1. Proteins

2. Objectives Write the general formula for an amino acid. Write the general formula for an amino acid. Define a peptide bond and write a formula that shows what this bond looks like. Define a peptide bond and write a formula that shows what this bond looks like. Define and show the relationship between a protein and polypeptide. Define and show the relationship between a protein and polypeptide. Define essential amino acids and complete proteins. Define essential amino acids and complete proteins.

3. Objectives Write formulas and/or structures that will illustrate what is meant by primary, secondary and tertiary structure of a protein. Write formulas and/or structures that will illustrate what is meant by primary, secondary and tertiary structure of a protein. Explain what denaturation is and how it can be produced. Explain what denaturation is and how it can be produced. Describe at least two human diseases that result from improper protein nutritional practices. Describe at least two human diseases that result from improper protein nutritional practices.

4. Protein “Prime importance” Found in: Cells (2/3 of dry cell weight ) Tissues All body fluids except urine and bile Not stored for future use (like carbohydrates and lipids)

5.  Proteins  Major components of: Skin, nails, claws, hair, wool, feathers, hooves, muscles, tendons and cartilage.

6.  Proteins  Essential Functions  Support (keratin/collagen)  Enzymes (specific catalysts)  Transport (channel proteins/hemoglobin)  Defense (antibodies)  Hormones (regulatory - insulin)  Motion (actin/myosin)  Motion (actin/myosin)

7. Protein Composition Polymers Amino Acid Monomers 20 amino acids in proteins

8. Amino Acids R C H C NH 2 O OH acid group amino group

9. Amino Acids Some are chemically neutral. Glycine has 1 carboxyl group and 1 basic group.

10. Amino Acids Some are chemically “acidic.” Glutamic acid has two carboxyl groups only 1 amino acid.

11. Amino Acids Some are chemically “basic.” Lysine has two amino groups and 1 carboxyl.

12. Amino Acids Differ in nature of R group.

13. Amino Acids Some are hydrophobic.

14. Amino Acids Some are hydrophilic.

15. Peptide Two or more amino acids bonded together. AA X

16. Peptide Bond Covalent bond between amino acids. Electrons shared unevenly (O 2 is more electro- negative than N 2 ). Polarity permits hydrogen bonding between parts of a polypeptide.

17. Polypeptides Chains of many amino acids joined by peptide bonds. Proteins may contain more than one polypeptide chain. Can have large numbers of amino acids. Since amino acids differ by R group; proteins differ by a particular sequence of the R groups.

18. Protein Functions Enzymatic Structural Storage Transport Hormonal Receptor Contractile Defensive Regulatory Sensory

19. Enzymatic Action Enzyme (sucrase) Substrate (sucrose) Fructose Glucose OH H O H2OH2O

20. Protein Structure Shape determines function. Shape determines function. Animation: Protein Structure Introduction Animation: Protein Structure Introduction

21. Interactions and Protein Shape Hydrogen bonds Disulfide “bridges” Ionic bonds Van der Waals attractions Hydrophilic/hydrophobic reactions

22. Interactions and Protein Shape

23. R group of cysteine ends with a sulfhydryl group (-SH) Enables one chain of amino acids to connect to another by a disulfide bond (-S-S-). Interactions and Protein Shape

27. Levels of Protein Structure Primary The specific sequence of amino acids joined by peptide bonds. Animation: Primary Protein Structure Animation: Primary Protein Structure

28. Primary Structure Historical Perspective -Fredrick Sanger determined first protein sequence (insulin). -Broke into fragments and determined AA sequence of fragments. -Then determined sequence of fragments. -Required ten years research; modern automated sequencers analyze sequences in hours.

