1.4 enzymes Flashcards
key enzyme facts
-they’re not used in chemical reactions
- they’re not changed
- they have a high turnover
- enzyme reactions have limiting factors
-specific
what does having a high turnover mean
they catalyse many reactions per second
what do we need enzyme reactions for
metabolism
(all reactions in the body)
structure of an enzyme
tertiary proteins, globular, metabolic functions
what is a biochemical/metabolic pathway
a sequence of enzyme-controlled reactions in which a product of one reaction is a reactant in the next
what does anabolic mean
building up molecules
(protein synthesis)
what does catabolic mean
breaking down molecules
(digestion)
what is activation energy
the energy needed to start chemical reactions
what doe enzymes do to the activation energy
they lower the activation energy, we don’t need heat for the reactions to occur
what do enzymes do to chemical reactions
they act as catalysts by lowering the activation energy needed to drive the reaction
where is lysozyme found and what is it an example of
found in tears, its secreted by many different cells and it breaks down bacterial cell walls
an example of the induced-fit model
what is successful collision
where the substrate collides with the active site
two types of enzymes
-intracellular
-extracellular
what does intracellular mean and an example of one
working within the cell
catalase
what does extracellular mean and an example of it
working outside the cell
digestive enzymes
what does the lock and key hypothesis suggest
that there is an exact fit between the substrate and the active site of the enzyme
explain induced fit hypothesis
the active site is not the right shape to begin with. substrate molecule changes the shape of the active site to fit the substrate molecule perfectly
a substrate can mold the enzyme to its own shape so several substrates can react with the same enzyme
what bonds help to maintain the 3D globular shape of the enzyme
disulphide bonds, helps maintain the active site
what does the substrate have
a complimentary shape that fits into the active site
why is it important that enzymes are efficient
because they have a high turnover number which means they can convert many molecules of substrate into product per unit time.
what factors affect enzyme activity
temperature/pH/substrate concentration/enzyme concentration
how does an temperature affect enzyme activity
an increase in temperature gives molecules greater kinetic energy so enzyme and substrate molecules move around more quickly. this increases the chance of collision and will lead to more successful enzyme-substrate complexes. therefore increases the rate of reaction
optimum temperature for most enzymes?
40
what can happen with changes to the pH
small changes can affect the rate of reaction without affecting enzyme structure, but small changes outside the optimum range can cause reversible changes in the enzyme structure.
extremes of pH can denature an enzyme
how does enzyme concentration and substrate concentration affect rate of reaction
when will the reaction level off
if the enzyme concentration remains constant the rate of reaction will increase as the substrate concentration increases. it will level off once all the active sites are occupied, the number of available active sites become a limiting factor at higher substrate concentrations.
explain how the substrate concentration being the limiting factor can change
(in terms of a graph)
initially the substrate concentration is the limiting factor, when the curve levels off the substrate is no longer limiting the rate of reaction, another factor will be the limiting factor (enzyme concentration)
what happens when enzyme concentration becomes a limiting factor
all the active sites are occupied, having formed successful enzyme-substrate complexes
what is the turnover number
the number of molecules that one enzyme molecule can turn into products in a given time
what happens as enzyme concentration increases
there are more active sites available and therefore the rate of reaction increases
what is a limiting factor
when an increase in its value causes an increase in the rate of reaction
how can you keep temperature constant
use an electronic thermostatically controlled water bath
what is Vmax
is the maximum velocity or rate of reaction for an enzyme
what does a higher concentration of enzyme mean
would mean a higher overall rate of reaction. the initial rate would be faster and it would level off at a higher point
what does a lower concentration mean
a reduced rte of reaction. the initial rate would be slower and it would level off at a lower rate
what is an enzyme inhibitor
2 types?
any substance which decreases the rate of an enzyme catalysed reaction or that stops it
competitive/non-competitive
how does a competitive inhibitor work
They are structurally similar to the substrate molecule. it can fit in the active site of the substrate molecule. a competitive inhibitor prevents enzyme-substrate complexes forming.
what will increasing the substrate concentration
do in the presence of a competitive inhibitor?
will decrease the effect of the inhibitor as the enzyme is more likely to collide with a substrate molecule and form a successful enzyme-substrate complex
what do non-competitive inhibitors do
they don’t bind to the active site, they bind to other parts of the enzyme. this alters the overall shape of the enzyme molecule including the active site. the substrate molecule can no longer fit into the active site
what will increasing the substrate concentration do?
(non-competitive inhibitors)
it won’t increase the rate of reaction in this case as the substrate can no longer fit into the enzyme’s active site. so successful enzyme-substrate complexes cannot form
example of a non-competitive inhibitor
cyanide
what is the area of the enzyme that is not the active site called?
allosteric region
what will happen to the rate of reaction with non-competitive inhibitors
the enzymes active sites are now the wrong shape, the max rate of reaction falls because the concentration of active enzyme has been reduced
what is end-product inhibition
where the final product in the pathway inhibits an early-stage enzyme
what is the effect of end-product inhibition
reduces the rate of the metabolic pathway
role of immobilised enzymes
to restrict enzyme mobility in a fixed space
definition of an immobilised enzyme
enzyme molecule bound to an inert material over which the substrate molecules move
properties of immobilised enzyme
example of one
fixed on a inert matrix
alginate beads
benefits of immobilising enzymes
(any4)
1-enzyme doesn’t contaminate the product
2-immobilised enzyme can be reused
3-only a small quantity of an enzyme is needed
4- enzymes are more stable
5-can catalyse reactions over a wider range of pH
6- more than one enzyme can be used
7- greater control over the enzyme
8-can be used in a continuous process
9-easy to purify product
what does a biosensor do? how are enzymes involved?
gives an indication of how much chemical is in the blood/urine (glucose) even at low concentrations
uses enzymes to detect the presence of tiny quantities of specific enzymes
what is a transducer
it can convert energy from one form to another, it detects chemical energy when substrate is broken down by an enzyme
explain how a biosensor will work
they use immobilised enzymes on age membrane. the biosensor detects a chemical change, a substrate is converted to product, and a transducer converts this chemical change into an electrical signal which can be amplified and viewed on display
