Enzymes Flashcards
what type of protein are enzymes
globular
how do enzymes increase the rate of a reaction?
lowers the activation energy, by e.g bringing reactants together to react
True or False unwanted products are produced by enzymes
false
How can cells regulate how quickly enzymes catalyze a reaction
increase/decrease the number of enzymes catalyzing the reaction = faster/slower reaction
define an enzyme
biological catalysts (1) that speed up the rate of reaction (2)in living organisms (3)
turnover number meaning
no. of reactions an enzyme can catalyse per second
The greater the activation energy needed the …. rate of of reaction. FIll in the blank
slower
What 2 things are needed for a reaction with an enzyme to occur
- collision of substrate & enzyme
- activation energy
how do enzymes reduce the activation energy
By straining the bonds in the susbtrate
intracellular enzymes
enzymes that work on the inside of a cell
extracellular enzyme
enzymes are released from the cell, to work outside the cell
extracellular enzymes example & use (1)
amylase digests starch into maltose
eexample of an extracellular enzyme & it’s use
trypsin breaks down protein s into smaller peptides
name 2 extracellular enzymes
amylase, tripase
name a intracellular enzyme
catalase
what is a intermediate molecule
formed from 2 or more substrates after being catalysed, then react further to give products
what is an enzyme substrate complex
enzyme molecule with substrate molecule in it’s actiev site, temporarily joined by non-covalent attraction. BEFORE reaction
what is an enzyme product complex
enzyme molecule with product molecule in it’s active site, temporarily joined by non-covalent attraction. AFTER reaction
what is the main suggestion that induced model makes that’s different from lock and key model
suggests active site isn’t a rigid structure
what bonds are present in the enzyme-substrate complex (in induced fit model)
hydrogen bonds, hydrophobic interactions ionic interactions, Van der Waals forces
what is different in the induced model to lock and key in terms of substrate bonding?
- subtle changes on amino acid’s R-Groups allows substrate to bond more effectively
what is different in the induced model after reaction?
- after reaction, products shape is slightly different to active site & can detach
what happens when pH changes & what effect does it have on the rate of enzyme activity
increase/ decrease in H+ ions from the optimum decreases the rate of reaction
how does H+ ions impact protein? (2)
- interferes with hydrogen and ionic bonding (due to charges) = disrupts the tertiary structure
- alters active site charges = substrate can’t bind
true or false not all enzymes have the same optimum pH?
true
true or false not all enzymes have the same optimum temperature?
false within THE SAME organism (37C body temperature)
optimum temperature defintiion
the temp at which the enzymes have the maximum rate of enzyme acticity
what are buffer solutions
solution that resist changes in pH by donating and accepting H+ ions e.g haemoglobin
what is the excess effect of temperature on enzymes
breaks hydrogen bonding holding tertiary structure.
does priomary structure of enzyme change by increase/decrease in tmeperature
no, peptide binds aren’t affected
what is the effect of temperature on enzymes
causes molecules to move faster; increases rate of collision & force with which they collide
what is the temperature coefficient
the temperature coefficient of a reaction measure of how much the rate of reactions increases with a 10C rise in temperature.
what is the effect of increasing substrate concentration BEFORE MAXIMUM RATE
increase in frequency of collusuons = more ES complexes are made = more product formed
what is the effect of increasing substrate concentration AFTER MAXIMUM RATE
when all active sites are occupied & ES complexes are made as fast as possible. At this point ENZYME concentration is limiting factor
what is the effect of increasing enzyme concentration BEFORE MAXIMUM RATE
increase in frequency of collusuons = more ES complexes are made = more product formed
what is the effect of increasing enzyme concentration AFTER MAXIMUM RATE
all subrate molecules will be occupying an active site & extra enzymes will have empty active sites. At this point SUBSTARTE conrecnteation is limiting factor
what does enzyme concentration in a cell depend on of a specicif enzyme(2)
rate of synthesis (1) and rate of enzyme degradation (2). (Controlled by coding genes & whether they are on or off.)
thw inital reaction rate is the ___ reaction rate for an enzyme
thw inital reaction rate is the MAXIMUM reaction rate for an enzyme
what are prosthetic groups
non-protein component (1) that forms a permanent part (2)of a functioning protein molecule (3)
are prosthetic groups tempeoraily bound, or permanelty bond to enzyme or can ethy be either?
permanelty bound to enzyme
give an example of a prosethic group & for the enzyme it’s binded to
Zn2+ ion bound to carbonic anhydrase found in red blood cells.
What is carbonic anhydrase
a protein with a prosthetic group (1) found in red blood cells (2) catalyses CO2 + H2O reaction into carbonic acid
what is a cofactor
a substance that has to be present in an enzyme-catalysed reaction for it to take place at an appropriate rate.
