1. Which amino acid does not have a chiral center? a) glycine b) alanine c) thre
ID: 575884 • Letter: 1
Question
1. Which amino acid does not have a chiral center? a) glycine b) alanine c) threonine d) histidine e) asparagine 2. At pH = 6.9, which phosphates would be predominant (For HP04, pKal-22, pKa2-69, pKa.- 12.4)? a) HaPO4 and H2PO b) H:PO and HPO2 c) HPO2 and PO d) All of the above 3. Choose a polar neutral acidic acid. b) d) HN-CH-C-OH H2N-CH-C-o H2 CH2 OH NH 4. The amino acid lysine has pKa values of 2.2,9.0, and 10.5. Which of the following does not represent an effective buffer pH range that can be achieved when you use lysine as buffer? c) 7.0 a) 2.0 b) 3.0 d) 8.0 e) 9.3 5, what is the predominant form of aspartic acid at pH 7 (pkal = 2.0, pKa2-39, pK.,-99)? b) H3N H2 OH 0 6. Which amino acid will be buried inside a protein when the protein is dissolved in H:0 a) Lysine b) Threonine Phenylalanine d) Asparagine egltamateExplanation / Answer
(1)
Glycine does not have a chiral center because it has 2 H-atoms attached to the C-atom, thus it is optically inactive.
(2)
Since the given pH value is equal to the second dissocation pair, so the predominant phosphates are H2PO4- and HPO42-.
(4)
The pH value of 7 does not fall in any of the three buffer ranges, because a buffer range is one unit either side of the pKa value.
(5)
The correct option is shown in option (b), because when pH is greater than the pKa value of the group, then that group is present in dissociated form, according to the Henderson Hasselbach equation.
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