Unit 3 - Enzymes Flashcards
What type of protein is an enzyme? [2]
- globular and water soluble
- tertiary structure with hydrophilic r group on outside and hydrophobic r group on inside
How do enzymes lower activation energy? [2]
- By holding substrate molecules close together
- placing a physical strain on the bonds so they are weaker and more easily broken
Where can enzymes act?
can be intracellular or extracelluar
Describe the induced fit model of enzymes [2]
- Substrate of active site changes to create a better fit or stronger binding to substrate
- substrate interacts with r groups of amino acids at active site of the enzyme
Describe the lock and key hypothesis
The substrate is complementary in shape to the enzymes active site and binds to it
State two ways to investigate progress of enzymatic reactions [2]
- analyse the amount of product from reaction is present
- analyse a colour change indicating removal or addition of product
How can we use colorimetry? [2]
Use a colorimeter to build a calibration curve of known concentrations.
Measure samples of reaction solution at equal time intervals and use curve to estimate conc of product
factors affecting enzyme reactions [5]
- Temp
- Enzyme conc
- substrate conc
- inhibitor conc
- Ph
effect of temp of enzyme activity [3]
- as temp increases substrate molecules gain more energy and more collisions happen
- it reaches a max optimum temp, after that enzyme begins to denature
- activity decreases
effect of ph on enzyme activity [2]
- at optimum enzyme activity is highest
- anything above or below messes with bonds in tertiary structure causes change of active site shape
function and importance of ph buffers [2]
- maintain ph by minimising changes to ph in a system
- important as product of a reaction may affect a systems ph
effect of substrate conc on enzyme activity [3]
- when substrate conc increases, enzyme activity increases as substrate conc is limiting
- more substrate results in more enzyme-substrate complexes formed
- beyond a certain point activity plateaus because all enzyme active sites are filled and vmax is reached
describe the mode of action of a competitive inhibitor [2]
- molecule similar in shape to substrate and complementary to active site and binds, blocking substrate
- increasing substrate reverses the inhibition
Mode of action of a non competitive inhibitor [2]
- Binds to allosteric site on enzyme causes active site to change shape
- irreversible and lowers rate of reaction and vmax (increasing substrate doesn’t do anything)
What is km and vmax? [3]
- represents the maximum rate of reaction by the system at max substrate concentration
- km is 1/2 vmax
- can be used to tell affinity of an enzyme to substrate (lower km = higher affinity)
Describe how an enzyme can be immobilised [2]
They are immobilized by attaching them to an insoluble, inert material.
This forms a gel capsule around them thus holding them in place during the reaction.
State the advantages of immobilising enzymes [4]
- More stable (can withstand diff Ph and temps)
- Easily separated after reaction
- Reusable
- Can be continually used
How do reactions of free enzymes differ to those of immobilised enzymes?
- immobilisation allows for increased resistance to denaturing conditions.
- this means that even if solution conditions change reactions will proceed to a larger range than if free enzymes were involved
