Proteins

• 3 prion diseases

  1. Scrapie in sheep2. Bovine Spongiform encephalopathy (BSE)..mad cow disease.3. Variant Creutzfeldt-Jakob disease (vCJD)...human BSE, can get this if eat contaminated beef.

  
• 3 ways disease causing prions arise

  1. Normal prions sponatneously change into disease causing prions.2. DNA that codes for the prion mutates.3. Eating food that contains disease causing prions.

  
• 2 Features of disease causing prions

  1. Can replicate2. Are infectious
• When prion levels go above the threshold?

  Neurogenerative disorders in brain arise that lead to death.
• What happens when a disease causing prion enters the body?

  It acts as a template causing normal prions to convert to the disease causing form.
• Forms of Prion

  Normal PrPDisease Causing form PrPsc (far more beta pleated sheets)

  
• Prions

  Protein found in the nervous system of mammals and are important for the transmission of impulses in the nervous system across the synapse.

  
• Globular Proteins


  Have a very specific 3 D shape.Have metabolic roles e.g enzymesHaemoglobin

  
• Collagen

  1. Fibrous protein2. 3 polypeptides wound round each other held by Hydrogen bonds.3. Found in tendons that link muscle to bone.

  
• Fibrous Proteins

  Polypeptides are in strands/sheets.Chains are linked by cross-bridges so are very strong and stable.Important for structure e.g Collagen

  
• 2 Main protein groups

  1. Fibrous2. Globular
• Haemoglobin Structure

  Conjugated protein.4 Polypeptide chains.Each chain is attached to an iron rich haem group.

  
• Conjugated proteins

  Quaternary proteins that contain a non-protein prosthetic group e.g glycoprotein and haemoglobin.

  
• Quaternary Structure

  A protein made of two or more polypeptide chains bonded together.

  
• 4 Bonds in a Tertiary Structure

  1. Hydrogen2. Ionic Bonds3. Disulfide Bonds...between S in the R groups4. Hydrophobic Interactions (between hydrophobic R groups)

  
• Tertiary Structure

  When the secondary structure is folded further to give the protein a unique 3D shape.Bonds form between the R groups to create the unique shapes.

  
• Secondary structure

  The simple folding of the polypeptide chains into either an a-helix or a B-pleated sheet held by Hydrogen bonds.

  
• Primary structure

  The number and sequence of amino acids in a polypeptide chain.

  
• Polypeptide


  Many amino acids joined in a chain.

  
• Dipeptide

  2 amino acids joined together.

  
• How are amino acids joined together?

  Joined by peptide bonds through condensation reactions.Condensation reaction takes place between the amino group of one amino acid and the carboxyl group of another.

  
• Draw an amino acid.

  
• What makes the 20 amino acids different?

  Each different amino acid has a different R group.If sulfur is present it is in the R group.
• Why is the sequence of amino acids in a protein important?

  Sequence determines the shape and therefore the function of a protein.
• How many different types of amino acid are there?

  20
• Why are proteins polymers?


  Long chains of amino acids.
• What elements do proteins contain?

  Carbon, Hydrogen, Oxygen, Nitrogen and often Sulfur.