1. Proteins

2. Proteins Most structurally and functionally diverse group:
Structural material
Enzymes
Transport molecules
Cell communication
Defense
movement
General structure of an amino acid (building block)

3. Proteins
There are 20 different R-groups in living organisms and therefore 20 different amino acids
See page for the various R group structures

4. Proteins
Amino acids join together to form polypeptides through condensation reactions
The bond is called a peptide bond:

5. Polypeptides can only be built in one direction
They have an N-terminus (NH2) and a C-terminus (COOH)
A series of amino acids is called a polypeptide chain

6. Proteins
Of the 20 amino acids, 8 are considered to be essential because humans cannot produce them; they must be consumed
The word protein suggests that a polypeptide chain has gone through several degrees of structural changes to become a final product
There are 4 structural levels in the creation of a protein

7. Proteins Primary (1º) Structure The order of amino acids in a chain
The sequence of amino acids is determined by the genes that “coded” for it
Structure determines function!
Consider sickle cell anemia

8. Sickle cell anemia results from one single amino acid substitution at the 6 position (6th AA)

9. Proteins Secondary (2º) structure
The H-bonds among the amino acids form alpha- helices or beta-pleated sheets

10. Proteins Tertiary (3°) Structure
Interactions between distant amino acids create “whole molecule” folding
Hydrophobic Interactions: cytoplasm is water-based, so hydrophobic amino acids cluster away from water
H-bonds and ionic bonds may form
Disulfide bridges form between sulfur groups. These interactions anchor the 3D shape of the protein

11. Proteins

12. Proteins Quaternary (4°) structure:
Clustering of two or more tertiary polypeptides through hydrophobic interactions
Polypeptides then become a functional protein

13. Proteins
Protein denaturation: the unfolding and destruction of protein functionality
Causes: pH, salinity, temperature
These can disrupt disulfide bonds, H-bonds, and ionic bonds
The 3D shape is altered
Some proteins can return to their functional shape after, but some cannot

14. Proteins
Try these:
P.50 #19, 20, 22, 23, 24, 25,