water, molecular interactions, and acid-base chemistry Flashcards
dipolar nature of water
hydrogen atoms have localized partial positive charges and the oxygen atom has a partial negative charge
what is the structure of water
tetrahedral arrangement of electron pairs and hydrogen atoms around oxygen atom
hydrogen bonds
longer and weaker than covalent O-H bond
what is a hydrogen bond defined by?
defined by distance between acceptor and donor
how many hydrogen bonds are possible per water molecule?
four hydrogen bonds; where in liquid water average 3.4 H bonds and ice all 4 H bonds
why does ice have all 4 H bonds?
allows it to be more opened up, resulting in its density being less than liquid water
what is important for clathrate-like structures?
entropy effect
what is the lifetime of a hydrogen bond?
1-20 ps (10^-12 s); liquid water can be described as a “flickering structure”
hydrogen bond donors
N-H, O-H (not C-H)
hydrogen bond acceptors
N: and O:
what differentiates a functional folded protein from a precipitated protein?
only 10 kJ/mol
what is a factor for the strength of a hydrogen bond?
stronger when 3 atoms involved like in a line
amphipathic
both hydrophilic and hydrophobic
what are some of the characteristics of long-chain fatty acids?
very hydrophobic alkyl chains surrounded by a layer of highly ordered water molecules
what stabilizes the micelle?
energy gained by freeing immobilized water molecules
the water concentration is combined with the equilibrium constant forms what?
acid dissociation constant, Ka
what is a buffer?
consist of an aqueous solution of a weak acid and its conjugate base
what is the henderson-hasselbalch?
pH= pKa+ log[A-]/[HA]
pepsin
digestive enzyme secreted into gastric juice, which has pH of approx. 1.5
trypsin
digestive enzyme that acts in the small intenstine and has a pH optimum that matches the neutral pH in the lumen of the small intestine
alkaline phosphatase of bone tissue
hydrolytic enzyme thought to aid in bone mineralization
