Cell Strx 1: Membranes & Organelles Flashcards
___ is topologically equivalent to the lumen of the ER and the lumen of secretory vessels.
The outside of cell
By mass, the lipid bilayer is roughly __% lipid molecules.
50%, can range from 25% to 75% lipids, with the other major component being proteins
What is the function of membranes?
- Establish specialized environments by creating a boundary between the inside and outside of a cell and by defining intracellular compartments/organelles
- Scaffold for protein complexes
In general, the majority of membrane lipids are _____ and ____.
Phospholipids (4 types) and sterol (cholesterol)
Why are glycolipids associated with the non-cytosolic leaflet?
Sugar groups are added in lumens
Phospholipids are synthesized in the ____
ER
Sphingolipid synthesis is begun in the ____ and completed in the ___
ER, golgi.
What effect do unsaturated fatty acid tails have on the membrane?
Less efficient stacking, inhibits movement
What roles does cholesterol play in the membrane? (3)
- Stiffens membrane
- Decreases permeability
- Inhibits phase change (phospholipids have tendency to congeal at cooler temperatures)
In what 2 ways do glycolipids partition in the membrane?
Only present on non-cytosolic leaflet, may partition preferentially into lipid rafts
What 4 functions do glycolipids serve in membranes?
- Protection (glycocalyx)
- Surface properties of membranes
- Cell identification
- Cell adhesion
Note: can serve as entry points for bacterial toxins
What is NANA?
N-Acetylneuraminic acid, a negatively charged saccharide
What are phosphatidylinositol phosphohlipids?
Lipids with a single inositol sugar that can be phosphorylated at different positions and a varying number of times. They participate in cell signaling through binding and activating various enzymes at the membrane surface.
What are glycolipids?
Lipids with a 4-14 sugar oligosaccharide added.
