M2 chapter 4: enzymes Flashcards
what is an enzyme?
protein that speeds up the rate of a chemical reaction. biological catalysts
what is a biological catalyst?
found in living organisms
what is a catalyst?
a substance which speeds up a chemical reaction without being used up in the reaction itself
what are intracellular enzymes?
enzymes that works inside a cell eg catalyse
what are extracellular enzymes?
enzymes that work outside a cell eg amylase and trypsin
what is the structure of enzymes?
globular proteins
have an active site which substrate binds to.
active site shape determined by proteins tertiary structure
what is a enzyme substrate complex?
a temporary molecule formed when the substrate with a specific complementary shape binds to the enzyme
how do enzymes speed up reactions?
they lower the activation energy needed for a reaction so they can happen at lower temperatures speeding up the rate of reaction
how does the enzymes lower the activation energy?
-if substrate molecule needs to break down the active site puts strain on the bonds between molecules so it can break more easily
-if substrate molecules need to bond together the active site pulls them closer together reducing repulsion making it easier to bond
what is the lock and key model?
The active site of an enzyme is structured to fit a specifically shaped substrate. Once the substrate binds to the active site, the enzyme will facilitate the reaction and release products of the reaction.
what is the induced fit model?
a substrate binds to an active site and both change shape slightly, creating an ideal fit for catalysis.
what factors affect enzyme activity?
temperature
pH
substrate concentration
enzyme concentration
how does temperature effect enzyme activity?
increase rate of reaction as more heat means more kinetic energy so the molecules move faster. this means the enzyme and substrates are more likely to collide and form an enzyme substrate complex
what is the optimum temperature for enzymes?
37 degrees Celsius
what else in the reaction does the temperature also increase?
energy of collisions meaning each collision is more likely to be a successful collision
what happens if the temperature gets too high?
reaction will stop because the enzyme molecules will vibrate too much which causes bonds which holds the enzymes shape to break
what is a Q10 value?
shows how rate of reaction changes when temperature in creases by 10 degrees
what effect does pH have on rate of reaction?
enzymes operate the fastest at an optimum pH usually pH 7.
what happens to enzyme activity when the pH goes above and below the optimum pH?
Above and below the optimum pH the H+ and the OH- ions break the hydrogen bonds which hold the enzymes tertiary structure in place. denaturing the enzyme
what effect does enzyme concentration have on enzyme activity?
more enzymes in a solution increases the rate of reaction because their is more enzymes for the substrate to collide with.
what is a saturation point?
when all the active sites are full so a higher concentration of enzymes or substrates wouldn’t make a difference
what effect does substrate concentration have on enzyme activity?
more substrate in a solution increases the rate of reaction because their is more substrate to collide with the active site
what is a cofactor?
a non protein substrate bound to an enzyme
what is a inorganic cofactor?
works by helping the enzyme and substrate bind together . it isn’t used up or changed in anyway
what is a organic cofactor?
Aka a coenzyme
participates in the reaction so is changed by it
move chemical groups between enzymes as carriers
what is a prosthetic group?
a cofactor which is tightly bound to the enzyme.
eg: zinc ions are a prosthetic group for carbonic anhydrase
what are enzyme inhibitors?
bind to enzyme to stop them from working
2 types- competitive and non competitive
what do competitive inhibitors do?
compete with substrate to bind to active site as it is the similar shape to block it
if high conc of inhibitor little substrate will bind to enzyme
what would a higher concentration of substrate effect a competitive inhibitor in a reaction?
faster rate of reaction to a certain point as more substrate can compete with the inhibitors to bind to the active site
what do non competitive inhibitors do?
bind to enzymes away from active site at allosteric site. cause active site to change shape so substrate can’t bind to it
what effect does a higher concentration of substrate have on a non competitive inhibitor?
no difference as the substrate can’t bind to the active site
what makes a inhibitor irreversible?
strong covalent bonds
what makes a inhibitor reversible?
weak hydrogen and ionic bonds
what sort of drugs are inhibitors?
antiviral drugs such as reverse transcriptase
antibiotics such as penicillin
what are metabolic poisons?
interfere with metabolic reactions in cells and can cause damage and death
what are some examples of metabolic poisons?
cyanide
malonate
arsenic
what is product inhibition?
when a product inhibits the enzyme that has catalysed its formation.
what is end product inhibition?
final product in metabolic pathway inhibits an enzyme that acts earlier on in pathway.
this regulates the pathway and controls the amount of end product made
Are product and end production inhibition reversible?
yes as levels of product decrease so do the levels of inhibition therefore enzyme can function again and more product can be made.
