Block 2 Lecture 18 Flashcards
what is the covalent bond energy between hydrogen and oxygen
500 kJ/mol
what is the hydrogen bond energy between hydrogen and oxygen in water
20 kJ/mol
what is the hydrophobic effect
tendency of non polar molecules to self associate in water rather than to dissolve individually driven by the loss of hydrogen bonding and the higher entropic cost of forming a cavity around non polar molecules
what does the hydrophobic effect stabilize
the structure of biological membranes
what are the 2 principle constituents of membranes
lipid and protein
what are phosphates made of
a 3 carbon glycerol compound, 2 fatty acid tails, negatively charged phosphate head groups (such as serine, choline, inositol, enthanolamine and glycerol
what are the steps of bilayer synthesis
- enzymatic synthesis of phospholipid
- insertion of phospholipid into cytoplasmic face of SER
- distribution of phospholipids across ER membrane by means of an ATP dependent flippase
what is cholesterol considered
a sterol
what are sphingolipids composed of
2 fatty acid tails, a polar head group built on a sphingosine backbone
what are peripheral membrane proteins
include many cytoskeletal proteins, involved electrostatic interactions, easy to strip membrane of peripheral proteins by increasing salt concentration
what are lipid rafts
collections of closely packed sphingolipids and cholesterol that form rafts which specific proteins attach within the membrane bilayer
what do thiolreactive reagents and HG2+ do
selectively block the facilitates water flux in aquaporins leaving cell membranes with a permeability close to that of a lipid bilayer
what are some characteristics of aquaporins
have a 3A pore for water to pass through, an amino acid near narrow part of pore is cysteine, if replaced with alanine water permeability is no longer sensitive to Hg2+ because Hg2+ attacks the sulfur atom in cysteine
