Natalie Pemberton-Parris 00027917

CHEM 121 – Amino acids and Proteins (32mks)

1. In an amino acid, the carbon atom with four groups attached to it (amino, carboxylic, hydrogen and R group) is called an - carbon. (1mark)

2. How is an aliphatic amino acid different from a hydroxyl containing amino acid? (2mks)Aliphatic amino acids contain C & H are non-polar because; the hydroxyl amino acids are polar and contain OH group.

3. How are the acidic amino acids different from their amines? (2 marks)Because the Amine has an amino group (Nh2) and the acidic have the OH group.

4. How are the aliphatic amino acids different from aromatic amino acids?(2 marks)Aliphatic, whose carbon atoms are joined together in straight or branched open chains rather than in rings while aromatic has rings in the structure.

5. How is proline different from other amino acids? (2 marks)All other amino acids the R groups are bonded to the carbon atom. However, in Proline the R group is bonded to the Carbon atom as well as the nitrogen group.

6. The bond which links amino acids together is called a Peptide bond. (1mark)

7. Draw the structure of the following tripeptide: (5 marks)

8. What is the primary structure of a protein? the linear sequence of its amino acid (1 mark)

9. What does the primary structure of a protein determine? It determines how protein folds (2mark)

10. List the three main types of secondary structure. (3 marks)1. helix2. pleated sheet3. turn

Ala-cys-lys

11. Name the linkage which maintains all three secondary structures. Hydrogen bonding (1mark)

12. How is the linkage in question 11 different between the -helix and -turn? (2 marks)In the -helix the hydrogen bonding occurs every 4 resides and in the -turn they occur ever 3 resides.

13. How is the linkage in question 11 different between parallel and antiparallel -pleated sheet? (2 marks)In parallel beta sheets the bonding is slanted and in the antiparallel they are straight. The terminals are on the same side on the parallel beta sheets but opposite on the antiparallel beta sheets.

14. Name the chemical interactions which stabilize the tertiary and quaternary structures. ( (4marks)Hydrophobic interactions, Hydrogen bonds, Electrostatic interactions and Disulfide bonds.

15. In the tertiary structure of a protein the chemical interactions occurs between the R groups (side chains) of amino acids (1mark)

16. What is the quaternary structure of a protein? (1 mark)Quaternary Structure is the combination of two or more polypeptide chains, to form a complete unit.