Protein

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Protein

• 1. Large molecules, 103 to 108amu
• 2. Polymers of amino acids in specific sequences
• 3. Sequence determines function
• 4. Homo sapiens, 20 different amino acids make up
  all proteins

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Protein Types

• 1. Structural- provide structure
• a. Collagen- tendons cartilage
• b. Keratin- hair, skin, wool, nails
• c. Spongin- sponges, Porifera
• 2. Contractile- movement, muscles filaments
• a. Myosin- contractile ms filament
• b. Actin- anchor ms filament

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Protein Types

• 3. Transport- carry substances in body
• a. Hemoglobin hemocyan- transport O2
• b. Lipoproteins- transport lipids
• 4. Storage- store nutrients
• a. Casein- stores protein in milk
• b. Albumin- stores protein in eggs blood
• c. Ferritin-stores iron in spleen liver

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Protein Types

• 5. Hormone- regulate metabolism nervous system
• a. Insulin- regulates blood glucose levels
• b. Somatropin- growth hormone, regulates growth
  phases

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Protein Types

• 6. Enzyme- catalyse biochem rxn
• a. Sucrase- hydrolysis of sucrose
• b. Trypsin- hydrolysis of proteins
• 7. Protection- defense of organism
• a. Immunoglobulins- stimulate immune response
• b. Venoms- poisons to kill, stun, or discourage
  attackers

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Amino Acids

• 1. H atom, amino group, carboxyl group,
  functional group attached to central carbon, aC
• 2. Different functional groups determine
  characteristics of individual amino acids
• 3. Nonpolar aa, polar aa, acidic aa, basic aa

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Amino Acid Structure

• amino
  carboxyl
• group
  group
• functional
• group

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Nonpolar Amino Acids

• 1. Hydrophobic aromatic group or hydrocarbon
  chain
• 2. Glycine, alanine, valine, isoleucine, leucine,
  methionine, phenylalanine, proline, tryptophan

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Polar Amino Acids

• 1. Hydrophilic functional groups
• 2. Serine, threonine, asparagine, cysteine,
  tyrosine, glutamine

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Acidic Amino Acids

• 1. Carboxylic acid on functional group
• 2. Aspartic acid, glutamic acid

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Basic Amino Acids

• 1. Amine group on functional group
• 2. Lysine, arginine, histidine

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Essential Amino Acids

• 1. Ten aa are essential, must be in diet
• 2. Essential- arg, his, ile, leu, lys, met, phe,
  thr, trp, val
• 3. Ten aa can be synthesized from essentials
• 4. Nonessential- ala, asn, asp, cys, gln, glu,
  gly, pro, ser, tyr

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Dipolar Ion

• 1. Dipolar ion- carboxyl grp donates H and amino
  grp accepts H
• alanine,
• dipolar ion

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Amino Acid Ionization

• 1. Most aa exist as dipolar ions, net charge 0
• 2. In acid soln, carboxyl grp accepts H aa
  has positive charge
• 3. In basic soln, amino grp donates H aa has
  negative charge

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Peptide bond

• 1. Amide bond between carboxyl grp of one aa
  amino grp of another
• 2. Small peptides named starting at amino group
  using -yl or 3 letter abbreviations

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Tripeptide

• alanylglycylserine or ala-gly-ser, a tripeptide

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Aspartame

• L-aspartic acid methylesterphenylalanine

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Polypeptide

• 1. Long chains of amino acids
• 2. Protein- gt50 amino acids
• 3. Primary, secondary, tertiary, quaternary
  structure

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Primary Structure, 1o

• 1. Sequence of amino acids in protein, 1o
  sequence determines function
• 2. Thyroxine Releasing Hormone- glu-his-pro
  sequence
• 3. Insulin- two chains, 21 aa in a chain 30 aa
  in b chain

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Secondary Structure

• 1. Alpha helix
• 2. Beta sheet
• 3. Triple helix

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Alpha Helix

• 1. Hydrogen bonds between amino groups carbonyl
  groups twist amino acid chain into a helix or
  spiral
• 2. Functional groups are outside

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Beta Sheet

• 1. Hydrogen bonds between amino groups carbonyl
  groups fold parallel amino acid chains into
  pleated sheet
• 2. Functional groups are on opposite sides of
  sheet

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Triple Helix

• 1. Three amino acid chains woven into a braid
• 2. Structure of collagen, found in connective
  tissue, skin, tendons, ligaments

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Tertiary

• 1. Three dimensional shape of protein
• 2. Attractions repulsions from side groups fold
  protein into specific shape
• 3. Globular proteins- compact roughly
  spherical, polar
• 4. Fibrous proteins- long thin fibers,
  structural

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Quaternary

• 1. Two or more polypeptide units held together by
  side group interaction
• 2. Hemoglobin- globular, two a chains two b
  chains

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Protein Denaturation

• 1. Bonds that stabilize the 2o, 3o, or 4o
  structure weakened or broken
• 2. Heat, acids, bases, certain organic compounds,
  heavy metal ions, agitation

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Enzymes

• 1. Protein catalysts that lower activation energy
  rxn rate of cellular chemical reactions
  required for metabolism
• 2. Pepsin, trypsine, sucrase, lipases, carbonic
  anhydrase

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Enzyme Specificity

• 1. Absolute- one type of rxn for one substrate,
  urease hydrolysis of urea
• 2. Group- one type of rxn for substrates with
  same functional, hexokinase addition of PO4-3
  to sugars
• 3. Linkage- one type of rxn for particular bond,
  lipase hydrolysis of glycerol fatty acids

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Enzyme Rxn Process

• 1. Substrate attaches to active site of enzyme,
  enzyme-substrate complex
• 2. Substrate converted to product at active site,
  enzyme-product complex
• 3. Product released from active site
• 4. Lock key model induced fit model

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Enzyme Structure

• 1. Simple enzyme- only peptides
• 2. Complex enzyme
• a. Apoenzyme- protein part
• b. Cofactor- nonprotein part, usually a metal
  ion Cu2, Fe2, Mg2, Mn2, Zn2
• c. Coenzyme- required by some enzymes, vitamins

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Enzyme Activity

• 1. Substrate concentration- proportional to
  point, positive logarithmic function
• 2. Temperature- proportional to point, Topt
  37oC, gt37oC denatures enzyme
• 3. Acid-base balance- above or below pHopt
  ionizes side groups, changes reactivity

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Enzyme Inhibition

• 1. Inhibitors- combine with enzyme, rxn rate,
  some antibiotics inhibit bacterial enzymes
• 2. Competitive- inhibitor structure similar to
  substrate, occupies active site blocking enzyme
• 3. Noncompetitive- inhibitor bonds to enzyme
  changes structure of active site, Pb2, Ag,
  Hg2, reversible irreversible

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