BIOLOGICAL MOLECULES - enzymes Flashcards
what are enzymes?
Enzymes are biological catalysts for intra and extracellular reactions.
The specific tertiary structure determines shape of active site, complementary to a specific substrate
The formation of enzyme-substrate complexes lowers activation energy of metabolic reactions.
explain the induced fit model of enzyme action?
Shape of active site is not directly complementary to substrate and is flexible. Conformational changes enable enzyme-substrate complexes to form. This puts strain on substrate bonds, lowering activation energy.
How have the models of enzyme action changed?
Initially there was the lock and key model which said that the substrate is complementary to the active site. Active site is only complementary to one substrate.
Currently: now the induced fit model is used. It also explains how binding with allosteric sites changes the shape of active site.
Name 5 factors can affect the rate of enzyme controlled reactions?
- enzyme concentration
- substrate concentration
- concentration of inhibitors
- pH
- temperature
How does substrate concentration effect the rate of reaction?
-Given that enzyme concentration is fixed, it increases the rate of reaction proportionally.
-Rate of reaction slows down when enzyme concentration becomes a limiting factor.
-The rate levels off when there are maximum numbers of enzyme-substrate complexes.
How does enzyme concentration effect the rate of reaction?
Given that substrate is in excess, the rate of reaction will increase proportionally to enzyme concentration.
Increasing enzyme concentration increases the number of active sites available for the substrates to collide with.
Rate of reaction decreases when the substrate becomes a limiting factor.
How does temperature effect the rate of reaction?
As temp increases there is more kinetic energy so the molecules move faster increasing the number of collisions and therefore the number of enzyme- substrate complexes formed increases. Therefore the rate of reaction increases.
Each enzyme has optimum temperature.
Once optimum temperature is reached the rate of reaction will decrease as molecules vibrate too much and the ionic and hydrogen bonds which maintain the tertiary structure are broken.This changes the shape of the active site and no more ES complexes can be formed. The enzyme is permanently denatured and the reaction stops.
How does pH effect the rate of reaction?
If the enzyme is in above or below the optimum pH level then the H+ or OH- ions disrupt the ionic and hydrogen bonds holding the enzymes tertiary structure in place.
At extreme pH levels the enzymes active site changes shape and no more ES complexes can be formed as the substrate no longer fits. The enzyme is permanently denatured.
what are competitive inhibitors?
Competitive inhibitors have similar shape to the substrate. It competes with the substrate and binds with the active site.They block the active site so the substrate cannot bind and no ES complexes can be formed.
Increasing the substrate concentration decreases the effect of competitive inhibitors.
what are non - competitive inhibitors?
They bind to an allosteric site which changes the shape of the active site so it is no longer complementary to the substrate. So no ES complexes are formed.
How do you calculate rate of reaction from a graph?
calculate the gradient
draw a tangent then calculate the gradient
outline how to calculate the rate of reaction from raw data?
change in concentration of product or reactant / time
why is it advantageous to calculate initial rate?
represents maximum rate of reaction before concentration of reactants decreases.
state the formula of pH?
pH= -log10[H+]
