Topic 4: Membrane Structure Flashcards
Structure of phosphoglyceride
glycerol head. Considered primary structural backbone of the membrane. Unsaturated fatty acids make it difficult to pack together b/c of kinks. Fluidity increased.
Glycolipid structure
The head group is simple complex sugar. Functions in recognition and protection beyond the simple membrane structural role.
Structure of sphingolipid
based on serine instead of glycerol. The head group is glycerol and choline. Made inside the Golgi.
How does cholesterol fit into membrane?
Fills in space created by kink of unsaturated fatty acids t
Why is cholesterol considered a fluidity buffer?
the phospholipid to which it is most attached displays reduced mobility. Resist changes in the fluidity of membrane. Increases stiffness of the membrane at high temperatures. More fluid at lower temperatures.
What factors affect membrane fluidity?
Temperature: more fluid at higher temperatures.
Lipid composition: Unsaturated fatty acid have kinks reduces packing and increases fluidity. Sterol content buffers fluidity and increases stiffness at high temps.
What are lipid rafts?
microdomains of membrane material mostly cholesterol, spingolipids and glycolipids. More unit through the membrane. Serve as a base for specific proteins.
Membrane components found only outside the cell
Sphingomyelin and glycolipids. Made in golgi outside. Cholesterol found on both sides.
Dos the lipid bilayer have the same composition on both sides?
No, the membrane is not always constant. Composition of membrane is not set in stone
Integral proteins
Embedded in bilayer. Regions projecting out in on both sides. receptors and transporters. Extraction destroys membrane.
Peripheral membrane proteins
Stick to the sides of membrane. Ionic interactions with lipid head groups don’t touch hydrophobic tails. Non covalent interactions with integral membrane proteins
Lipid linked proteins
Hang from the membrane by their lipid tail. Covalently linked to a modified fatty acid like molecule
Why is it important that an alpha helix anchored membrane proteins has consecutive hydrophobic amino acids?
Because all the amino acids are hydrophobic
Which class of integral membrane proteins can form channels through the cell membrane?
Amphipathic tunnel. Multiple amphipathic helix passing through the membrane.
G proteins coupled receptor
Nothing goes through protein. Binds on outside leads to changes on inside.
Two ways peripheral proteins can associate with the membrane
1) anchored to the plasma membrane by intramolecular forces
2) positively charged amino acids which interact with phosphate head groups
What must a lipid-linked proteins contain that allows it to associate with the inside of the phospholipid bilayer?
anchored in the plasma membrane by covalently attached fatty acid tails
Why does it make sense to sometimes limit the mobility of membrane proteins?
Regions of the plasma membrane can have separate and specific functions
