Proteins

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Proteins

• The most diverse molecules in living organisms!

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• Proteins have 2 main roles
• Structural building blocks (ex spider web)
• Functional molecules (ex enzymes)

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Examples of proteins

• Functional
• Enzymes biological catalysts
• Immunoglobulins protect animals from foreign
  microbes and cancer cells (antobodies)
• Hemoglobin shuttles oxygen
• Structural
• Keratin tough structures in hair, fingernails
• Fibrin helps clot blood
• Collagen forms protein component of bones, skin,
  ligaments and tendons

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What are they made of?

• Amino acids (a.a.) are the subunits

R group side chain
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A bit about the amino acids

• There are 20 a.a.s (p42 43)
• 8-10 are essential because our body cannot
  synthesize them so we need to get them from our
  diet.

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The amino acids
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No you dont have to memorize them maybe in
university though
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How are proteins made?

• DNA directs ribosomes, RNA and enzymes to join
  a.a.s together in the correct sequence (this is
  called protein synthesis)
• The aas are joined together by peptide bonds
  (aka amide bond)
• Resulting polymer is called a polypeptide

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Polypeptides are formed by condensation reaction
between the amino group of one amino acid and the
carboxyl group of the adjacent amino acid
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Two general categories of proteins

• Polypeptide a few aa in length to gt1000.
  Usually linear strands or sheets
• AND
• Globular are made of 1 or more polypeptide
  chains in a rounded, spherical shape (ex
  enzymes)

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• The final shape (conformation) of a protein is
  determined by a.a. sequence and can be
• Primary straight chain of a.a (ex insulin)
• Secondary The a.a. chain coils and folds making
  helices and pleated sheets (ex keratin, spider
  silk)
• Tertiary A secondary protein undergoes more
  folding due to environmental forces. This can be
  done by a chaperone protein. Is now globular.
• Quarternary 2 or more polypeptides come together
  to make one functional protein (ex keratin,
  collagen, hemoglobin). Is also globular.

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Denaturation

• Chemical and physical environmental factors
  (temperature, pH, ionic concentration) can cause
  proteins to change shape (denature) and lose
  their function.
• Denaturation can be
• Dangerous example- prolonged fever above 39
  celcius can denature critical enzymes in the
  brain.
• Useful blanching of fruit, straightening hair,
  cooking meat to make it easier to chew

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