Proteins

• what are the monomers from which proteins are made?


  Amino acids
• What is the general structure of an amino acid?


  . 20 amino acids exist. R group= variable group, NH2= amine group, cooh = carboxyl group

  
• What is formed between a condensation reaction of 2 amino acids?

  peptide bond.
• How are dipeptidases formed?

  condensation reaction between 2 amino acids.
• How are polypeptides formed?

  Condensation reaction of many amino acids
• what is the primary structure?


  The order of amino acids in the polypeptide chain
• What is the secondary structure?


  The sequence of amino acids that cause parts of a protein molecule to bend into alpha helix or beta pleated sheet held by ‘H’ bonds between c- - o groups of carboxyl group of an amino acid and ‘H’ in amine group of another amino acid
• What is the tertiary structure?

  1. further folding of secondary structure
  2. forms unique 3D shape
  3. held by hydrogen and disulphide bonds
• Where do ionic and disulphide form?


  Between R groups of different amino acids

  disulphide only occurs sometimes bc needs to be one sulfur in R group so it occurs
• What is quaternary structure?


  a protein made up of more than one polypeptide chain

  e.g haemoglobin
• Why is a protein denatured?


  Bonds that hold the tertiary and secondary structure in shape break and loses unique 3D structure
• What are conditions that denatures a protein?

  1. Too high temp
  2. too high/too low a pH
• What might cause a change to amino acid sequence?

  mutations
• What is the biochemical test for proteins?

  1. Add biruet
  2. add protein sample
  3. blue to lilac ( protein is present)
• What does an enzyme do when catalysing a reaction?


  Lowers the activation energy
• what part of an enzyme attaches to the substrate to catalyse a reaction?


  active site
• Why is the active site special and unique in shape?


  specific folded and bonding in tertiary structure of the protein SO active sites attach to complementary substrates
• what does the induced fit model suggest? 


  Active site is not exactly complementary to substrate when substrate collides with enzyme, active site

  SLIGHTLY changes to fit around the substrate and form an E-S complex
• What happens to the activation energy when active site slightly changes?

  Decreases, bonds weaken due to strain
• What affect does low temp have on enzymes? 


  if temp is too low: not enough collisions between enzyme & substrate
• What affect does high temp have on enzymes?

  -Denature of enzyme

  -active site changes shape, ES complex can’t be formed

  -bonds broken for tertiary structure
• What affect does too high or Too low pH have on enzymes?


  Interfere with charges in amino acids in active site

  breaks bonds holding tertiary structure

  change Active site shape

  denature of enzyme= less ES complexes made
• What affect does insufficient substrate have?

  -slower reaction -fewer collisions between enzyme& substrate
• What affect does insufficient enzymes have?


  Active sites become saturated and unable to work any faster
• What is a competitive inhibitor? 


  Same shape as substrate and binds to active site, prevents substrate from biding and reaction occurring
• What Will happen to the inhibitor if you add more substrate?


  flood out/ out compete the inhibitor and knock them out of active site
• What is a non- competitive inhibitor?


  binds away from biding site, causes active site to change shape so substrate can no longer bind regardless of amount of substrate added
• What is the method of investigation on pH on trypsin (enzyme) PT1

  1.use forceps to place a piece of film in the into slit cut into straw

  2.use syringe to measure 4cm3 of trypsin in test tube

  3.use a different syringe to measure 4cm3 of pH4 buffer sol. Place in same test tube

  4.place test tube in beaker of water at 37 degrees (use thermometer) wait for all contents to reach 37 degrees C
• What is the method of investigation pH on trypsin (enzyme) PT2

  5.once at temp, place straw attach with film attached into solution & immediately start stop clock

  6.dunk strays &down every 10 seconds

  7. when film is completely clear=reaction finished. Compare film to already cleared film to decide endpoint. Record time it took. If no change after 25 Mins= no reaction

  8. repeat for all pH values

  (repeat with water to control experiment)
• Why is it better to plot in standard form on your graph?

  Because it’s easier to plot
• When should you join lines dot to dot with a ruler?


  When you don’t have enough data points to accurately predict the pattern
• When should you draw a curve/straight line of best fit?

  When you have enough data points to accurately predict the pattern
• What are method limitations?

  1.end point is subjects which leads to inaccurate time taken measurements

  2.the water bath not thermostatically controlled- temp decrease during practical

  3.not enough intermediate pH values tested to accurately identify optimum pH

  4.range of pH not wide enough as denature point not identified