Protein- Secondary, Tertiary, and Quaternary Structure

1. Protein- Secondary, Tertiary, and Quaternary Structure

2. Levels of Protein Structure

3. Proteins Functions of Proteins: • Structural: Muscles, Antibodies • Hormones: insulin, thyroxin • Cell Transport Proteins • Enzymes are Proteins Central Dogma of Biology DNA mRNAProtein TranscriptionTranslation

4. Protein Building Blocks Amino acid structure: NH3 – C - COOH

5. R Groups • Nonpolar • Polar • Charged • + Charged • - Charged

6. Nonpolar R Groups

7. Nonpolar R Groups

8. Polar, but NOT Charged amino acids

9. Polar, but NOT Charged amino acids

10. Polar, Charged (Acidic) amino acids

11. Basic amino acids

12. Structure of R-group determines the chemical properties of the amino acid • The polar uncharged amino acids are hydrophilic and can form hydrogen bonds • The nonpolar amino acids are hydrophobic and are usually found in the center of the protein; they are also found in proteins which associated with cell membrane • The electrically charged amino acids have electrical properties that can change depending on the pH • Cysteine can form disulfide bond • Proline has a unique structure and causes kinks in the protein chain • When 2 amino acids are joined, the bond formed is called peptide bond

13. Building Proteins: The Peptide Bond

14. Peptide Bond OH CN You must be able to draw this bond, recognize this bond, and the significance of this bond.

15. Primary Structure of Proteins • The sequence of amino acids in the polypeptide chain • The sequence of R groups determine the properties of the protein • A change of a single amino acid can alter the function of the protein • Sickle Cell Anemia- caused by a change of one amino acid from glutamine to valine

16. Secondary Structure of Protein • Folding and coiling due to hydrogen bond formation between carboxyl and amino group of non-adjacent amino acid • These bonds occur between the BACKBONE of the strand of amino acids • R groups are NOT involved • Folding is due to the disulfide bond • Two common examples: alpha helix and beta pleated sheet

17. Secondary Structure of Protein

18. Folding due to Disulfide bond

19. Tertiary Structure of Protein • 3-D structure resulting from the folding of 2o structural elements • Stabilized by bonds formed between amino acid R groups • Form many shapes (globular compact proteins and fibrous elongated proteins)

20. Tertiary Structure of Proteins

21. Quaternary Structure of Protein • Multiple polypeptide chains bonded together • 3-D structure due to interactions between polypeptide chains • R-group interactions, H bonds, ionic interactions • Assembled after synthesis • Only proteins with more than one subunit can have a quaternary structure

22. Quaternary Structure of Protein

23. Denaturation • Environment change (increased heat, changes in pH) proteins can unfold or “denature” • Loss of dimensional shape loss of protein function • Sometimes able to refold back into it’s original conformation

24. Nucleic Acids DNA RNA

25. Nucleic Acids • 3 components to a nucleotide: a pentose sugar, a phosphate group, and a nucleotide base

26. Nucleic Acids (2 Common forms): • RNA (ribonucleic acid) • DNA (deoxyribonucleic acid)

27. DNA & RNA differ by the presence on an –OH group (RNA) or an H-group (DNA) on the 2’ carbon of the pentose sugar

28. DNA contains C, T, A, G RNA contains C, U,A, G

29. DNA: double stranded RNA: single stranded

30. When a DNA or RNA polymer is created, the bond is formed between 3’ –OH group and 5’ phosphate group  phosphodiester bond