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23 Cards in this Set
- Front
- Back
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Molecular Weight of Water
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18
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Unique Physical Properties of Water
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() for low MW, very high melting point, boiling point, surface tension
() ice less dense than liquid H2O () solvent for hydrophilic and amiphipathic compounds |
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BrØnsted-Lowry Theory
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ACIDS are proton donors
BASES are proton acceptors |
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Disassociation of STRONG acids or bases in water
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Completely disassociate
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Disassociation of WEAK acids or bases in water
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Do NOT completely disassociate
>can act as buffers |
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Henderson-Hasselbach Equation
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pH = pK + log ([A-]/[HA])
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Meaning of pK values
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The larger the value of pKa, the smaller the extent of dissociation
= ↑ pK = weaker acid |
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pK of a functional group
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the pH at which the group is 50% ionized
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Function of Buffers
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“buffer” pH changes
>release protons upon addition of base >accept protons upon addition of acid |
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Isomer of Amino Acids found in proteins
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L isomer
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Zwitterions
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ALL amino acids at pH 7
> bear positive and negative charge |
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pK of Amino Acid Groups
[ionization at pH 7] |
Carboxylic acid is LOW (3)
>deprotonated [COO-] Amino group is HIGH (8) >protonated [NH3+] |
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Three (3) Classifications for Amino Acids
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(1) Hydrophobic
(2) Polar (3) Charged - Acidic & Basic |
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Hydrophobic Amino Acids
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>interior of proteins
(1) Alanine, A (2) Valine, V (3) Leucine, L (4) Isoleucine, I (5) Proline, P (6) Phenylalanine, F (7) Tryptophan, W (8) Methionine, M (9) Glycine, G |
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Polar Amino Acids
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>R-group can H bond with H2O
(1) Threonine, T (2) Serine, S (3) Cysteine, C (4) Tyrosine, Y (5) Asparagine, N (6) Glutamine, Q |
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Charged Amino Acids
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>R-group can become ionized
(under normal condition= ionized) **THREE transitions in titrations** BASIC (1) Lysine, K (2) Arginine, R (3) Histidine, H ACIDIC (1) Glutamic Acid, E (2) Aspartic Acid, D |
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Environmental Modification of pK Values
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(i.e. as found in a protein)
the close proximity of an acidic residue to a basic residue will: ↓ pK of acidic residue (depro) ↑ pK of basic residue (pro) |
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Length of Peptide Bond
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1.32 Å
(planar) |
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β-mercaptoethanol
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breaks disulfide bonds
(used for denaturing proteins) |
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Denaturing Detergent
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Sodium dodecyl sulfate
>destroys the 2°, 3°, 4° structure >confers a negative charge |
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SDS-PAGE
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Sodium Dodecyl Sulfate -
Polyacrylamide Gel Electrophoresis >SDS=give (-) charge >migrate toward anode >smaller migrate more rapidly >stained with Commassie Blue |
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Migration Front
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furthest distance traveled by proteins in SDS-PAGE
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Analysis of SDS-PAGE
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(1) relative mobility
= distance protein traveled/ distance of migration front (2) Plot log molecular mass of Std. proteins vs. relative mobility |
