enzymes Flashcards
what are enzymes
protein in the tertiary structure (location of the bonds is determined by the primary structure) which catalyse reactions by lowering the activation energy of the reactions hey catalyse
describe the induced fit model
initially substrate and active site aren’t complementary
as the substrates binds, active site changes shape and moulds around
= strain and tension on the bonds
= less energy needed to break the bonds (lowered activation energy)
how does temperature effect enzymes
lower temp = molecules have less kinetic energy and have less successful collisions
= fewer enzyme - substrate complexes formed
- above the optimum (high enzyme denaturing) , so much kinetic energy, some of the bonds break (hydrogen)
- protein loses unique 3D shape, active site changes shape
= enzyme - substrate complexes form = reduced rate
how does pH affect enzymes
either side of the optimum (below or above) there is rapid denaturing of enzyme
- either too high or too low pH interfere with charges in amino acids
- hydrogen/ ionic bonds break = loss of tertiary structure = active site changes shape
= enzyme denatures and fewer enzyme- substrate complexes
= rate decreases
how does substrate and enzyme concentration effect the rate of enzyme activity
insufficient substrates
fewer collision between enzymes and substrates
lower rate
more substrates but no extra enzymes
active sites all in use
reaction can’t go faster and remains constant
insufficient enzyme
active site become saturated with substrate
rate will stay low
adding more enzymes the rate will increase
if too many enzymes added there is a surplus of enzymes with no substrate to bind to and rate wont increase further
what is the role of a competitive inhibitor and what happens if substrate concentration is increased
same shape as the substrate
bind to the active site
prevents enzyme substrate complexes
if add more substrate, eventually can out- compete inhibitor and no longer has an effect
what is the role of non- competitive inhibitor and what happens if substrate concentration is increased
binds to the allosteric site
causes the active site to change shape
no enzyme- substrate complexes
substate can no longer bind (no longer complementary to active site)
adding more substrate won’t have an effect
what is the biochemical test for starch
add iodine
positive = orange to blue black
what is the biochemical test for reducing sugars
add benedict’s reagent and heat
positive = blue to green, yellow, orange, brick red (indicates conc of reducing sugar)
test for non reducing sugar
following benedict’s test, reagent remains blue
add acid AND BOIL (acid hydrolysis)
cool and neutralise solution (adding alkali)
add benedict’s and heat
positive = blue to orange / brick red (the more red, the higher the concentration of the reducing sugar)
why is the positive result of non reducing sugars only ever orange or brick red
if its non - reducing sugar its probably sucrose (made up of glucose and fructose)
when hydrolysed it goes to 2 sugars instead of one (doubled conc of sugar present
what is the the biochemical test for proteins
biuret
positive = blue to purple
what is the biochemical test for lipids
dissolve sample in ethanol (and shake)
add distilled water
positive = white emulsion forms
