Enzymes

• what is the role of enzymes?

  to cataylse metabolic reactions.
• what are enzymes?


  biological catalysts.
• what category is enzyme under?

  protein.
• what can enzymes affect?

  they can affect structures in the organism (enzymes help to produce collagen) and functions (respiration).
• what can enzyme action be?

  intracellular or extracellular
• what does intracellular mean?

  inside the cell
• what does extracellular mean?

  outside the cell
• what do enzymes have that allow them to be bound to?

  an active site which has a specific shape.
• what is the active site?

  the part of the enzyme where the substrate molecules bind to.
• what is a substrate molecule?

  the substance that the enzymes interacts with.
• what causes enzymes to be highly specific?

  their tertiary structure.
• what is activation energy?


  energy needed to start a chemical reaction.
• how do enzymes affect activation energy?

  they lower the amount of activation energy that's needed often making reactions happen at a lower temperature which speeds up the rate of reaction.
• what forms when a substrate fits into the enzyme's active site?

  an enzyme-substrate complex.
• what are the 2 reasons why the enzyme-substrate complex lowers the activation energy?

  1) if 2 substrate molecules need to be joined then being attached to the enzyme holds them closer together reducing any repulsion between the molecules so they can bond easier.

  2) if the enzyme is catalysing a breakdown reaction then fitting into the active site puts a strain on bonds in the substrate so the substrate molecule breaks up easier.
• what model did early scientists come up with?

  the lock and key model.
• what is a simple explanation of the lock and key model?

  the substrate fits into the enzyme in the same way that a key fits into a lock.
• what was wrong about the lock and key model?

  the enzyme-substrate complex needs to change shape slightly to complete the fit.
• what was the new model for enzyme action?

  the induced fit model.
• what does the induced fit model help to explain?

  why enzymes are so specific and only bond to one particular substrate.
• the substrate doesnt only have to be the right shape to fit the active site...


  it also has to make the active site change shape in the right way as well.
• what is the induced fit model a prime example of?

  how a widely accepted theory can change when new evidence comes along.
• how specific are enzymes and how many reactions do they normally catalyse? eg?


  enzymes are very specific and normally only catalyse one reaction. eg: maltase only breaks down maltose.
• why are enzymes so specific?

  bc only one complimentary substrate will fit into the active site.
• what determines the active site's shape?

  the enzyme's tertiary structure.
• what determines the tertiary structure?


  the primary structure.
• each different enzymes has a different..? so?

  tertiary structure so a differently shaped active site.
• what happens if the substrate doesnt match the active site?

  an enzyme-substrate complex wont be formed and the reaction wont be catalysed.
• what happens if the tertiary structure of the enzyme is altered?

  the shape of the active site will be changed so the substrate wont fit into the active site so an enzyme-substrate complex wont be formed and the enzyme wont be able to carry out its function.
• what could alter the tertiary structure?

  changes in pH or temperature.
• what determines the primary structure?

  a gene.
• what could happen if a mutation happens in the gene of the primary structure ?

  it could change the tertiary structure of the enzyme produced.
• what increases when the temperature increases?

  the rate of an enzyme-controlled reaction.
• why does rate of enzyme-controlled reaction increase when temperature does?

  because more heat means more kinetic energy so molecules move faster so the enzymes are more likely to collide with the substrate molecules and the energy of the collisions increase so each collision is more likely to result in a reaction.
• what would happen if the temperature gets too high?

  the reaction stops.
• Each enzymes has an optimal

  an optimum temperature and optimal pH value.
• describe how temperature and enzymes relate

  1) the rise in temperature makes the enzymes molecules vibrate more.

  2) if the temperature goes above a certain level, this vibration breaks some of the bonds that hold the enzyme in shape.

  3) the active site changes shape and the enzyme and substrate no longer fit together.

  4) at this point, the enzyme is denatured and so no longer functions as a catalyst.
• what, aside from temperature, affects enzyme activity?

  pH.
• what optimal pH value do most human enzymes work best at? but?

  pH 7 but there are exceptions.
• what is an example of a human enzyme that doesnt work best at pH 7?

  eg: pepsin works best at acidic pH 2.