enzymes Flashcards
what are enzymes
globular proteins that act as catalysts and catalysts alter the rate of chemical reactions without undergoing permanent change
what must there be for a reaction to take place
- molecules must collide with sufficient energy to alter arrangement of their atoms
- activation energy is required
what is activation energy
the minimum energy needed for a reaction to take place
how do enzymes work
they lower the activation energy which allows reactions to take place at lower temperatures
what is the induced fit model
the active site forms as enzyme and substrate interact
the enzyme is flexible and can mould itself around substrate
as it changes shape the enzymes puts a strain on substrate molecule
strain distorts the bonds on substrate and lowers the activation energy needed to break the bond
how do you measure the rate of enzyme action (on a graph)
first draw a tangent then calculate the gradient
what is the effect of temperature on enzyme action
more temperature increases kinetic energy of molecules
molecules collide more often
more successful collisions
more enzyme substrate complexes formed
how does pH affect enzyme action
change in pH alters the charges on the amino acids that make up active site of enzyme
substrate can no longer become attached to active site
enzyme substrate complexes cant be formed
may cause bonds maintaining tertiary structure to break
active site changes shape
what is the effect of enzyme concentration on rate of reaction
increase in enzyme leads to proportionate increase in rate of reaction (excess substrate)
there is more substrate than enzymes active site can deal with which increases the rate of reaction
an increase in enzyme concentration means that excess substrate can also be acted on
is substrate is limiting an increase in enzyme concentration will have no effect because there is not sufficient substrate to satisfy all enzymes active sites at one time
how does pH affect enzyme action (chemically)
arrangement of active site is determined by hydrogen and ionic bonds between NH2– and —COOH groups of polypeptide that make the enzyme
change in H+ ions affect bonding
therefore the active site changes shape
how does substrate conc affect enzyme action
rate of reaction increases in proportion to substrate
low substrate concentrations means enzymes have a limited number of substrate molecules to collide with and the active sites of enzymes not working to full capacity
as more substrate is added active sites gradually become more filled until they reach v.max
after v.max addition of substrate will have no effect
what is an inhibitor
a substance which prevents an enzyme from catalysing its reaction
how do competitive inhibitors work
the inhibitor enters the environment of the enzyme
due to kinetic energy all of the molecules are moving around
sometimes an inhibitor arrives at an active site before a substrate
the shape on the inhibitor matches with the shape of the substrate
the inhibitor binds with the enzymes active site preventing a substrate from binding
how do non-competitive inhibitors work
the inhibitor enters the environment of the enzyme
the shape of the inhibitor is different to the shape of the substrate
the shape of the inhibitor does however match with a different part of the enzyme
the inhibitor binds with this site causing a reaction with this site causing a reaction to occur which alters the enzymes tertiary structure
the substrate can no longer fit in active site
if inhibitor is reversible it can dissociate with the enzyme allowing the enzyme to regain its tertairy structure
