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BCH 400 exam 1 Ellison questions with complete solutions
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BCH 400 exam 1 Ellison questions with complete solutions
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BCH 400 exam 1 EllisonAn object is alive if: - correct answer ✔✔1. uses energy from some source to drive chemical rxns
2. reproduces
3. undergoes evolution
all life on Earth: - correct answer ✔✔-nucleic acid as hereditary molecule
-same genetic code
-same AA to make proteins
-1 or more cells
-complex organism
-evolution
Why is life carbon based? - correct answer ✔✔-C forms single, double, triple bonds
-bonds w/ H,N,S,O,P & others
Ochem performed by living systems is highly stereospecific - correct answer ✔✔-generally only deal with
1 stereoisomer not mix
geometric isomers - correct answer ✔✔cis or trans
-diff physical + chem properties
enantiomers - correct answer ✔✔mirror images around chiral centers
-identical physical (except polarized light)
-react identically with achiral reagents
diastereomers - correct answer ✔✔non-mirror around chiral ctr
-diff physical + chem properties
,living organisms exist in a dynamic steady state and are never @ equilibrium w/ surroundings - correct
answer ✔✔-energy coupling
-biological catalysts
-entropy inc= creating and maintaining order requires energy
how to speed reactions up: - correct answer ✔✔-inc. temps (stability of macromolecules is limiting)
-inc. concent. of reactants (costly)
-change rxn by coupling to a fast one (universally used)
-lower activation barrier by catalysts (universally used)
Miller & Urey in 1953 - correct answer ✔✔demonstrated that organic compounds could form under
primitive conditions
van der waals - correct answer ✔✔-attractive force (London dispersion) depends on polarizability
-repulsive force (steric repulsion) size of atoms
-attraction dominates at longer distances
-repulsion at shorter
-weak individually
importance: determines steric complementarity, stabilizes biological macromolecules )stacking in DNA),
facilitates binding of polarizable ligands
hydrophobic effect - correct answer ✔✔-association/interaction of nonpolar molecules in aqueous sol
-main factor behind: protein folding, protein-protein association, formation of lipid micelles, binding of
steric hormones to their receptors
-does NOT arise b/c of some attractive force b/w 2 nonpolar molecules
How hydrophobic effect happens - correct answer ✔✔-nonpolar portions of amphipathic molecule
aggregate so fewer molecules are ordered= entropy inc.
-micelles, bilayer, vesicles
, hydrophobic effect favors ligand binding - correct answer ✔✔-binding sites in enzymes + receptors are
often hydrophobic
-displace water= inc. entropy
-drugs take advantage of hydrophobic effect
h bonds - correct answer ✔✔-strong dipole-dipole interactions
-strongest when bonded molecules allow for linear bonding
-not unique to water
water is medium for life - correct answer ✔✔-protection from UV (life evolved in water)
-organisms= 70-90% water
-chemical rxns occur in aqueous
-structure of water molecule: sp^3, octet, H bond donor+acceptor
-water: high BP, MP, large surface tension
-good solvent for polar molecules, bad for nonpolar
solutes change properties of water: colligative properties - correct answer ✔✔-BP, MP, osmolarity
-do not depend on nature of solute, just concentration
solutes change properties of water: noncolligative properties - correct answer ✔✔-viscosity, surface
tension, taste, color
-depend on chemical nature of solute
osmotic pressure - correct answer ✔✔high conc. to low conc.
proton hopping - correct answer ✔✔protons do not exist free in solution
what does a high Ka mean? - correct answer ✔✔-low pH
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