Biological membranes Flashcards
What is the main function of cell membranes?
They provide barriers between different environments and contain many biomolecules
What does “amphipathic” mean in the context of membrane lipids?
It means a molecule has both hydrophilic (water-loving) and hydrophobic (water-fearing) parts.
What are the three major types of membrane lipids?
Phospholipids, glycolipids, and cholesterol.
What is the basic structure of a phospholipid?
A polar (hydrophilic) head group and non-polar (hydrophobic) tails.
What are the hydrophobic properties of membranes given by?
their fatty acids
Describe the structure of fatty acids
-Long hydrocarbon chains of various lengths and
degrees of unsaturation
– Terminate with carboxylic acid groups
What are the 3 major kinds of membrane lipids?
-Phospholipids–>contain phosphate residue(s)
– Glycolipids – contain sugar residue(s)
– Cholesterol
What can lipids spontaneously form?
closed biomolecular sheets in aqueous media which are barriers to the flow of polar molecules
What are phospholipids derived from?
-glycerol (a 3-carbon alcohol) or
-sphingosine (a more complex alcohol)
What is the difference between phosphoglycerides and sphingolipids?
Phosphoglycerides are derived from glycerol, while sphingolipids are derived from sphingosine
What are phospholipids derived from glycerol called? What does it consist of?
phosphoglycerides–> glycerol backbone, two fatty acid chains and a phosphorylated alcohol
What is the basic structure of phospholipids?
polar (hydrophilic)
head group and non-polar (hydrophobic) tails
What are glycolipids?
Sugar-containing lipids, like cerebroside.
What is the role of cholesterol in cell membranes?
It regulates membrane fluidity, preventing fatty acid crystallization and blocking large motions.
How does thin layer chromatography help us study membrane lipids?
It separates different lipids based on their affinity for a stationary and mobile phase
What is an example of a glycolipid?
cerebroside
Describe glycolipid structure
sphingosine backbone, fatty acid unit linked via
amide bond, and primary hydroxyl group of
sphingosine esterified to glucose or galactose
What is Cholesterol?
a sterol present in eukaryotes but not in most
prokaryotes
Which places are rich in cholesterol and which areas typically have smaller amounts?
Plasma membrane is rich in cholesterol
* Membranes of organelles typically have
smaller amounts
What does TLC separate?
Separates different lipids based on their relative
affinities for a stationary phase (silicic acid) and a
mobile phase (organic solvents).
What are the three possible arrangements of phospholipids in an aqueous medium?
Micelles, liposomes, and lipid bilayers.
