2.1.4 enzymes Flashcards
what are enzymes
enzymes act as biological catalysts to speed up metabolic reactions
what is an intracellular enzyme
an enzyme that works inside the cell
what is an example of an intracellular enzyme
catalase which breaks down toxic hydrogen peroxide into oxygen and water
what is an extracellular enzyme
an enzyme that works outside of cells
what is an example of an extracellular enzyme
amylase and trypsin
they are both used in digestion. amylase breaks down starch into maltose. trypsin hydrolyse peptide bonds turning long polypeptides into smaller ones.
what kind of protein are enzymes
globular proteins
how does an enzyme speed up rate of reaction
it lowers the activation energy so more particles are able to collide with enough energy to react
what is the active site of an enzyme
the part of the enzyme that the substrate molecules bind to. it has a specific shape.
what is the lock and key model
the substrate fits into the active site like a key in a lock to form an enzyme-substrate complex
what is the induced fit model
as the substrate binds to the active site, the active site changes shape slightly to fit the substrate more closely.
how does temperature effect enzyme activity
rate of an enzyme controlled reaction increases with temperature as the molecules have more kinetic energy so collisions are more frequent an have more energy
if temperature is too high enzymes denature as some bonds break and change the shape of the active site
what does the temperature coefficient show
it shows how the rate changes with temperature
what is the temperature coefficient (Q10)
Q10 = r2 (rate at higher temperature)/ r1(rate at lower temperature)
how does pH effect enzyme activity
all enzymes have an optimum pH value. above and below this the H+ and OH- ions can mess up the ionic bonds and hydrogen bonds in the tertiary structure so the enzyme denatures.
how does enzyme concentration effect enzyme activity
increasing enzyme concentration increases rate of reaction because more enzyme substrate complexes can form.
substrate concentration can be limited so there is a point where further increasing the enzyme concentration has no effect on rate
how does substrate concentration effect enzyme activity
the higher the substrate concentration the more likely a collision between enzyme and substrate is which means rate of reaction is increased
this is until a saturation point where all the active sites are full
substrate concentration decreases as the reaction goes on so rate of reaction will decrease over time.
how can we measure rate of an enzyme controlled reaction
- measure how fast the product is formed
- measure how fast the substrate is used up
what are cofactors
non protein substances that bond to enzymes to help them work
how do some inorganic ions work as cofactors
they help the enzyme and substrate bind together. they are not used up or changed in the reaction
what are organic molecule cofactors called
coenzymes
how do coenzymes work
they participate in the reaction and are changed by it. they often work as carrier molecules and are continuously recycled in this process
what is a tightly bound cofactor to the enzyme called
prosthetic group
what is competitive inhibition
when a similar shaped molecule to the substrate binds to the active site of an enzyme blocking it from the substrate.
what is non competitive inhibition
when a non competitive inhibitor binds to the allosteric site. this changes the shape of the active site so the substrate cant fit.
what make an inhibition irreversible
strong covalent bonds between enzyme and inhibitor
what makes the inhibition reversible
weak ionic or hydrogen bonds between the enzyme and inhibitor
how are some drugs enzyme inhibitors
- antiviral drugs can stop viruses replicating by inhibiting reverse transcriptase
- some antibiotics inhibit transpeptidase which stops the formation of proteins for the bacterial cell wall. this weakens the cell wall the cell bursts
how are some poisons inhibitors
cyanide, malonate, and arsenic all inhibit enzymes in respiratory reactions which causes cells to die.
what is product inhibition
when the product of a reaction inhibits the enzyme involved in the reaction
what is end product inhibition
when the end product of a metabolic pathway inhibits an enzyme that acts earlier on in the pathway
what is end product inhibition useful for
regulation metabolic pathways
how can enzyme inhibition be used to protect cells
enzymes can be synthesised as inactive precursors which are activated once the part of the precursor molecule is removed.
e.g. some proteases are made like this so they don’t damage proteins inside the cell
