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Fig. 22-CO, p. 551

CHAPTER 14 PROTEINS. Fig. 22-CO, p. 551. Transport Structural Storage Catalysis . Hormones Receptor Contractile Defensive. PROTEIN FUNCTIONS. AMINO ACIDS. Chirality of Amino Acids. Nonpolar side chains (at pH 7.0). Polar side chains (at pH 7.0).

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Fig. 22-CO, p. 551

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  1. CHAPTER 14 PROTEINS Fig. 22-CO, p. 551

  2. Transport Structural Storage Catalysis Hormones Receptor Contractile Defensive PROTEIN FUNCTIONS

  3. AMINO ACIDS

  4. Chirality of Amino Acids

  5. Nonpolar side chains (at pH 7.0)

  6. Polar side chains (at pH 7.0)

  7. Acidic and basic side chains (at pH 7.0)

  8. Nonpolar • Polar • Charged

  9. Although -amino acids are commonly written in the un-ionized form, they are more properly written in thezwitterion(internal salt) form.

  10. Carboxylic acid Amine Amide

  11. Proteins are polymers of Amino Acids joined by peptide linkages

  12. Peptides • Peptide: A short polymer of amino acids joined by peptide bonds; they are classified by the number of amino acids in the chain. • Dipeptide: A molecule containing two amino acids joined by a peptide bond. • Tripeptide: A molecule containing three amino acids joined by peptide bonds. • Polypeptide: A macromolecule containing many amino acids joined by peptide bonds. • Protein: A biological macromolecule containing at least 30 to 50 amino acids joined by peptide bonds.

  13. Writing Peptides • By convention, peptides are written from the left, beginning with the free -NH3+ group and ending with the free -COO- group on the right. • C-terminal amino acid: the amino acid at the end of the chain having the free -COO- group. • N-terminal amino acid: the amino acid at the end of the chain having the free -NH3+ group.

  14. Primary Structure • Primary structure: the sequence of amino acids in a polypeptide chain. • The number peptides possible from the 20 protein-derived amino acids is enormous. • there are 20 x 20 = 400 dipeptides possible. • there are 20 x 20 x 20 = 8000 tripeptides possible. • the number of peptides possible for a chain of n amino acids is 20n. • for a small protein of 60 amino acids, the number of proteins possible is 2060 = 1078

  15. Primary (1º) Structure

  16. Secondary Structure • Secondary structure: conformations of amino acids in localized regions of a polypeptide chain. • The most common types of secondary structure are a-helix and b-pleated sheet. • a-Helix: a type of secondary structure in which a section of polypeptide chain coils into a spiral, most commonly a right-handed spiral. • b-Pleated sheet: a type of secondary structure in which two polypeptide chains or sections of the same polypeptide chain align parallel to each other; the chains may be parallel or antiparallel.

  17. Secondary (2º) Structure results from hydrogen bonding between along the backbone

  18. a-Helix • The C=O group of each peptide bond is hydrogen bonded to the N-H group of the peptide bond four amino acid units away from it.

  19. MYOGLOBIN

  20. b-Pleated Sheet • The C=O and N-H groups of peptide bonds from adjacent chains point toward each other and are in the same plane so that hydrogen bonding is possible between them.

  21. 3-D PROTEIN MODELS

  22. Tertiary Structure • Tertiary structure: the overall conformation of an entire polypeptide chain. • Tertiary structure is stabilized in five ways: • Covalent bonds, as for example, the formation of disulfide bonds between cysteine side chains. • Hydrogen bonding between polar groups of side chains, as for example between the -OH groups of serine and threonine. • Salt bridges, as for example, the attraction of the -NH3+ group of lysine and the -COO- group of aspartic acid. • Hydrophobic interactions, as for example, between the nonpolarside chains of phenylalanine and isoleucine. • Metal ion coordination between 2 side chains with the same charge, linked through an ion.

  23. Hydrogen Bonding • Polar side chains -OH -NH2 - NH2 -SH

  24. HYDROPHOBIC INTERACTIONS • Nonpolar side chains

  25. IONIC INTERACTIONS • Charged side chains

  26. DISULFIDE BONDS • Cysteine residues

  27. Hormone released by pituitary gland that causes uterine contractions. Insulin

  28. s s s s s s s s s s s s Reducing Agent Oxidizing Agent

  29. METAL ION COORDINATION • Side chains linked through • interaction with a metal

  30. Tertiary Structure

  31. 3º Structure 2º Structure 1º Structure

  32. QUATERNARY (4º) STRUCTURE • The arrangement of subunits to form a larger protein. Hemoglobin

  33. DENATURATION Native state Denatured state

  34. Heat Acids/bases • Organic solvents • Detergents • Metals

  35. MAD COW DISEASE • Bovine • Spongiform • Encephalopathy (BSE) • Creutzfeldt-Jakob • Scrapie

  36. leucine proline

  37. ALZHEIMERS • Alois Alzheimer first reported symptoms in 1906 • The two principal changes • Plaques - deposits of protein called beta amyloid. • neurofibrillary tangles- malformations of the protein tau within nerve cells.

  38. Plaques - amyloid precursor protein (APP)—Protein that is normally an essential component of the brain. Plaques are made when an enzyme snips APP apart at a specific place and then leaves the fragments--beta amyloid--in brain tissue where they come together in the spaces between neurons and form abnormal deposits.

  39. Neurofibrillary Tangles - Tangles are twisted fibers inside the neurons caused by changes in a protein called tau

  40. Plaques and tangles block the normal transport of the electrical messages between the neurons that enable us to think, remember, talk and move. As AD progresses, nerve cells die, the brain shrinks, and the ability to function deteriorates.

  41. SICKLE CELL ANEMIA SICKLE CELL NORMAL

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