enzyme action Flashcards
what are enzymes
biological catalysts
what reactions do enzymes catalyse
metabolic reactions at both cellular level (respiration) and for the organism as a whole (e.g digestion)
is enzyme action intracellular or extracelular
both- inside and outside of cells
what type of molecule are enzymes
proteins
what is activation energy
the amount of energy needed to be supplied to the chemicals before the reaction will start- often provided as heat
what do enzymes do to the activation energy
lower the energy required for the reaction to happen meaning the reaction happens faster
what lowers the activation energy
when an enzymes active site fits with a substrate to form an enzyme substrate complex
how does an enzyme substrate complex lower activation energy
1- if two substrate molecules need to be joined, being attached to the enzyme holds them closer together, reducing any repulsion between the molecules so that they can bond more easily
2- if the enzymes is catalysing a breakdown reaction, fitting into the enzyme active site puts a strain on the bonds in the substrate so that the substrate molecule breaks up more easily
whats the induced fit model
- as the substrate binds, the enzyme changes shape slightly to form an enzyme substrate complex, then releasing the products
- the enzyme then returns to its origional shape until another substrate binds to it
how specifically shaped are enzymes
very specific, they only bind to one specific substrate
what structure is the active site deturmined by
tertiary structure
do enzymes all have the same tertiary structure
no, each enzyme has a different tertiary structure, producing a different active site as they are all specific to catalysing one reaction and can only form an enzyme substrate complex with one substrate
what happens if the tertiary structure is altered
the enzyme substrate complex cannot be formed
what can alter the tertiary structure
pH or temperature
how can genes effect the structure of enzymes
- the primary structure of a protein is determined by a gene
- if a mutation occurs it could change the tertiary structure of the enzyme produced
how does temperature influence enzyme activity
- rise in temperature makes the enzymes molecules vibrate more
- if the temperature goes above a certain level this vibration breaks some of the bonds that hold the enzyme in shape
- at this point the enzyme is denatured and no longer acts as a catalyst
how does pH influence enzyme activity
- most human enzymes work best at pH 7
- above or below the optimum pH, the H+ and OH- ions found in acids and alkalis can mess up the ionic and hydrogen bonds that hold the enzymes tertiary structure
- this makes the active site change shape and the enzyme is denatured
how does enzyme concentration effect enzyme activity
- the more enzyme molecules there are, the more likely there will be collisions to form an enzyme substrate complex
- increasing rate of reaction
- if the substrate concentration is limited, and theres more than enough enzyme to deal with the substrate then there comes a point when adding more enzyme will have no effect
how does substrate concentration effect the rate of reaction
- higher the substrate concentration, more collisions and higher rate of reaction
- up until saturation point when all enzyme active sites are full
- the substrate concentration decreases over time during a reaction, unless more substrate is added. So if no other variables are changed then the rate of reaction will decrease over time too
- this makes the initial rate of reaction the fastest
how does competitive inhibition of enzymes work
- competitive inhibitor molecules are a similar shape to the substrate molecules
- they compete with substrates to form enzyme substrate complexes
- when the inhibitors bind to the enzyme no reaction takes place, however the active site becomes blocked and substrates can no longer bind
- if there is a high conc of inhibitor, then all of the active sites will become blocked reducing the rate of reaction
- if there is a high conc of substrate then theres more chance of the substrate binding which increases the rate of reaction
how does non- competitive inhibition work
- non competitive inhibitors bind to the enzyme away from its active site
- causes the enzyme to change shape making the active site no longer complimentary to the substrate
- increasing the substrate will now make no difference to the rate of reaction, as the enzymes are still inhibited
how do you work out the rate of reaction from a graph
by drawing a tangent and calculating the gradient
