Enzymes Flashcards
what are enzymes
they are biological catalysts as they speed up reactions by lowering the activation energy for chemical reactions.
how do enzymes lower activation energy
they help align reactants through the formation of enzyme substrate complexes. This allows reactions to take place at lower temperatures.
what are enzymes structure.
specific 3D tertiary structure to give them a specific active site that is only complementary to specific substrates.
what is the induces fit model
the model that suggests an active site is not fully fixed and that a substrate can induce a change in the enzymes active site’s shape to make it complementary.
what are the four stages of the induced fit model.
the substrate enters the active site.
the binding of the molecule changes the 3D tertiary structure of the active site.
this puts stress on the bonds which causes them to break more easily - thus explains how the enzymes lower activation energy.
when the substrate leaves the active site it then returns to its previous shape to allow it to bind to other substrates.
what effects enzyme activity
temperature pH concentration of enzymes concentration of substrates inhibitors
what is the word that describes the temperature at which enzymes work at their best
Optimum
why can an increase in temperature increase but also decrease enzymes rate of reaction.
As temperature increases so does kinetic energy so the substrates and enzymes have more kinetic energy and so are more likely to collide and form enzyme substrate complexes.
However if the temperature exceeds the optimum then the hydrogen bonds holding the tertiary structure can break, thus changing the active site making it no longer complementary to it’s substrate ( denatured).
how does pH effect enzyme activity.
if the pH alters from it’s optimum then the charge on the R group of the amino acids are altered and hydrogen and ionic bonds in the tertiary structure are broken.
describe the effect of substrate concentration
as substrate concentration increases then so does the rate until it eventually plateau’s.
explain the effect of substrate concentration on rate
the rate gradually increases as more enzymes active sites become full - substrate conc is the limiting factor.
as the substrate concentration becomes so high all the enzymes active sites are filled - the enzymes become the limiting factor.
effect of enzyme concentration.
the more enzymes the more likely collisions become and so the more likely there is to be enzyme substrate complexes.
however if the amount of substrate becomes the limiting factor the enzyme concentration will have no effect.
what are the two types of inhibitors.
competitive
non-competitive
how to competitive inhibitors work.
they have a similar structure to the substrate
they bind to the active site but do not react.
this prevents enzyme substrate complexes from forming.
how do non-competitive inhibitors work.
they bind to a site on the enzyme other than the active site.
This alters the shape of the active site and so the substrate can’t fit.
No enzyme substrate complexes can form and so the rate decreases.
