1A.6-1A.8 Enzymes

• How does pH affect enzyme activity?

  pH alters ionic and hydrogen bonds when it is either too low or too high, this changes the secondary and tertiary structure of the enzyme therefore changing its active site so its no longer complimentary to the substrate.
• what is an anabolic enzyme?

  an enzyme that catalyses the build up of molecules?
• are enzymes specific? what does that mean?

  yes, they only catalyse certain reactions as enzyme active sites are complimentary to substrates.
• How does temperature affect enzyme activity?

  as temperature increases enzymes have more kinetic energy so frequency of successful collisions increase. after optimum temp (40 degrees) activity begins to decrease as hydrogen bonds break and enzymes denature/ lose specificity.
• what two functional groups are either side of an enzyme?

  amine (NH2) and hydroxyl (OH).
• what is an intercellular enzyme?

  an enzyme that catalyses reactions inside the cell.
• how do anabolic enzymes lower activation energies?

  when two substrate molecules enter the active site, the enzyme hold them together, reducing repulsion so they can bond more easily.
• what is a catalyst?

  something that speeds chemical reactions by offering a path of lower activation energy without being used up.
• what is an extracellular enzyme ?

  an enzyme that is secreted by cells and catalyses reactions outside the cell.
• what is an enzyme?

  a globular protein that acts as a biological catalyst for metabolic reactions.
• what is optimum temperature for enzymes?

  40 degrees.
• what is a metabolic pathway?

  series of chemical reactions in which the product of one reaction is the substrate for the next reaction.
• what is a catabolic enzyme?

  and enzyme that catalyses the break down of molecules.
• what is metabolism?

  sum of all chemical reactions in the body.
• how do catabolic enzymes lower activation energies?

  when the substrate enters the active site it puts a strain on the bond so it breaks more easily.
• why is the bodies temperature not naturally 40 degrees if that is optimum for enzyme activity?

  it allows the body to fluctuate temperature (increase a few degrees) without affecting enzyme activity.
• what happens to the amount of product produced in the presence of of non competitive inhibitors?

  less product is formed as the change in shape of the active site is mostly irreversible.
• what is a non competitive inhibitor?

  a molecule that binds to an enzyme (not the active site) causing it to change its tertiary shape which changes the shape of the active site so it is no longer complimentary.
• what are the two types of inhibitors?

  competitive and non-competitive.
• how does the concentration of substrates affect enzyme activity?

  if more substrate molecules are available rate rate of reaction will increase as there will be more successful collisions.once there is more substrates than enzymes, rate will not further increase.
• what is an inhibitor?

  molecules that stop/reduce enzyme activity.
• what is a competitive inhibitor?

  an inhibitor that is a similar shape to substrate so binds to the active site of the enzyme preventing enzyme substrate complexes to form.
• how does enzyme concentration affect enzyme activity?

  the more enzymes present, the higher the rate of reactions as there are more enzymes to catalyse reactions.
• what is the optimum pH for enzymes?

  7/8.
• what happens to the amount of product produced in the presence of competitive inhibitors?

  same amount of product produced, just reached at a slower rate.
• What are the two enzyme models?

  lock and key, induced fit model
• What is the lock and key model?

  Enzymes are specific to the substrate they bind too, their active site is fixed and cannot change shape.
• What is the induced fit model?

  The enzymes active site is not perfectly complimentary to the substrate so the active site undergoes conformational change (molds) to fit the substrate and form a complex.
• How can you measure the rate of an enzyme controlled reaction?

  how fast the product of the reaction appears

  or

  the disappearance of the substrate
• What 3 aspects need to be considered when choosing a temperature for an experiment?

  that there will be sufficient kinetic energy

  it is not too high to denature proteins

  it is close to the optimum
• how can the difference in primary structure of proteins provide evidence for evolution?

  mutations occur over time which change the base sequence of the nucleotides.

  this causes a change in the amino acid sequence.

  closely related species will have little difference in their primary structure but the larger the difference the more mutations will occur.
• How would you stop a reaction measuring enzyme activity?

  Boil or add either a strong acid or alkali

  to denature the enzyme
• Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end.

  amine group ionically bonds to the carboxyl group to form a peptide bond which leaves one of each group free at opposite ends
• how are all dipeptides similar?

  contain 2 R groups

  contain H,C,N,O
• how do all dipeptides differ?

  varying R groups
• The secondary structure of a polypeptide is produced by bonds between amino acids.

  Describe how.

  Hydrogen bonds form between amine and carboxyl group which cause the polypeptide to form either an alpha helix or beta pleated sheet
• Two proteins have the same number and type of amino acids but different tertiary structures.

  Explain why.

  they could have a different sequence of amino acids which would result in the hydrogen bonds forming in different orientations
• what do non competing inhibitors alter in enzymes?

  their tertiary structure which in turn changes their shape of the active site
• what is the general structure of an amino acid?

  NH2CHRCOOH