29. The specific geometric shape caused by intramolecular and intermolecular hydrogen bonding. Levels of Protein Structure Secondary Animation: Secondary Protein Structure Animation: Secondary Protein Structure

30.  Helix Discovered by Linus Pauling and Robert Corey. Oxygen partially ─, hydrogen partially +. Hydrogen bonding between the C=O of one AA and the N-H of another. Hydrogen bonding between every fourth AA acid holds spiral shape of an alpha helix. In keratin  helices covalently bonded by disulfide (-S-S-) linkages between two cysteine amino acids. Levels of Protein Structure Secondary

31.  Pleated Sheet Polypeptides turn back upon themselves Hydrogen bonding between extended lengths. keratin includes feathers, hooves, claws, beaks, scales and horns; silk Levels of Protein Structure Secondary

32. F olds or creases –Beta ribbon –Greek Key –Omega loop –Helix-loop-helix –Zinc finger –Helix-turn-helix –Beta hairpin Levels of Protein Structure Motifs

33. Greek Key 4 beta strands folded over into a sandwich shape. It is named for its resemblance to the Greek key meander pattern in art.

34. Omega Loop Named after its shape, the Greek capital letter Omega Consists of a loop of any length and any amino acid sequence.

35. Helix-Loop-Helix Two α helices connected by a loop. Some of these facilitate DNA binding.

36. Zinc Finger Protein (blue) containing three zinc fingers in complex with DNA (orange). The Zinc ions are green. (Transcription Factors)

37. Helix-Turn-Helix Binds to major groove of DNA through hydrogen bonds and various Van der Waals interactions with exposed bases. Two α helices joined by a short strand of amino acids Found in many proteins that regulate gene expression.

38. Beta Hairpin Two beta strands that look like a hairpin. Beta strands are adjacent in primary sequence and oriented in an antiparallel arrangement in the hairpin

39. Result when proteins of secondary structure are folded, due to various interactions Between R groups of their constituent amino acids. Levels of Protein Structure Tertiary Animation: Tertiary Protein Structure Animation: Tertiary Protein Structure

40. Results when two or more polypeptides combine. -Hemoglobin is globular protein with a quaternary structure of four polypeptides. -Collagen is a fibrous protein consisting of three polypeptides coiled like a rope - Most enzymes have a quaternary structure. Levels of Protein Structure Quarternary Animation: Quaternary Protein Structure Animation: Quaternary Protein Structure

42. Sickle-Cell Disease Slight change in primary structure can affect a protein’s structure and ability to function Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin.

43. Chaperone Proteins Special proteins which help new proteins fold correctly. –Chaperone deficiencies may play a role in facilitating certain diseases.

44. Denaturation Of Proteins Loss of normal configuration – a physical change. Once a protein loses it normal shape, it cannot perform its usual function. Sometimes will “renature.”

45. How Proteins Can Be Denatured Temperature Cooking an egg Albumin congeals Addition of hydrogen or hydroxide ions (large pH changes) Adding acid to milk Causes curdling Vigorous Shaking Organic Solvents Salts of heavy metals (mercury, silver & lead) Detergents Ultraviolet Radiation

46. Essential Amino Acids Dietary requirements Not synthesized

47. Essential Amino Acids methionine or cysteine leucine isoleucine lysine phenylalanine (or tyrosine) threonine, typtophan valine

48. Complete Proteins Proteins that contain all essential amino acids. They are usually derived from animal sources.

49. Protein Deficiency Diseases Marasmus & Kwashiokor Two of the most common children’s diseases worldwide.Two of the most common children’s diseases worldwide. Weaned diet deficient in protein.Weaned diet deficient in protein.

50. Kwashiokor Sufficient calories, insufficient protein.Sufficient calories, insufficient protein. SymptomsSymptoms –Loss of appetite –Diarrhea –Enlarged liver –Pigmented skin –Apathy –Irritability –Bloated belly

51. Marasmus Inadequate calories and proteinInadequate calories and protein Symptoms similar to KwashikorSymptoms similar to Kwashikor –Swollen belly –Loss of muscular tone –Rough, leathery skin –Generally retarded physical and mental development