Proteins

• Primary

  The specific sequence of amino acids in a polypeptide chain joined by peptide bonds
• Secondary

  The curling or folding of the polypeptide chain into alpha helices and beta pleated sheets due to the formation of hydrogen bonds
• Tertiary

  The overall specific 3D shape of a protein which is determined by interactions between R groups and the properties of R groups

  Hydrogen bonds, Ionic bonds and disulphide bridges
• Quaternary

  Multiple polypeptide chains bonded together
• Number of naturally occurring amino acids

  20
• Dipeptide formation

  Two amino acids joined together by a condensation reaction - forms a peptide bond between them
• Polypeptide

  A polymer made up of many amino acids joined together by a condensation reaction which forms peptide bonds between them
• Amino group

  -NH2
• Carboxyl group

  -COOH
• Draw the general structure of amino acids


  ...
• Describe how to test for proteins in a sample

  Biuret test

  Add equal volumes of NaOH to sample at room temp.

  Add drops of dilute copper (ii) sulfate solutions

  Swirl to mix

  Positive = blue to purple
• How do amino acids differ?

  By their side R group
• Polypeptide?

  3 or more amino acids
• Dipeptide?

  2 amino acids
• Describe the structure and function of globular proteins?

  Spherical and compact

  Hydrophilic R group faces outward

  Hydrophobic R group faces inwards = water soluble

  Involved in metabolic process (haemoglobin and enzymes)
• Describe the structure and function of fibrous proteins?

  Structure: Long chains or fibres which are insoluble in water

  Function: Fibrous proteins provide structural support and strength to cells and tissues. They often form fibres or sheets, and are found in structures such as hair(collagen),nails, tendons
• Outline how chromatography could be used to identify amino acids in a mixture?

  Use capillary tube to spot mixture onto pencil origin line

  Place paper in solvent

  Allow solvent to run until it's almost at the top

  Amino acids move different distanced based on attraction to the paper and solubility in solvent

  Use revealing agent or UV light to see spots

  calculate Rf value