enzymes Flashcards
what does amylase digest starch to
to maltose
what’s a cofactor
a substance that has to be present to ensure that an enzyme catalysed reaction takes place at an appropriate rate. some cofactors such as prosthetic groups are part of the enzymes structure, and others (mineral ion cofactors or organic coenzymes) form temporary associations with the enzyme
are inorganic molecule or ion cofactors used up
no, they dont participate in the reaction
what do cofactors help do
help the enzyme substrate bind together
example of a cofactor (inorganic ion)
Cl- (cofactors for the enzyme amylase)
what’s a prosthetic group in relation to an enzyme
a prosthetic group is where the cofactor is part of the enzymes structure
an example of a prosthetic group
Zinc ions (Zn^2+)
what is the prosthetic group Zn^2+ for
for carbonic anhydrase which catalyses the production of carbonic acid and Co2.
whats a coenzyme
a small organic non-protein molecule that binds temporarily to the active site.
- they are changed in reactions and recycled continuously
when is the enzyme-substrate complex formed
when a substrate molecule successfully collides with an enzyme molecule
explain the induced fit theory
when the substrate molecules fit into the enzymes active site, the active site changes its shape slightly to mould itself around the substrate molecule.
( subtle changes in R group allow for this)
what bonds bind the substrate to the active site
via hydrogen bonds, ionic attractions van der walls forces and hydrophobic interactions
what do enzymes do to the activation energy of a reaction
lower the activation energy thus speeding up the reaction
what are the 4 things affecting enzyme activity
temperature
pH
conc of substrate
conc of enzymes
how does temp cause enzymes to denature
- weak bonds incl hydrogen bonds and ionic bonds break that hold the tertiary structure of the enzymes active site together
- active site shape changes, substrates can no longer fit well
- at high temp, irreversible changes occur to tertiary structure thus enzyme denatured
what bonds allow for enzymes to be stable
more disulphide bonds
why does increasing rate of reaction beyond optimum temp reduce rate of reaction
due to breaking of bonds holding the active sites tertiary structure
how do u calc Q10
Q10= rate of reaction at T+10/ rate of reaction at T
Q10 is aprox at 2 what does this mean
for every 10 degree rise in temp, the rate of reaction is doubled
what happens if an enzyme is above or below optimum pH conditions
the H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure
how does enzyme conc affect rate of reaction
the more enzyme molecules there are in a solution, the more likely a substrate molecule will collide with an enzyme to form enzyme substrate complex- rate of reaction is increased
-if the amount of substrate is limited it comes to a point where theres more than enough enzyme molecules do deal with available substrate so adding more enzyme has no further affect
how dos substrate conc affect rate of reaction
the higher the substrate conc the faster the reaction, more substrate molecules- a collision more likely to occur thus more active sites used- this is up to the saturation point ( adding more substrate molecules would make no diff ass all active sites full)
- substrate conc = limiting factor, as it increases so does rate up to a certain point
- -substrate conc decreases after time unless more substrate is added so rate will decrease over time , this makes the initial rate the highest rate of reaction
simple: what are cofactors
non-protein substances
some cofactors are inorganic molecules or ions, what does this help
they help the enzyme substrate bind together -they dont take part in the reaction so are not used up or changed
give an example of a cofactor and what its a cofactor for
chloride ions are cofactors for the enzyme amylase
what’s a prosthetic group
a cofactor that is tightly bound to the enzyme , its part of the enzyme .
give an example of a prosthetic group
zinc ions (Zn^2+) are a prosthetic group for carbonic anhydrase, an enzyme in red blood cells which catalyses the production of carbonic acid from water and CO2.
what are the two types of inhibitors
competitive and non competitive inhibitors
what are competitive inhibitors and what do they do
- substances whose molecules have a simmilar shape to an enzymes substrate molecules.
- the competitive inhibitor fits into the active site so a substrate molecule cannot enter
- the amount of inhibition depends on the relative conc of a substrate and inhibitor molecules
- increasing the substrate conc dilutes the effect of the inhibitor
what are non- competitive inhibitors and what do they do
- molecules that bind away from its active site (this site is the allosteric site).
- this causes the active site to change shape so the substrate molecules can no longer bind to it.
- they dont “compete” with the substrate molecules to bind with the active site as they are a different shape.
- increasing the conc of substrate wont make a difference to the reaction rate- enzyme activity will still be inhibited
- they disrupt the enzymes tertiary structure
- some non competitive inhibitors bind irreversibly to the active site and others dont.
- the max rate of reaction is reduced by non-competitive inhibitors
what are metabolic pathways inhibited by
end product inhibition
what is a metabolic pathway
a series of connected metabolic reactions. the product of the first reaction takes place with the second reaction- each reaction is catalysed by a different enzyme
what is product inhibition
many enzymes are inhibited by the product of the reaction they catalyse
what is end product inhibition
end product inhibition is when the final product in a metabolic pathway inhibits an enzyme that acts earlier on in the pathway- controls the amount of end product that gets made unsure=(non-competitive inhibition but reversible)
both product and end product inhibition is reversible, what does this mean?
when the level of product starts to drop, the level of inhibition starts to fall so the enzyme can start to function= more product will be made
what are 2 examples of medicinal drugs as enzyme inhibitors
- antiviral drugs
- some antibodies
medicinal drugs as enzyme inhibitors: antiviral drugs (stop viruses like HIV)
-inhibits an enzyme which catalyses the replication of DNA , preventing viruses from replicating
medicinal drugs as enzyme inhibitors: antibodies
e.g penicillin inhibits an enzyme which catalyses the formation of proteins in bacterial cell walls. This weakens the cell wall and prevents the bacterium from regulating osmotic* pressure . As a result the cell bursts and the bacterium is killed
what do metabolic poisons do
they interfere with metabolic reactions causing damage, illness or death- theyre often enzyme inhibitors
what does malonone* and arsenic inhibit
the enzyme catalysing respiration
what is cyanide and what does it do
- highly toxic because it inhibits aerobic respiration and catalase
- KCN= toxic gas - when hydrolysed CN- ions bind irreversibly in mitochondria
what is snake venom and what does it do
- inhibits enzyme that is important at gaps between neurones and muscles to break down the neurotransmitter.
- if this enzyme is inhibited, paralysis occurs as muscles contract.
- if muscles involved in breathing are paralysed, the suffocating occurs.
