How are phospholipids categorized?
Based on their head group
What is a sphingolipid?
Phospholipid with a sphingosine instead of a glycerol
What are the functions of cholesterol?
- Stiffens membrane, making it less fluid and less permeable
- Prevents hydrocarbon tails of phospholipids from packing –> decreases crystal formation
In a fluid state, are there more saturated or unsaturated FAs?
Unsaturated FAs
In a gel-like state, are there more saturated or unsaturated FAs?
Saturated FAs
Define amphipathic.
Is both hydrophobic and hydrophilic
What are the features of the Fluid Mosaic Model?
- Proteins are not just arranged along the surface, but are also embedded in the lipid bilayer –> mosaic of lipids and proteins in the membranes
- Molecules including lipid and proteins can move laterally (are freely diffusing) in the membrane –> membrane is not solid, but more like a fluid
Are proteins static or dynamic?
Dynamic, for the most part
What is FRAP? Function?
Fluorescence recovery after photobleaching = used to study lateral movements of proteins w/in the membrane
How does FRAP work?
- High-powered laser is used to bleach a particular region in a cell expressing the protein of interest –> region loses its fluorescence
- W/ time, unbleached protein moves in and bleached protein moves out of region –> gains back its fluorescence
How can you tell how fast a protein is moving using FRAP?
- Fluorescence recovers fast –> protein is very dynamic
- Fluorescence recovers slow –> protein is very stable and anchored in place
What is a single pass membrane? What does it look like on a hydrophobicity plot?
- Protein that passes through membrane one time
- Plot: only one peak above 0 (in hydrophobicity range)
What is a multipass membrane protein? What does it look like on a hydrophobicity plot?
- Protein that passes through a membrane multiple times
- Plot: as many peaks above 0 as there are passes through the membrane
What is a lipid/GPI-anchored membrane protein?
Protein made inside the cell, but displayed outside the cell and anchored to membrane by a GPI anchor
Where and when does acylation occur?
2nd position of a protein after synthesis is complete
Which terminus is away from the membrane in acylation?
C-terminus
Which terminus is away from the membrane in prenylation?
N-terminus
What is a giveaway that prenylation has occurred?
CxxC (cysteine sandwich)
What does trypsin do?
Chops up the extracellular domains of any proteins imbedded in the plasma membrane
What is the effect of trypsin treatment on western blot analysis of that protein?
After treatment, only the parts of the protein inside the membrane will remain –> protein will be smaller and move toward the (+) anode faster
Glucose is moved into intestinal epithelial cells against its concentration gradient using the potential energy of _____ established through the _____.
- Na+ ion gradient
- Na+/K+ ATPase pump
You isolate a loss of function mutation in a bacterial gene that codes for a fatty acid desaturase. You are now proposing to analyze membranes from this mutant strain of bacteria. What do you expect to find?
A decrease in the number of carbon double bonds and a decrease in membrane fluidity.
