Topic 1.4 Enzymes Flashcards
Affects the rate of collisions
-Temperature (kinetic energy)
-Substrate concentration
-Enzyme concentration
-Inhibitors (competitive)
Affects the active site
-Temperature (denaturation)
-pH (denaturation)
-Inhibitors (non-competitive)
Competitive inhibitors
-Similar shape to substrate
-Binds to active site of enzyme
-Affects collision rate
Non-competitive inhibitors
-Binds to the enzyme (not active site) and changes the shape of the active site
-Binds to allosteric site
-Substrate no longer fits
-Affects active site
How enzymes affect activation energy
Enzymes are catalysts because they lower the activation energy needed to drive a reaction.
Induced fit model
States a substrate binds to an active site and both change shape slightly, creating an ideal fit.
Rate equation
Rate= change/time
Trypsin investingation variables
Milk —> amino acids (trypsin used)
-Regulate the temperature using a water
-Keep concentration of trypsin the same
-Keep the intervals regular (5° each time-then add intervals to find the optimum)
-Regulate the repeats (3 repeats for each)
Investigating enzymes: Catalyse
Hydrogen peroxide —> water + oxygen (catalyse used)
-Add catalyse to hydrogens peroxide
-Use a gas syringe to collect the oxygen
-Serial dilution of the stock solution
-Repeats to find outliers and a mean
Investigating enzymes: Amylase
Starch —> maltose (amylase used)
-Add buffer solution to enzymes (to regulate pH)
-Add the amylase to starch solution and add it to spotting tile at regular intervals
-Add iodine solution to test for starch- when it stops turning blue/black all the starch has reacted
The structure of enzymes
Globular proteins
-Specific tertiary structure determines shape of active site, complimentary to specific substrate
Function of enzymes
-Biological catalyses for intra and extracellular reactions
-Formation of enzyme substrate complexes lowers activation energy of metabolic reactions
The induced fit model affect on enzyme action
-Shape of active site is not directly complimentary to substrate and is flexible
-Conformational change enables enzymes substrate complexes to form
-This puts strain on substrate bonds, lowering activation energy
how does substrate concentration affect the rate of reaction?
-Enzyme concentration is fixed, so rate increases proportionally to substrate concentration
-Rate levels off when maximum number of enzyme substrate complexes form at any given time
How does enzyme concentration affect rate of reaction?
-Substrate is in excess, rate increases proportionally to enzyme concentration
-Rate levels off when maximum number of enzymes,e substrate complexes form at any given time.
How does temperature affect rate of reaction?
-Rate increases as kinetic energy increases and peaks at an optimum temperature
-Above optimum, ionic and H- bonds in tertiary structure break= active site no longer complimentary to substrate (denaturation).
How does pH affect the rate of reaction?
-Enzymes have a narrow optimum pH range
-Outside range H+/OH- ions interact with H- bonds and ionic bonds in tertiary structure= denaturation.
How do competitive inhibitors work?
Bind to active site since they have similar shape to substrate.
Temporarily prevent enzyme substrate complexes from forming until released.
-Increased substrate concentration decreases their effect.
How do non competitive inhibitors work?
-Binding at allosteric binding site
-Trigger conformational change of active site
-Increasing substrate concentration has no impact on their effect
How to work out initial rate of reaction on a graph
Calculate gradient of tangent at t=0
Why is it advantageous to calculate initial rate?
Represents maximum rate of reaction before concentration of reactants and end-production inhibition.
Investigating enzymes: Trypsin
- Take three test tubes and measure 5cm3 milk into each. Place in water bath at 10°C for 5 minutes to equilibrate.
- Add 5cm3 trypsin to each test tube simultaneously and start the timer immediately.
- Record how long it takes for the milk samples to completely hydrolyse and become colourless.
- Repeat steps 2-3 at temperatures of 20°C, 30°C, 40°C and 50°C.
- Find the mean time for the milk to be hydrolysed at each temperature and use this to work out the rate of reaction.
