2.1 Enzymes Flashcards
definition of enzymes
proteins that are catalysts and speed up chemical reactions
metabolism
is the overall chemical activity of cells
substrate
the molecule on which an enzyme acts.
denaturation
an irreversible change in protein structure.
what is a catalyst?
speeds up (catalyses) chemical reactions that would otherwise take place, but much more slowly.
8 things about enzymes
1) are proteins
2) are substrate specific
3) can be reused over and over again
4) are needed in small amounts and are neither reactants or products
5) reduse activation energy required (make a reaction take place more easily)
6) can catalyse a reaction in either direction (most chemical reactions are reversible)
7) do not change the direction of a reactant
8) do not change the final amount of product
describe the active site and its role.
The active site is a particular position/specific site on an enzyme which attaches to a specific substrate.
what are enzymes
• enzymes increase the rate of chemical reactions which would otherwise occur too slowly to sustain life • enzymes lower the activation energy required for a reaction to proceed.
two processes of enzyme activity
1) LOCK AND KEY - substrate molecules have the right shape to fit an enzyme
2) INDUCED FIT - actual interactions between substrate and enzyme changes the shape of the enzyme to produce the right fit.
activation energy
energy required to start a chemical reaction
what do chemical reactions involve?
breaking and remaking chemical bonds.
the molecules require a certain amount of activation energy to get the reaction started
two factors that affect chemical reactions
1) amount of substrate or enzyme present
2) whether there is an accumulation of product.
however given an unlimited time, the final amount of product in not affected by the amount of enzymes present
6 factors which affect enzymes
1) Temperature
2) pH
3) Regulating enzyme affinity
- chemical inhibition
- amounts of reactants
- coenzymes and co factors
Temperature
- warming increases the rate of most chemical reactions, including enzyme catalysed reactions
- warm = molecules moving faster more substrate and enzyme interactions
- cooler = molecules moving at a slower pace, less particle interactions
- hot = denaturisation
what is denaturation?
- irreversible change in the protein structure
- boiling denatures most enzymes, which is why some vegetables are blanched in boiling water before freezing.
- the boiling water deactivates enzymes which would otherwise cause the vegetables to deteriorate during storage.
optimum temperature
range in which the temperature at which the enzymes catalytic activity is the greatest.
- range immediately below the critical temp
- optimal temp for particular enzymes may vary in different species and are related to the normal body temp of enzymes.
critical temperature
range at which denaturation of enzymes begin to occur
how does pH affect enzymes
- three dimensional structure of proteins is affected by pH
- altering the pH may change the shape of the binding ( active site) and so alter the ‘fit’ between enzyme and substrate
what is optimal pH
that at which the fit is best and so the enzyme activity is the greatest
- for many enzymes this is a neutral or sightly acidic pH.
what is affinity?
is the ease at which an enzyme binds with its substrate
how do cells regulate enzyme affinity and what is it?
- cells can regulate the affinity by of certain key enzymes for their substrate molecules
- they do this by attracting other molecules to the enzyme to alter the shape of its active site.
this allows to increase or decrease the rate of a reaction in particular circumstances
chemical inhibition
other chemical substances can inhibit enzyme function by binding to the active site of the enzymes, or by combining with another part of an enzyme in such a way that the shape of the binding site is altered
How does the amount of reactant affect the enzyme
rate of a reaction is also affected by the relative amounts of substrate or enzyme present and how much product has accumulated
- if there is more substrate present = net reaction will go to the right
- if product accumulates = the net reaction will slow and eventually begin to go to the left
Coenzymes and Cofactors
- coenzymes are very small organic molecules - less complex than proteins - that are associated with particular enzymes and are essential for their activity.
what does metabolism involve
it includes the manufacture ( synthesis) of organic molecules, various energy transformation and recycling processes, and the breakdown of unwanted substances
