enzymes Flashcards
1
Q
role of enzymes
A
- catalyse anabolic reactions (growth)
- catalyse catabolic reactions (breaking down)
- catalyses digestion
- enzymes allow metabolic reactions
- increase ROR up to Vmax
2
Q
specificity
A
- each enzyme catalyses one biochemical reaction
3
Q
how do enzyme inc ROR
A
- mol collide successfully
- reduce the activation energy required to react
4
Q
lock and key hypothesis
A
- substrate binds to its complementary active site
- enzyme-substrate complex formed
- substrates react
- products formed in an enzyme-product complex
- products released
- enzyme unchanged and undergoes further reaction
5
Q
induced fit hypothesis
A
- enzyme changes shape as the substrate enters
- initial interaction between the enzyme and substrate is weak
- induces changes in tertiary structure of enzyme
- strengthens binding
- strains substrate mol
- weakens bonds in the substrate
- lowers Ea required
6
Q
intracellular enzymes
A
- structure + functions of cells + organisms.
- enzyme catalase
- breaks down H2O2 into O2 + H2O
7
Q
extracellular enzymes
A
- enzyme amylase
- starch broken down into maltose
- salivary glands
- pancreatic juice in small intestine
- enzyme maltase
- maltose broken down into glucose
- small intestine
- enzyme Trypsin which is a protease
- catalyses digestion of proteins into peptides
- then into amino acids by other proteases
- pancreas
- released in pancreatic juice into small intestine
8
Q
effect of temp on enzymes
A
- inc temp, increses KE
- particles move faster, collide more frequently
- more freq successful collisions between substrate and enzyme
- more ESC formed
- temp too high, bonds strain and break
- changes tertiary structure of the protein
- denatured
- active site changes shape so substrate isn’t complementary
- enzyme isn’t a catalyst
- optimum temp have the highest rate of activity
9
Q
temperature coefficient
A
- Q10
- measure of how much ROR inc with a 10°c rise in temperature
- doesn’t apply to denatured enzymes
- Q10 = R2/R1
10
Q
cold temp
- thermophiles
A
- enzymes adapted to cold
- more flexible structures
- less stable
- small temp changes will denature them
- thermophiles live in very hot env
- enzymes are more stable
- increases number of H-bonds + disulphide bonds in tertiary structures
- shape of AS + protein is more resistant to change
11
Q
pH effect on enzymes
A
- change in pH is a change in H+ conc
- optimum pH is where the AS is the right shape at a certain H+ conc
- when pH changes, shape of enzyme + AS changes
- when pH returns to optimum, protein returns to normal shape (renaturation)
- if pH has a significant change, structure is irreversibly altered + denatured
12
Q
substrate/enzyme conc
A
- inc substrate = higher collision rate with AS
- more ESC
- inc ROR
- inc enzymes
- inc available AS
- more ESC
- faster rate
13
Q
what are inhibitors
A
- prevent enzymes from carrying out their normal function of catalysis
- competitive + non-competitive
14
Q
competitive inhibition
A
- mol with similar shape to substrate
- fits into active site
- blocks the substrate from entering AS
- prevents enzyme catalysing the reaction
- enzyme can’t carry out its function
- inhibited
- substrate + inhibitors compete to bind to the AS
- slows ROR bc less ESC formed
- only bind temporarily so effect is reversible
- exception = aspirin
15
Q
effect of competitive inhibition on ROR
A
- reduces ROR
- doesn’t change Vmax
- if subs conc is inc
- more subs than inhibitor
- Vmax can still be reached
16
Q
competitive inhibition examples
A
- Statins competitively inhibit enzymes
- which synthesise cholesterol
- reduce blood cholesterol conc
- aspirin irreversibly inhibits the AS of COX enzymes
- prevents synthesis of thromboxane + prostaglandins
- produce pain + fever
17
Q
non-competitive + effect on ROR
A
- inhibitor binds to allosteric site
- tertiary structure of enzyme changes
- AS changes shape
- not complementary
- unable to bind
- enzyme can’t carry out functions so is inhibited
- inc conc of enzyme/substrate wont help
- inc conc of inhibitor will dec ROR
- more AS unavaliable.
18
Q
example of non-competitive
A
- organophosphates used as insecticides + herbicides
- irreversibly inhibits acetyl choline esterase
- necessary for nerve transmission
- muscle cramps, paralysis
- proton pump inhibitors
- treat long term indigestion
- irreversibly block enzyme system that secretes H+ into the stomach
- reduce production of excess acid
19
Q
end product inhibition
A
- product of reaction = inhibitor to the enzyme that produced it
- negative feedback control mechanism
- excess products aren’t made
- resources aren’t wasted
- non competitive, reversible inhibition
20
Q
example of end product inhibition
A
- respiration catalysed by phosphofructokinase
- non-competitively inhibited by ATP
- ATP conc high, more ATP binds to allosteric site of PFK
- prevents addition of second P-group to glucose
- glucose isn’t broken down
- ATP not produced at same rate
- As ATP is used up
- less binds to PFK
- enzyme can catalyse Rt
- adds second P-group to glucose
- respiration continues
- more ATP produced
21
Q
cofactors
A
- non-protein
- only work if another non-protein is bound to them
inorganic cofactors come from the diet as minerals (iron, calcium )
- Cl- is a cofactor for amylase
- prosthetic groups are cofactors (permanent + bind tightly)
- Zn2+ prosthetic group for carbonic anhydrase
22
Q
co enzyme
A
- organic cofactors (bind loosely)
- derived from vitamins
23
Q
precursor activation
A
- enzymes produced in inactive form (inactive precursor enzymes)
- PE undergo change in shape to be activated
- by addition of a cofactor
- before addition of CF precursor protein = apoenzyme
- ## when cofactor added = holoenzyme
