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Amino Acids

Amino Acids. The building blocks of proteins. Basics of Amino Acids. Contain an amino group and a carboxylic acid group There are 20 amino acids found in proteins They are classified as nonpolar, polar or acidic amino acids. Nonpolar Amino Acids. Glycine ( Gly ) Alanine ( Ala )

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Amino Acids

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  1. Amino Acids The building blocks of proteins

  2. Basics of Amino Acids • Contain an amino group and a carboxylic acid group • There are 20 amino acids found in proteins • They are classified as nonpolar, polar or acidic amino acids

  3. Nonpolar Amino Acids • Glycine (Gly) • Alanine (Ala) • Valine (Val) • Leucine (Leu) • Isoleucine (Ile) • Phenylalanine (Phe) • Methionine (Met) • Proline (Pro) • Tryptophan (Trp)

  4. Polar Amino Acids • Serine (Ser) • Threonine (Thr) • Tyrosine (Tyr) • Cysteine (Cys) • Asparagine (Asn) • Glutamine (Gln)

  5. Acidic Amino Acids • Aspartic acid (Asp) • Glutamic acid (Glu) • Histidine (His) • Lysine (Lys) • Arginine (Arg)

  6. Essential vs. Nonessential Amino Acids • Essential aa’s cannot be made by the body: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine • Functions: • Break down food, grow, repair body tissues, other bodily functions

  7. Essential vs. Nonessential Amino Acids • Nonessential aa’s include: alanine, asparagine, aspartic acid, and glutamic acid • These are made by the body • Conditional aa’s are only essential in the times of stress or illnesss and include: arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine

  8. What do I eat? • Complete proteins contain all of the essential aa’s • Include: eggs, milk, meat, fish, poultry • Incomplete proteins are deficient in one or more of the essential aa’s • Include: wheat, rice, oats, corn, beans, peas, almonds, walnuts, and soy

  9. Peptides • The linking of two or more amino acids forms a peptide • A peptide bond is an amide bond that forms when the COO- group of one amino acid reacts with the –NH3+ group of the next amino acid • 2 amino acids together are called dipeptides and 3 are called tripeptide

  10. Protein Structure • Primary – peptide bonds • Secondary – helix shaped • Tertiary – 3D shaped • Globular/Fibrous – compact, spherical shape • Quaternary – 4 subunits

  11. Primary Proteins • Example: Insulin • 2 polypeptide chains held together by disulfide bonds

  12. Secondary Proteins • Three types • Alpha helix • Coiled shape with hydrogen bonds between the N-H of the peptide bond of one loop and the C=O of the peptide bond in the next loop

  13. Secondary Proteins • 3 Types • Beta-pleated sheet • Polypeptide chains held together side by side by hydrogen bonds between the peptide chains • Stacks of chains

  14. Secondary Proteins • Three types • Triple helix – ex. Collagen • Three polypeptides woven like a braid

  15. Collagen • Most abundant protein (1/3 of all protein in vertebrates) • Found in connective tissue, blood vessels, skin, tendons, ligaments, cornea of the eye, cartilage • Very strong due to its structure • Deficiency in vitamin C weakens collagen because it breaks down the hydrogen bonding between the fibers • Causes brittle bones, cartilage, and tendons and wrinkles in the skin

  16. Tertiary Proteins • Involves attractions and repulsions between the side chain groups of the amino acids in the polypeptide chain, causing bending and twisting into a 3D shape

  17. Types of Interactions in Tertiary Structures • Hydrophobic interactions: attractions between nonpolar groups • Hydrophilic interactions: attractions between polar or ionized groups • Salt bridges: between ionized acidic and basic amino acids • Hydrogen bonds: between H and O or N • Disulfide bonds: covalent links between sulfur atoms

  18. Globular Proteins • Have compact, spherical shapes • Sections of the polypeptide chain fold over on top of one another • Functions of globular proteins: synthesis, transport, metabolism

  19. Myoglobin • Example of a globular protein is myoglobin • Stores oxygen in skeletal muslce • Especially common in sea mammals such as seals and whales, which allow them to stay under the water for long periods of time

  20. Fibrous Proteins • Long, thin, fiber-like shapes • Function: structure of cells and tissues • Example: keratin • Found in hair, wool, skin and nails

  21. Quaternary Proteins • Two or more polypeptide subunits • Example: hemoglobin • Function: transports oxygen in blood • Consists of four polypeptide chains; two α and two β chains, held also by one of the 5 bonds in tertiary structures • The structure allows hemoglobin to carry 4 oxygen molecules at the same time

  22. Hemoglobin

  23. Denaturation of Proteins • Denaturation occurs when there is a disruption of the bonds that stabilize the secondary, tertiary or quaternary structure • Does not affect the covalent amide bonds of the primary structure

  24. Examples of Denaturation • Heating • Cooking food/autoclaving surgical supplies • Acids/Bases • Lactic acid denatures milk proteins to make yogurt and cheese • Organic Compounds • Alcohol disinfects wounds • Heavy Metals • Causes mercury and lead poisoning • Agitation • Using egg whites to make whipped cream/meringue

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