Functional Diversity of Proteins

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Functional Diversity of Proteins

• Catalysis Enzymes amylase, pepsin, lipase

• Transport hemoglobin, serum albumin

• Structure keratin, collagen

• Movement, Contraction myosin, actin

• Defense antibodies, fibrinogen

• Nutrient and Storage egg albumin, zein

• Regulation hormones (insulin), repressors

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Protein Classification by Function
Structure
Transport
Regulation
Motion
Catalysis
Regulation
Catalysis
Defense
Missing Function?
Storage
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Classification of Proteins
By Shape
Fibrous -insoluble in water Functions
structure, motion High percentage of nonpolar
amino acids
Globular -usually soluble in water Functions
transport, catalysis, storage Higher percentage
of polar and charged amino acids
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Classification of Proteins
By Composition
Simple contain only amino acids Examples
amylase, pepsin
Conjugated - contain something besides
amino acids Examples
Hemoglobin - contains iron Immunoglobin -
contains carbohydrate Lactate
dehydrogenase - contains niacin
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Nonpolar Amino Acids
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Polar, Uncharged Amino Acids
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Polar, Charged Amino Acids
Negatively-charged
Positively-charged
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Amino Acid Classification Functional Group
Sulfhydryl
Alcohol
Carboxylic Acid
Amide
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?-carboxyl group
?-carbon
side chain
?-amino group
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Amino Acid Titration
Below Isoelectric pH Net Charge
Above Isoelectric pH Net Charge
Isoelectric pH Net Charge 0
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Titration of Glycine
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Titration of Glutamic Acid
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Titration of Histidine
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Electrophoresis of Amino Acid Mixture at pH
6 Alanine, Arginine, Aspartic Acid
At pH 6
Alanine (pI 6)
Net charge 0
Arginine (pI 10.8)
Net charge is
Net charge is
Aspartic Acid (pI 2.8)
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Paper Chromatography of Amino Acids
Tyr
Phe
Leu
Gly
Asp
Lys
polar amino acids
nonpolar amino acids
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Biologically Active Peptides
Impact of changes in amino acids
Vasopressin - Stimulates water reabsorption in
the kidney
Oxytocin - Stimulates lactation and uterine
contraction
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Levels of Protein Structure
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Forces Involved in Protein Structure
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Primary Structure of Insulin
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Primary Structure of Lysozyme
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Secondary Structure
?-Helix
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Secondary Structure
?-Structure
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Collagen (triple helix)
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Elastin Structure
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Myoglobin Secondary and Tertiary Structure
??- helix
??- helix
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Myoglobin
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Lysozyme Secondary and Tertiary Structure
??- helix
??- structure
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Lysozyme Tertiary Structure
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Hemoglobin Quaternary Structure
Heme Group
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Sickle-cell Hemoglobin
valine-valine interaction
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Electrophoresis of Hemoglobin A, Sickle-Cell
Hemoglobin, and Hemoglobin C
Hemoglobin S Glu to Val at Position 6 on the
Beta Chain
Hemoglobin C Glu to Lys at Position 6 on the
Beta Chain
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Protein Denaturation

• Denaturation involves
• The disruption of bonds in the secondary,
  tertiary and quaternary protein structures.
• Heat and organic compounds that break apart H
  bonds and disrupt hydrophobic interactions.
• Acids and bases that break H bonds between polar
  R groups and disrupt ionic bonds.
• Heavy metal ions that react with S-S bonds to
  form solids.
• Agitation such as whipping that stretches peptide
  chains until bonds break.

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Applications of Denaturation

• Use of 70 ethanol or isopropyl alcohol as a
  disinfectant

• Use of silver nitrate solution in eyes of
  newborns to
• prevent gonorrhea infection

• Use of eggs or milk as antidote for heavy metal
  poisoning

• Use of tannic acid in burn ointment to coagulate
  proteins
• at burn site

• Use of high temperature to sterilize items

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Denaturation and Renaturation of Ribonuclease