
from the liver through blood to other tissues
Where are triglycerols stroed?
adipose tissue
How are triglycerols broken down? what is the purpose of this?
By lipases
for energy or to use the fatty acids for membrane lipid synthesis
Where in the cell are membrane lipids synthesized and how are they then transported?
Synthesized in the smooth ER
1 - trnasported via vesicles
2 - transported via carrier proteins
3 - membrane to membrane contact in the same cell
Name the 3 ionic and 1 polar head group of phospholipids that we discussed in class.
Ionic: phophatidylcholine, phosphatidylserine, and phosphatidylethanolamine
polar: phosphatidylinositol
Describe the differences between a saturated fatty acid and an unsaturated fatty acid.
Saturated - saturated with H, no double bond, linear tail
Unsaturated - not saturated with H, contain a double bond. If cis then they have a kink but if they are trans they are not kinked.
What is a liposome?
This is when PLs where observed in vitro to form spheres.
Are phosphoglycerides mobile as a part of the membrane?
YES, the can move around to fill in tears and gaps in the membrane.
What are some dietary examples of unsaturated and saturated fats?
cis unsaturated: vegetable oils (liquid at room temp)
trans unsaturated - hydrogenated vegetable oils (solid)
Saturated: Butter (solid at room temp)
What do cholesterols do for the cell membrane?
They can be inserted into the membrane to stiffen it, filling the gaps formed by unsaturated tails.
Which is more fluid, saturated or unsaturated?
Unsaturated
What is Describe the role of scramblase and flippase.
Scramblase - when new phospholipids are formed in smooth ER, this enzyme catalyzes the transfer of random PLs from one monolayer to another.
Flippase - When new membrane lipids arrive from ER to the golgi flippase helps in transferring SPECIFIC PLs to the CYTOSOLIC monolayer of the new membrane, this is also present in the plasma membrane.
Are PLs evenly distributed in the ER? What about the golgi, PM, and other compartments?
YES
and
NO
What is the purpose of adding sugars to the glycolipids of the lumen of the golgi? Is this process reversible?
This prevents them from being flipped, ensuring that they remain on the outside surface of the cell, coating and protecting the cell.
This process is reversible, can be glyosylated.
Can changes in one phospholipids composition, including asymmetry of one cell, have an effect on another neighboring cell?
YES
What molecules pass through the bilayer more easily? Which ones dont?
Easily: small molecules, nonpolar molecules
Less easily: larger. charged or polar
What is the main function of the bilayer?
to be selectively permeable by allowing only specific charged or large molecules to pass through it.
What are four different ways that proteins associate with membranes?
Transmembrane - implanted throughout the entire bilayer.
Monolayer - implanted in one of the layers
Lipid-linked - linked to a lipid head
Protein attached - linked to a membrane implanted protein
What are 4 different functions of membrane proteins we discussed in class?
- Transporters and channels
- Anchors
- Receptors
- Enzymes
Are the proteins and lipids of the membrane fluid or static?
fluid, can diffuse in any direction of plane of membrane
Can the thickness of the bilayer of a cell vary?
YES
What is a lipid raft?
These are protein-PL-cholestrol interactions that form a cluster.
Describe the fluidity experiment and what it showed about PLs.
This is where two cells with two different labeled and dyed membrane proteins were fused, after being fused the labels appeared to be randomly dispersed throughout the hybrid cell from where they initially fused.
What are some things that may limit the mobility of membrane proteins?
- tethered to the cytoskeleton
- tethered to the ECM
- tethered to proteins of another cell
- Diffusion barriers present on membrane limit mobility. LIKE TIGHT JUNCTIONS
How can fluorescence recovery after photobleaching (FRAP) help to measure mobility of membrane proteins?
First you fluorescently label the membrane proteins, then you bleachan area with a laser, after this is done the unbleached proteins will move into the area of the bleaching, eventually the area will be filled in with new unbleched proteins completely making it hard to even tell the area was bleaching.
