enzymes Flashcards
name 8 features of enzymes
- they act as biological catalysts (not used up in a reaction)
- all enzymes are globular proteins
- enzymes posses an active site and can form enzyme substrate complexes
- enzymes can catalyse forward or backward reactions (reversible)
- enzymes can remain unchanged by the reaction they catalyse
- only a very small number of enzyme molecules are needed
- enzymes can be inhibited
- enzymes may be denatured
know the role of amino acids in enzymes
Enzymes are proteins comprised of amino acids linked together in one or more polypeptide chains. This sequence of amino acids in a polypeptide chain is called the primary structure. This, in turn, determines the three-dimensional structure of the enzyme, including the shape of the active site.
what do many enzymes end in
ase
- E.g. catalyse, maltase
what part fits into the active site of an enzyme
the substrate
what are the two enzyme fit theories
- lock and key
- induced fit theory
intracellular enzyme action
inside the cell
what do enzymes do
they speed up the rate of reaction by being catalyst, by reducing the activation energy
what does catalyse break hydrogen peroxide down to
oxygen and water
what is extracellular enzyme action
the enzyme, is used outside of the cell it was made
what is the structure of globular proteins
hydrophobic amino acids surrounded by hydrophilic amino acids
- remember this is why they are soluble in water
what is the enzyme substrate complex
The enzyme substrate complex is a temporary molecule formed when an enzyme comes into perfect contact with its substrate
what do we call the active sites bond to the substrate
specific/complementary fit
why is the activation energy important
it must be reached in order for a reaction to take place, in order to form a product
what does the tertiary structure do in order to form the active site?
it folds, in order to form a three dimensional shape
what has to happen, in order to produce product
the a substrate must successfully react with the active site.
what dictates the rate of an enzyme controlled reaction
the frequency of successful collisions between the substrate molecules and the active site
why is temperature important, in enzyme controlled reactions
to high a temperature will lead to the enzyme denaturing due to there being to much kinetic energy causing vibrations, that would sperate the tertiary structure bonds, whilst too low of a temperature would mean that there would be a to little kinetic energy, resulting in a low rate of reaction
what happens at the optimum temperature
we have the maximum frequency of successful collisions between the substrate and the active site
can we reactivate denatured enzymes
NO
how do we work out Q10 and what value is Q10 normally
it is normally a value of around 1, but only below the optimum temperature of the enzyme
how can we contour act the impact of a competitive inhibitor
by increasing the substrate concentration
how does one, lower the activation energy
by using enzymes ( as a biological catalyst)
- what is the equation for initial rate
and - how is calculated
- change in y/ change in x
- by drawing a tangent at time= zero
why does increasing enzyme concentration increase rate?
- more active sites available
- more frequent collisions
- more enzyme substrate complexes formed
- greater rate, due to more product being formed per second
what is a control variable
A control variable is anything that is held constant or limited in a research study
effect of increasing substrate concentration
- more successful collisions (between active site and substrate
- more enzyme substrate complex’s formed
- greater rate, due to more product being made per second
what is a buffer
chemicals, that are resistant to a change in pH
what doe enzyme inhibitors do?
reduce the rate of enzyme controlled reactions because they have an effect on enzyme molecules
what is a competitive inhibitor
mostly reversible and if binding irreversibly they are called inactivators
what are 3 key things about competitive inhibitors
- have close structural resemblance to substrate of enzyme
- compete with substrate for active site
- increasing substrate conc, relative to inhibitor conc, then the initial rate increases
give one example of a competitive inhibitor
statins, a drug used to treat coronary heart disease
what is a non - competitive inhibitor
does not compete for the active site it has equal affinity (willingness to bind) for the enzyme and enzyme substrate complex
what are the 5 key things about non - competitive inhibitors
- it has no structural similarity to the substrate
- combines with enzyme at a point other than active site (allosteric active site)
- active site becomes distorted (substrate no longer fits)
- when inhibitor saturation is reached the rate of reaction is almost nil
- increasing substrate conc will not affect the rate of reaction
what is a key thing to remember with non - competitive inhibitors
- increasing the substrate concentration, does not increase the reaction rate.
what is an anabolic enzyme
the building up/ synthesis
what is a catabolic enzyme
the breaking down/degradation
what is the general enzyme equation
Enzyme + Substrate ↔ Enzyme Substrate Complex ↔ Enzyme Product Complex ↔ Enzyme + products
what is a prosthetic group
tightly bound to an enzyme permanently, often contains metal ions
what are inorganic ions
not permanently bound to the enzyme, may bind temporarily to either the enzyme or the substrate
what is a coenzyme
they bind to the active site, for short periods of time, before or at the same time as the substance they are organic, non - protein molecules
what are respiratory enzyme responsible for
the breakdown of glucose and the formation of ATP
phosphorylases act in cytoplasm
phosphorylates, add phosphate groups to glucose, to keep it in the cell + make it more reactive.
decarboxylases and dehydrogenase act in the matrix of the mitochondria
aerobic respiration - decarboxylases remove carbon dioxide from a molecule and dehydrogenates remove H from a molecule
what makes ATP
ADP + PI -> ATP
suggest the advantages of having an internal digestive system compared with secreting enzymes outside the organism
- extracellular enzyme, secreted outside of an organism are lost to the environment
- internal environment, can be regulated, to give optimum conditions.
how do enzymes lower activation energy
- by orientating molecules, so that reacting bonds are near to each other
- R groups, on the enzyme may donate or accept electrons, for oxidation/ reduction reaction.
- water, may be excluded from the reaction, due to the hydrophobic R groups in the active site, this creates more favourable conditions for the reaction
know how to measure the rate of enzyme controlled reactions
what is the calculation to work out initial rate of reaction
rate = change in Y/ change in X
why is enzyme concentration, usually relatively low, in cells
- enzyme can be reused
- genes for enzymes can be switched on if required
why must we keep pH and Temperature, constant when investing the rate of reaction, when changing the enzyme concentration
- only changing the enzyme concentration
- control Ph using a buffer
- controlled temp, by using a thermostatically controlled water bath.
what happens, when we increase the substrate concentration
- more successful collisions between active site + substrate
- more enzyme substrate complexes’
- more product made per second
- greater rate
what is Vmax
the maximal reaction rate or velocity of an enzymatically catalyzed reaction when the enzyme is saturated with its substrate.
reversible inhibitors
- most competitive inhibitors do not bind permanently to the active site
- they bind for short periods and then leave
- removal of inhibitor from a reaction mixture, leaves enzyme molecule unaffected
irreversible inhibitors
- many non - competitive inhibitors bind permanently to enzyme molecules
- inhibition cannot be reversed an any molecules bound by the inhibitor are inactivated.
- inhibition is not always a bad thing, as it can help to control metabolic reactions
what is one thing to note about inhibition
inhibition is not always a bad thing, as it can help to control metabolic reactions
