Gateway Technical College BIO 806-177 Lecture 3 : Amin o Acids: 1)There are only three naturally occurring amino acids that do not have EXACTLY one chiral center

1)There are only three naturally occurring amino acids that do not have EXACTLY one chiral center. Which are they?

1. 1. GLY, ILE, THR
   2. ALA, ILE, TYR
   3. ASP, GLU, GLY
   4. PHE, TYR, TRP
2. Which is the charge of the peptide EHK at pH=3, pH=5, and pH=7? a.     +1, +1, 0

b.  +1, 0, -1

c.     +2, +1, -1

d.  +2, +1, 0

3. Which of the following peptide sequences have NO spectroscopic signal at 280nm wavelength?
   1. NHYLK
   2. FEFDL
   3. WVIAS
   4. PYWGG
4. Which amino acid is chemically modified to form a key component of the connective tissue protein collagen?
   1. Lysine
   2. Serine
   3. Proline
   4. Cysteine
5. Which of the following sequences is cleaved by BOTH trypsin and chymotrypsin?
   1. MSFESTVL

   2. 

      AKSDYGRD
   3. DFGSRPGG
   4. EGHVVIKL
6. What is the sequence of the illustrated peptide?
   1. QGDF
   2. EGNF
   3. QADW
   4. EANW
7. Which amino acid substitution is MOST likely to disrupt the function of a protein?
   1. R to K
   2. W to S
   3. D to E
   4. I to L
8. Which post-translational modification is encoded genetically?
   1. Phosphorylation of a serine residue
   2. Formation of a disulfide bridge from two cysteine residues
   3. Acetyllation of a lysine residue
   4. None of the above
9. What is the delta G of FORMATION of a peptide bond?
   1. > 0
   2. 0
   3. < 0