cc4 - enzymes Flashcards
metabolism
sum of all the enzyme controlled chemical reactions taking place in a cell
2 main types of reactions that make up metabolism
anabolic
catabolic
anabolism
set of metabolic pathways that synthesise complex molecules from smaller, simpler ,molecules
catabolism
set of metabolic pathways that breakdown complex molecules into smaller, simple molecule
enzyme
biological catalyst used to speed up rate of intracellular + extracellular biochemical reactions
not used up or permanently altered
intracellular enzyme
enzyme that acts within cells
e.g: catalase
extracellular enzyme
enzyme secreted by cells + functions outside of cells
e.g: amylase
active site of enzyme
region of enzyme that is complementary to shape of a specific substrate
substrate binds + reaction takes place
why is active site described as specific
3D structure of each enzyme (including active site) is unique due to presence of different side chains + branches
only specific substrates complementary to active site can bind
activation energy
minimum amount of energy required for a reaction to take place
catalysis
increase in rate of chemical reaction using a catalyst (such as an enzyme)
catalyst lowers activation energy of reaction
lock and key model
- substrate + active site of enzyme come into contact
- substrate binds, enzyme-substrate complex forms
- reaction takes place, products formed in enzyme-product complex
- products released from active site
active site now free to bind to another substrate
induced fit hypothesis
model of enzyme action stating that once a specific substrate binds to active site, enzyme undergoes subtle conformational changes
puts strain on substrate, lowering activation energy for reaction
factors affecting rate of enzyme-controlled reaction
temperature
pH
substrate concentration
enzyme concentration
how temperature affects rate of enzyme-controlled reactions
as temp increases, molecules have more kinetic energy
molecules moved faster + collide more frequently
more ES complexes form
tate of reaction increases
rate peaks at optimum temperature
how increasing temp above optimum affects rate of enzyme-controlled reaction
increased vibration break H + ionic bonds in tertiary structure
active site changes shape, enzyme is denatured
no more ES complexes form
rate of reaction decreases
how pH affects rate of enzyme-controlled reactions
enzymes have optimum pH
pH shifts from optimum
H + ionic bonds in tertiary structure are altered
interaction of polar + charged R groups changes
active site changes shape, enzyme is denatured
rate of reaction decreases
buffer
molecules maintaining constant pH in a solution when small volumes of acid (H+) or base (OH-) are added
how substrate concentration affects rate of enzyme-controlled reaction
if enzyme concentration is fixed, rate of reaction increases proportionally to substrate concentration
once all active sites are full, rate of reaction remains constant (graph plateaus)
enzyme concentration is limiting factor
how enzyme concentration affects rate of enzyme-controlled reaction
if substrate concentration is fixed, rate of reaction increases proportionally to enzyme concentration
when all substrates occupy active sites, rate of reaction plateaus (substrate concentration is limiting factor)
competitive inhibitor
molecule which competed for active site of enzyme, blocking it + preventing substrate from binding
is competitive inhibition temp or permanent
generally temp
some cases (e.g: aspirin) may be permanent
how increasing substrate concentration affects competitive inhibition
increase in substrate concentration
more substrate than inhibitor
rate of reaction increases
non-competitive inhibitor
inhibitor binds to different part of enzyme (allosteric site)
tertiary structure of enzyme (including active site) changes shape
active site no longer complementary to substrate
substrate can’t bind + enzyme is inhibited
is non-competitive inhibition temp or permanent
permanent
how increasing substrate concentration affects non-competitive inhibition
won’t overcome effect of non-competitive inhibitor
immobilised enzymes
enzymes attached to inert, insoluble material over which substrate passes + reaction takes place
example of application of immobilised enzyme
biosensors
why immobilised enzymes important in industrial processes
enable enzymes to be reused
improves enzyme stability in variable/extreme temps + pHs
increases efficiency of reactions
