Lecture 4: Membrane Structure and Function Flashcards
Most abundant membrane lipids are ____
phospholipids
Membranes are held together by ___ interactions
noncovalent
What two structures do lipids form?
What lipid types have a cylinder shape?
Normal phospholipids, PC, PS, PI, PG, sphingomyelin
What types of lipids have an inverted cone shape?
Lysolipids, acyl-CoAs, detergents
Which lipids have a cone shape?
Diacylglycerol, Phosphatidic acid, unsaturated PE, fatty acids, ceremide
What are the four types of lipid movements in a membrane?
Lateral diffusion, flexion, rotation, flip-flop
Name typical membrane proteins.
- Glycerophospholipids
– PS, PE, PC, PI
• Sphingolipids
– Sphingomyelin (SM)
- Cholesterol
- Glycolipids
How does cholesterol affect membranes?
- Presence decreases fluidity of nearby lipids (less permeable)
- Inhibits crystallization (lowers phase transition temperature)
What’s the structure of cholesterol?
How does cholesterol pack in lipids?
It packs between fatty acid tails of the hydrophobic core of a bilayer.
Glycolipids
- Special sugar-containing lipids
- Found exclusively on noncytosolic side
- Tend to self-associate (lipid rafts)
Functions of glycolipids
- protection of cell surface
- electrical effects
- cell recognition and adhesion
Glycolipid structure
They have a short carbohydrate chain covalently attached and this is exposed on the outer surface of the cell.
What are phospholipases?
A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances.
Lipid Rafts
- often rich in sphingolipids and cholesterol
- longer, saturated chains of sphingolipids cause membrane thickening
- arrangement recruits particular proteins and facilitates their transport or function as a group
How are lipid droplets formed?
Storage form of lipids, usually triacylglycerol cores and cholesterol esters surrounded by a monolayer with a few proteins. They are thought to form from a “swelling” of the ER.
Phospholipid assymetry
- SM, PC, and glycolipids in outer leaflet (nuetral)
- PE and PS in inner leaflet (charged, net negative)
What type of membrane protein is this?
Peripheral membrane proteins
What type of membrane protein is this?
PIG tail (GPI anchor)
What type of membrane protein is this?
Covalent lipid attachment
What type of membrane protein is this?
antipathic α-helix
What type of membrane protein is this?
β-barrel
What type of membrane protein is this?
Multipass α-helix
What type of membrane protein is this?
Single pass α-helix
Name three post-translational attachments to the membrane
Myristoyl anchor (14 carbons)
Palmitoyl anchor (16 carbons)
Farnesyl anchor (15 carbons)
Which residues are preferentially hydrophobic?
Preferentially hydrophobic residues: Leu, Ile, Val, Ala, Phe
Where are membrane-spanning beta barrels usully found in the cell?
bacterial, chloroplast, and mitochondrial membranes
What are some common detergents?
SDS, Triton X-100, ß-octylglucoside
What does CMC stand for?
Critical micellar concentration
How do detergents dissolve membranes?
Solubilization and reconstitution of a membrane protein
___ create diffusion barriers for lipids, creating cells ____ membranes on different sides of the cell
Tight junctions, asymmetrical
ex- epithelial cells
How does this protein shape the membrane?
Hydrophobic region of protein wedges into membrane, displacing lipid head groups and causing curvature
How does this protein shape the membrane?
protein is curved and can bind to lipid head groups causing membrane to curve with it
How does this protein shape the membrane?
protein binds to and therefor clusters lipids with big head groups, this induces curvature
