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Bio Chem Quiz 2
| Question | Answer |
|---|---|
| what are the nonpolar aliphatic amino acids (7) | Gly, Ala, Val, Leu, Ile, Met, Pro |
| what are the aromatic amino acids (3) | Phe, Tyr, Trp |
| what are the polar uncharged amino acids (5) | Ser, Thr, Cys, Asn, Gln |
| what are the positive amino acids (3) | Lys, Arg, His |
| what are the negative amino acids (2) | Asp, Glu |
| what is the behavior of nonpolar aliphatic amino acids | they have hydrophobic cores; they are mostly C-H surfaces that avoid water and pack into protein interiors |
| what is the behavior of aromatic amino acids | they are rings; UV of 280 nm, they do packing; they are large, electron-rich, and often partly hydrophobic |
| what is the behavior of polar uncharged amino acids | they do H bonds, leading to modifications; they usually do not carry a full charge at pH 7, but they make hydrogen bonds and create specificity |
| what is the behavior of positive amino acids | they make salt bridges and are nucleic acids; |
| what is the behavior of negative amino acids | they make salt bridges and are metal and active sites |
| what is special about Val, Leu, and Ile | they are bulky hydrophobic packing |
| what is special about Ala | it is a small hydrophobic placeholder |
| what is special about Pro | it is a rigid ring that often bends the chains, introducing kinds, and it disrupts helices |
| what is special about Met | it is sulfur-containing but still nonpolar |
| what is special about Phe | it is a hydrophobic packing |
| what is special about Tyr | it can hydrogen bond through the OH |
| what is special about Ser and Thr | they have alcohol groups that are phosphorylation sites |
| what is special about Asn and Gln | they are H-bond donors and acceptors |
| what is special about Cys | it is a thiol, so it can form a disulfide bond and it has redox-sensitive links |
| what is special about Lys and Arg | they are predominantly positively charged at pH 7 and often interact with negative partners such as phosphate groups, carboxylates, and nucleic acids |
| what is special about His | its side-chain pKa is near physiological range, so its charge is especially sensitive to local environments and it often acts as a reversible proton donor and acceptor in active sites |
| what is special about Asp and Glu | they commonly form salt bridges, coordinate metals, and participate in catalytic acid-base chemistry |
| what is special about Gly | it does not have a chiral center; it is the smallest amino acid, it is flexible, and fits tight turns |
| what are the two equations to find pH | pH = -log {H+} and pH = pKa + log {A-/HA} |
| what is the equation to find pKa | pKa = -logKa |
| what three things does water do | it is polar and H-binds, it stabilizes ions, and competes for H+ |
| what four things does charge control | solubility, binding, catalysis, and protein folding |
| one unit of pH change __________ | is equal to a 10-fold change in {H+} |
| lower pH means what | more acidic, more H+ available for binding |
| higher pH means what | more basic, less H+ available for binding |
| what is pKa | the pH where HA+A- ; the molecules "hold-on-to-H+" tendency |
| what is favored when pH<pKa | protonated form is favored (HA) |
| what is favored when pH>pKA | deprotonated form is favored (A-) |
| what does it mean when pH=pKa | it is at the transition point, HA+A- |
| low pH ____ H+, high pH _____ H+ | adds; removes |
| if pH is one unit lower than pKa, what are the percentages of HA and A- | HA is about 90%, A- is about 10% |
| if pH is equal to pKa, what are the percentages of HA and A- | HA and A- are both about 50% |
| if pH is one unit about pKa, what are the percentages of HA and A- | HA is about 10% and A- is about 90% |
Created by:
olivia.baierl