Exam q proteins

• Explain why changing one amino acid in a primary structure may result in a different tertiary structure

  • Changing one amino acid changes the amino acid sequence
  • different amino acids Hve different r groups
  • so bonds form in different places
  • different folding into a 3D shape occurs
• Decreasing pH affect enzyme activity

  • decreases enzyme activity
  • Decrease of pH means increase in hydrogen ions Attracted to amino acids
  • Disrupts ionic and hydrogen bonding so tertiary structure changes
  • So Active site change shape
• Explain why the graph flattens out 


  Because

  • Flattens out at saturation point
  • All active sites are full so adding more substrate won’t increase the reaction any further
• Competitive inhibitor exam a structure

  example

  • c.i has similar shape as substrate
  • So it acts as a competitive inhibitor , binding to the enzymes active site preventing substrate from binding
  • Lower levels of product formed
• Describe how a peptide bond I formed between two amino acids forming a di peptide

  • Condensation reaction or loss of water
  • Between amine group and carboxyl
• Control variables for experiments using enzymes

  • pH
  • Temperature
  • Initial substrate concentration
  • Volume of substrate solution
  • Enzyme concentration
• Describe how a non competitive inhibitor can reduce the rate of enzyme controlled reaction

  • Binds to allosteric site
  • Active site changes shape
  • No longer complementary
  • Therefore enzyme and substrate can’t bind
  • Enzyme substrate complex can’t form
• Explaining from a graph why it’s non competitive (1)

  • Increasing substrate concentration doesn’t increase enzyme activity / rate of reaction (mp1/2)
  • High substrate concentration doesn’t overcome inhibition

  
• Explain the difference in initial rate of reaction at 60 and 37 degrees

  • More kinetic energy
  • More enzyme substrate complex form
• Why is it more efficient to use immobilise enzymes?

  • Enzymes can be reused
  • Enzymes won’t contaminate the final product
  • It allows for a continuous process
  • It offers enzyme stability
• What’s meant by the term catalyst

  • A substance that speeds up a reaction
  • Without being used up In the reaction
• What’s meant by activation energy do an enzyme and how does the presence of an enzyme affect It

  • A.E is the minimum amount of energy needed for a reaction to start
  • Enzyme lowers the activation energy
• Why is the tertiary structure of an enzyme essential to its function

  • Tertiary structure determines shape of active site
  • Active site only complimentary to specific substrate
  • Any change in shape will mean an enzyme cant Catalyse that reaction
• Why is the induced fit model considered to be a better theory than lock and key model

  • Enzymes are not rigid structures
  • substrate binds to the active site
  • The active site of an enzyme changes shape slightly to become fully complementary
  • Ensures tighter bonding in active site that puts a strain on bonds and lowers the activation energy needed to break the bonds in the substrate
• Name the type of peptidase which will hydrolyse a peptide bond

  • Endo peptidase
• Describe how a quaternary protein is formed from its monomers (5)

  • Primary structure is the specific sequence of amino acid that are joined by peptide bonds
  • Joined with condensation reactions
  • Secondary structure is formed via hydrogen bonds / involves formation of alpha helix and beta pleated sheet
  • Tertiary structure is held by hydrogen bonds , ionic and disulphide bonds between the R groups
  • Quaternary structure - more than one polypeptide chain
• Describe how monomers join to form the primary structure of a protein

  • Monomers (Amino acid ) join together in condensation reactions
  • Forming peptide bonds
  • Making a specific sequence of amino acids
• In the control experiment cooked wheat was chopped up to copy the effect of chewing suggest a more appropriate control experiment and explain your suggestion

  • Add boiled saliva
  • Everything will be the same as the experiment but salivary amylase will be denatured
• Explain why enzyme Maltase only breaks down maltose and allows for this reaction to take place at normal body temperature 


  M

  • Tertiary structure / 3D shape of an enzyme means
  • Active site is complementary to the substrate
  • They fit by induced fit
  • lowering the activation energy
  • By forming enzyme substrate complex Which places a strain on the bonds
• Describe the structure of proteins

  1. Polymer of amino acids
  2. Joined by peptide bonds
  3. Formed by condensation reactions
  4. Primary structure is specific order of amino acids
  5. Secondary structure is folding of polypeptide chain due to hydrogen bonding
  6. Tertiary structure is 3D folding due to hydrogen bonding and ionic and disulphide
  7. Quaternary is two or more polypeptide chains
• Describe how proteins are digested in human gut

  1. Hydrolysis of peptide bonds occur
  2. Endopeptidases breaks polypeptide chains into smaller chains
  3. Exopeptidases remove terminal amino acids
  4. Dipeptidases hydrolyses dipeptides into amino acids
• Describe how the structure of proteins depend on the amino acids it contains

  • Structures determined by the R group interactions
  • primary structure is the specific order of amino acids
  • Secondary structure is formed by hydrogen bonding between amino acids forme alpha helix
  • Tertiary structure is formed by interaction between r groups
  • Creates the active sites in enzymes
  • Quaternary structure contains two or more polypeptide chains
• Enzymes catalyse only one reaction explain why

  1. Active site has a specific shape
  2. Allows binding of only one substrate to form an enzyme substrate Complex
• Explain why amylase produced in the human digestive system doesn’t digest GOS (2)

  1. Active site is only complementary to its own substrate / active sites not complementary to GOS
  2. Due to tertiary structure of enzyme
• Student repeated the experiment with a higher concentration of lipase solution describe and explain the results you would expect him to get (3)

  1. faster fall in ph and levels of at same point
  2. More enzyme complex forms
  3. Same amount of fatty acids are produced