Proteins: Enzymes Flashcards
(16 cards)
What are enzymes?
- tertiary proteins that lower activation energy of the reaction it catalyses, + so speeds up reaction
- they catalyse a wide range of intercellular + extracellular reactions, that determine structures + functions from cellular to whole-organism lvl
What are the 2 models of enzyme action?
- lock + key model
- induced fit model (accepted model)
Describe the lock + key model of enzyme action.
- substrate fits into an enzyme in same way a key fits into a lock
- model suggests enzyme is rigid + its active site is a fixed shape, + bc of random collisions, substrate can collide + attach to enzyme to form an enzyme-substrate complex
- charged groups within active site are then thought to distort substrate, lowering activation energy
Describe the induced fit model of enzyme action.
- suggests enzyme is flexible, + when it collides w a substrate, to form an enzyme-substrate complex, the active site undergoes conformational changes to mould around substrate
- this puts a strain on bonds in substrate, lowering activation energy
- products are then removed, + enzyme’s active site returns to its original shape
What do properties of an enzyme relate to?
- tertiary structure of its active site + its ability to combine w complementary substrates to form an enzyme-substrate complex
Describe the specificity of enzymes.
- have a specific + unique active site bc of specific folding + bonding in tertiary structure of protein
- this means enzymes can only bind to specific, complementary substrates, to form enzyme-substrate complexes
What are the 2 types of enzyme reactions?
- catabolic: when substrate binds to active site, it puts a strain on bonds in substrate, causing it to break down more easily
- anabolic: when substrates bind to active site, it holds them close together + dec repulsion, so can bond more easily
What factors affect the rate of enzyme controlled reactions?
- T°C
- pH
- substrate conc
- enzyme conc
- inhibitors
Describe how T°C affects the rate of enzyme controlled reactions.
- if T°C is too low, there’s not enough KE for successful collisions between enzymes + substrates, so less enzyme-substrate complexes form
- if T°C is too high, H + ionic bonds holding tertiary structure in shape break, + so enzyme active site changes shape
- means enzyme-substrate complexes can’t form, + so enzymes denature
Describe how pH affects the rate of enzyme controlled reactions.
- if pH is too high or too low, it will interfere w charges of AAs in active site
- this can break H + ionic bonds holding tertiary structure in shape, so active site changes shape meaning fewer enzyme-substrate complexes form + enzyme denatures
- diff enzymes have a diff optimal pH
Describe how substrate conc affects the rate of enzyme controlled reactions.
- insufficient substrate leads to fewer collisions between enzyme + substrate, so fewer enzyme-substrate complexes form, causing ROR to dec
Describe how enzyme conc affects the rate of enzyme controlled reactions.
- insufficient enzymes lead to active sites becoming saturated w substrate, + so are unable to work any faster
What are the 2 types of enzyme inhibitors?
- competitive inhibitors
- non-competitive inhibitors
Describe how competitive inhibitors affects the rate of enzyme controlled reactions.
- have similar shape to substrate, so can bind to enzyme’s active site + prevent substrate from binding, slowing down enzyme activity
- if more substrate is added, it will out-compete inhibitor, knocking them out of active site
Describe how non-competitive inhibitors affects the rate of enzyme controlled reactions.
- bind to an allosteric site of enzyme (site away from active site), which causes active site to undergo conformational changes
- this means substrate is no longer complementary, + so can no longer bind to enzyme’s active site, stopping enzyme activity
How do you calculate pH?
- pH = -log10[H+]
