MCB1 - Focus On Membrane Biology Flashcards
Define hydrophilic, hydrophobic and amphiphilic.
Hydrophilic - water loving.
Hydrophobic - water fearing.
Amphiphilic - contains both hydrophilic and hydrophobic region.
Discuss hydrophobic effect.
Self organisation of amphiphilic molecules to minimise exposure of hydrophobic areas to water.
Two types of diffusion in lipid bilayers. Which is less energetically favourable.
Lateral diffusion - movement of phospholipids left and right.
Transversal diffusion - flipping of phospholipids from inner to outer leaflet.
What factors affect membrane fluidity.
Lipid composition. Protein composition. Cholesterol. Temperature.
What enzymes aid transversal diffusion.
Flippase or sramblase enzymes.
Do saturated or unsaturated fatty acids increase membrane fluidity.
Unsaturated fatty acids have kinks in their structure so cant pack as close together and so increase membrane fluidity.
Discuss effect of temperature on membrane fluidity.
Increasing temperature increases membrane fluidity as molecules move more.
Discuss effect of cholesterol on membrane fluidity.
Cholesterol functions as a buffer, preventing lower temperatures from inhibiting fluidity and preventing higher temperatures from increasing fluidity.
What types of molecules can freely cross a lipid bilayer.
Hydrophobic molecules. Some small uncharged polar molecules.
What types of molecules can not cross a lipid bilayer unaided.
Ions.
What are the types of phospholipids in mammalian membranes.
Phosphatidylethanolamine. Phosphatidylserine. - contains negative charge. Phosphatidylcholine. Sphingomyelin. Sphingosine (not a phospholipid).
What molecules do prokaryotes have less of in their plasma membrane.
Cholesterol and glycolipids.
How does cholesterol increase membrane fluidity.
Inserts between phospholipids reducing their packing and so increases membrane fluidity.
What is the role of glycolipids in plasma membranes.
Involved in cell signalling.
Discuss asymmetric distribution in lipid bilayer.
Specific molecules are found only on the inner or outer leaflet. E.g phosphatidylserine found only on inner leaflet. Glycolipids found only on outer leaflets.
