1. Introduction to Proteins

2. What do proteins do? Structural proteins Function: Support
Example: Collagen and elastin provide a fibrous framework in animal connective tissues such as tendons and ligaments
Keratin is the protein of hair, horns, quills,
Keratin
Collagen injection

3. What do proteins do? 2) Storage Proteins
Function: Storage of amino acids
Example: Ovalbumin is the protein of egg whites
Casein is the protein is mammal milk

4. What do proteins do? Transport Proteins
Function: transport other substances
Example: hemoglobin transports oxygen from the lungs to the other parts of the body
Other proteins transport molecules across cellular membranes

5. What do proteins do? 4) Hormonal Proteins
Function: coordination of bodily activities
Example: Insulin helps control the concentration of sugar in blood
Insulin

6. What do proteins do? Receptor Proteins
Function: response of cell to chemical stimuli
Example: neuron receptors respond to chemicals released by other nerve cells

7. What do proteins do? Contractile proteins Function: Movement
Example: Actin and myosin are the proteins responsible for muscle movement

8. What do proteins do? Defensive Proteins
Function: Protection against disease
Example: Antibodies combat bacteria and viruses

9. The Immune System

10. What do proteins do? Enzymatic Proteins
Function: Speed up chemical reactions
Example: amylase hydrolyzes sugar polymers in food.

11. What is a protein? A protein is a linear chain of amino acids
20 species of amino acid, properties dictated by side chain (R)
Polar (hydrophillic): contain O and N
Nonpolar (hydrophobic)
Acidic: negative charge
Basic: positive charge H
NH3+ C
COO- R

12. Amino Acids

13. How Complex are Proteins?
Example: Average E. Coli protein:
300 a.a. long
20 possible a.a. at each position
=20300 possible sequences!
DNA: structure is independent of sequence
Protein: structure change with sequence change

14. Polypeptide Chains
Enzymes join the carboxyl of one amino acid to the amino group of another amino acid
Amino acids are joined in a condensation reaction to form a peptide linkage
Polypeptides range in length from a few monomers to thousands of amino acids long

15. Peptide linkage

16. Protein Composition Peptide Bond Amino Acid Subunit
Proteins are composed of amino acids covalently linked via polypeptide bonds
Peptide Bond
Amino Acid Subunit R O R C NH C C NH NH C C NH C C O R O R

17. Protein Have Multiple Levels of Structure
Primary
Secondary
Tertiary
Quaternary

18. Protein Have Multiple Levels of Structure
Primary
Unique sequence of amino acids
Even a slight change can affect the proteins ability to function
For example: The disease sickle cell anemia is caused by glutamic acid changing to valine at position 6

19. Sickle Cell

20. Proteins Have Multiple Levels of Structure
Secondary
a-helices, b-sheets, turns, and random coils
Controlled by hydrogen bonding network

21. Protein Have Multiple Levels of Structure
Tertiary
Interaction of pieces of secondary structure
Controlled by side chain interactions and include hydrogen bonds, ionic bonds, hydrophobic interactions, and covalent bonds in the form of disulfide bridges

22. Protein Have Multiple Levels of Structure
Quaternary
Interaction of multiple chains
Interactions are controlled by shape and chemistry
Hemoglobin

23. Hemoglobin An example of quarternary structure