Question

10. The peptide shown has the amino acid sequence: A. Val-Ser-Ile-Glu-Lys B. Lys-Glu-Ile-Ser-Val C. Thr-Asp-Leu-Gln-Arg D. Val-Asp-Ile-Glu-Arg 11. Which of the following describes the entire three- dimensional structure of a single polypeptide? A. Secondary structure B. Quaternary structure C. Tertiary structure D. Primary structure 12. What is the primary driving force in the formation of protein tertiary structure? A. Energy released when additional ion pairs are formed. B. The exclusion of non-polar substances from aqueous solution. C. The formation of van der Waals interactions between neighbouring groups. D. Energy released when additional hydrogen bonds are formed. 13. Which of the following series of amino acids is most likely to be buried in the center of a water-soluble globular protein? A. Ala, Leu, Phe B. Pro, Gin, His C. Glu, Asp, Lys D. Gly, Asn, Ser

Answer 1

Answer-

10) The peptide shown has the amino acid sequence of A) Val- Ser- Ile- Glu- Lys.

valine is an amino acid which has hydrophobic side chains. Serine is polar uncharged amino acid, Isoleucine has hydrophobic side chain, Glutamate has negatively charged side chain and lysine has positively charged side chain.

cool coo cool + 1 HIN-C-H + 1 . N-C-H N -C -H H-C-OH H-C+CH₃ сH TH CH2 HC CH₂ valine serine •CH3 Isoleucine Coo Coo AN-C-H H2N-C-H CH₂ CH2 CH₂ CH2 CH₂ cool CH2 Slutamate NH₃ Rysine

11) Tertiary structure describes the entire three dimensional structure of a single polypeptide. Some proteins contain two or more polypeptide sequences or chains, which form querternary structure.

12) d) Energy released when additional hydrogen bonds are formed is the primary driving force in the formation of protein tertiary structure.

Amino acids which are far apart in the polypeptide sequence, their side chains are involved in bond formation among themselves to form three dimentional structures. These interactions include hydrogen bonding, disulfide bonds etc.

13) A) Ala-Leu-Phe amino acid residues are most likely to be buried in the center of a water soluble globular protein.

Alanine, leucine amino acids have hydrophobic side chain, phenylalanine has aromatic side chain. These side chains do not interact to polar water. On the other hand amino acids with negatively side chain (glu, asp), positive side chains ( Lys, Arg, His) and polar side chains (Ser, Thr, Cys, Asn, Gln) interact to polar water molecule.