STPM Biology - chapter 1: Reision essay question 18

18. Describe briefly the primary, secondary and tertiary structures of proteins. State the importance of these structures which are related to the properties of protein. [11]


Answer:

Primary structure:
- sequences of amino acid in the polypeptide chain
- polypeptide chain consists of amino/ N-terminal and carboxyl/ C-terminal
- numbering of sequence starts from N-terminal
- the amino acids are linked by peptide bonds
- total amino acids/ R-group/ side chain/ functional group determine protein to be basic,
acidic or neutral/ soluble/ insoluble
Secondary structure:
- depends on hydrogen bonds
- produces α-helix and β-pleated structures
- α-helix give high elasticity/ cylindrical structure/ coiled in the helical structure
- β-pleated is for padding and cushion
- both structures may be present in a protein

Tertiary structure:
- depends on disulfide bridge/ bonds
- hydrophobic interaction/ bond, ionic bond and van der waals effect
- forming globular structure/ protein conformation/ folding
- 3-dimensional structure gives/ determines biological activity
- protein denaturation occurs when tertiary structure is broken/ destroyed

Assignment submitted by H. L., Lim, H.P., Tan, S. Y., Tan, H.S., Teow, A.M., Chia 2011/2012 (IBM)