How does a cofactor ease enzyme-substrate complex formation(2)
joins with the substrate to form the correct shape for the active site (1)
change charge distributions on enzyme/substrate surface = easier for enzyme & substate to form temporary bonds
what is a coenzyme?
small organic (1) non-protein molecule (2) that binds temporarily to active site of enzymes (3)
True or False coenzymes are used up in reactions with enzymes? if not what happens instead?
false; coenzymes are chemically changed during reaction and need to be recycled to orginal state by another enzyme
which of these are derived from water-solublevitamins: prosthetic group, coenzyme, cofactor?
coenzyme
give an example of coenzyme and where it is derived from? if there’s a deficiency of this vitamin what happens
NAD and NADP come from water-soluble vitamin Nicotinamide B3; deficieny causes pellagra
what is a competitve inhibitor
has a similar shape to substrate (1) and competes for COMPLEMENTARY enzymes active site
what impact does a competitive inhibitor have on the rate of reaction and why?
decreases activity of enzyme; by blocking the active site (1) preventing ES complexes from forming (2)
for which of these does an increase in substrate concentration NOT cause ‘inhibitor rate’ to increase: competitive inhibitors or non-competitive inhibitors
non-competitive inhibitors (see graph)
what is the competitive inhibitor called if it binds irreversibly to enzyme?
inactivator - only happens with few inhibitors
how soes a comeptitve inhibitor work?
reduces rate of ES compelxes formation (1) forms an ENZYME-INHIBITOR complex that s CATALYCTICALLY INACTIVE
true or false most competitve inhibitors reactions with enzymes are reversuble
true
example of comepeitve inhibitor & for what?
statins are competitive inhibitors for cholesterol synthesis
defintiton of non-competitive inhibition (4)
attaches to the ALLOSTERIC site of an enzyme (1)which causes the shape of its actiev site to change (2) by disrputing its tertiary structure (3) hence ES complex can no longer form (4)
true or false non compeittive inhibitors all bind reversibly to enzyme
false some bind reversibly some bind irreversily
give 2 example of a non-competitive inhibition
organophosphates in insecticides and herbicides irreversibly inhibit enzyme acetyl cholinesterase; used in nerve impulse transmission
ATP production in respiration
precursor definition
enzymes which must be activated to catalyze reactions.(1) Another enzyme removes part of the molecule allowing the active site to assume the correct shape
what is the point of precursor enzymes
they are mainly digestive enzymes so they don’t digest any of the cells molecules; must be activated first
give an 2 examples of precursoes and what they are ‘activated’ to become
trypsinogen —> trypsin
pepsinogen —>pepsin
end-product inhibition
the product of a reaction inhibits the enzyme recquires for the reaction (1) by negative feedback loop (2) to control metabolic pathways (3)
what are the advantages of having an end product inhibition system?
multi-enzyme complexes increases efficiency, without increasing substrate concentration
how does end product inhibition sytem improve efficiency
keeps enzyme & substrate in the same area = reduces diffusion time
name an example of an enzyme inhibitor poison
cyanide
how is cyanide poisonous?
when hydrolysed, dissociates into CN- and H+ ions, (1) CN-binds irreversibly to an enzyme in mitochondria to inhibit aerobic respiration (2)
name an example of a medical drug enzyme inhibitor
aspirin
what does aspirin do?
aspirin reduces inflammation, blood clots in b.vesssels & strokes, by preventing hyper cell signalling from damages/infected tissue cells.
how does aspirin work?
aspirin hydrolyses into salicyclic acid, which binds to PROSTAGLANDINS enzyme & changes its shape; PROSTAGLANDINS are cell signalling molecules produced when by damaged/infected tissue cells
what is the difference ebtween venom and poisons
venom - injected into victim (e.g snake bite)
posions - injested toxins
what is anabolism
anabolism is building of molecules
catabolism definition
breaking down of molecuels
how does anabolism and catabolism relate to metabolism
metabolism is the sum of all reactions; including anabolism and catabolism
definition of a model e.g induced fit model
simple / easy to understand (1); representation (1)
Is the Induced fit active site complementary to substrate
NO, it is flexible, changes shape as substrate binds for a closer fit
why do models change over time (4)
Idea of improved technology (1); idea of continually investigated (1); more evidence (1); more accurate representation (1)
explain denatured (4)
R-GROUP INTERACTIONS are disrupted (1); change in tertiary structure (1); change in 3D shape of active
site preventing binding with substrate (1).
True or false enzymes denature at extreme low temperatures to their optimum
false; low temperatures causes slower rate of enzyme activity
why will increasing substrate concentration not affect Vmax when non-competitive inhibitor is present
Inhibitor will always be present (1); some enzymes always inhibited (1).
what is Vmax
the fastest rate of reaction for an enzyme
difference between coenzyme and prosthetic group
coenzyme binds temporarily, prosthetic is a permanent part of the enzyme
