Lipids and Membranes Flashcards
How did Langmuir determine the structure of lipid monolayers?
Langmuir demonstrated that long chain fatty acid molecules displayed the same area per molecule irrespective of the number of carbon atoms (∼20Å^2) from such observations he deduced that the films were monolayer thick, and were oriented at the water surface with their polar head groups (hydrophilic) in the water and the hydrocarbon chains (hydrophobic) nearly normal to the surface.
What are amphiphilic molecules (amphiphiles)?
Molecules that contain a polar head group (hydrophilic (high affinity for polar solvents such as water)) and a non-polar tail (hydrophobic (strong affinity for nonpolar solvents such as hydrocarbons)) which leads to a preferential molecular orientation at the air-water boundary/interface.
What properties are required for a stable lipid monolayer?
The hydrophobic part must be large enough to make the molecule insoluble in the subphase whilst the hydrophilic head group must have sufficient attraction to the solvent (e.g. water) to keep the molecules anchored at the interface and prevent thin film build up.
What is a polar molecule?
A molecule which has an uneven distribution of electrons between the covalently bonded atoms causing regions of the molecule to have different charges.
What properties of a lipid molecule increase layer stability?
A longer non-polar chain/tail and more polar head groups.
What is the compressed area of a single lipid (biomolecule that is only soluble in non-polar solvents)?
40Å^2, double that of a fatty acid as lipids have two carbon chains
What is a cell membrane?
Cell membranes are thin (∼5nm thick) phospholipid bilayer structures with their molecules in constant fluid-like motion. The cell membrane contains many proteins.
What is a phospholipid?
Phospholipids are a class of lipids whose molecule has a hydrophilic “head” containing a phosphate group and two hydrophobic “tails” derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule).
What percentage of cell membrane mass is contributed by proteins?
30-50%
Why do proteins stick to cell membranes?
Due to their hydrophobic exterior.
What is a monolayer of cell membrane called?
A leaflet
What are vesicles (liposomes) and what are they used for?
A spherical structure consisting of liquid or cytoplasm enclosed by a lipid bilayer. They are used to transport material within cells.
What is the difference between oils and fats?
Temperature.
When fluid-like, it’s called an oil.
When solid-like, it’s called a fat.
What is the difference between unsaturated and saturated fats?
Unsaturated fats contain one or more double bonds. There is one less hydrogen atom per carbon atom at double bonds.
