Enzymes Flashcards
what kind of proteins are enzymes
globular
what is an anabolic and catabolic reaction
anabolic – chemical reactions required for growth
catabolic – breaking down reactions
define metabolism
sum of all different reactions and reaction pathways happening in a cell or organism
Define Vmax
enzymes can only increase the rate up to a certain point
Define specificity
Each enzymes catalyses a different biochemical reaction
Define the lock and key hypothesis
Only a specific substrate will fit into the active site of an enzyme
When bound, an ESC forms
Substrate reacts forming an EPC
The products are released
define the induced fit hypothesis
active site changes slightly as the substrate enters the active site
initial interaction between substrate and enzyme induces changes in the enzyme’s tertiary structure
that strengthen binding and weakens the bonds in the substrate
lowering the activation energy
what is an intracellular enzyme and extracellular enzyme
give examples
intra – act within cells
> hydrogen peroxide broken down to oxygen and water by catalase
extra – work outside the cell that secreted them
> amylase and trypsin
define the temperature coefficient
measure of how much the rate increases with a 10 degree rise in temperature
how does denaturation occur when the temperature goes above optimum
vibration of bonds causes strain then breaking of bonds
causing a change in the tertiary structure of protein
so it is no longer functional as it is no longer complementary to its substrate
compare enzymes that are adapted to cold environments to enzymes adapted to hot environments
cold – have flexible structures which make them less stable (small temp changes denature them)
hot – have more sulfur bridges and hydrogen bonds so more stable
(makes them more resistant to temp change)
define renaturation
pH returns to optimum which means the protein can resume its original shape and function properly
what causes changes in protein structure when the pH changes (low and high)
low – less R-groups interact with each other causing bond breaking
high – more R-groups interact with each other, more bonds are formed
explain substrate and enzyme saturation
more substrate –> higher collision rate with active sites and formation of more ESC, higher rate
more enzymes –> more active sites available so more ESC, so higher rate
when substrate saturation occurs, what can increase the rate
temperature
why shouldn’t reactions happen too quickly in organisms
could lead to build-up of excess products and waste of resources
define an inhibitor
molecule that prevents an enzyme from carrying out its function
define competitive inhibition
molecule binds to active site to block the substrate
prevents ESC
substrate and inhibitor compete to bind to the active site
their effect is reversible
what does the degree of competitive inhibition depend on
relative conc of the enzyme, substrate and inhibitor
how does competitive inhibitors affect the rate and the Vmax
reduces the rate
Vmax stays the same
define non-competitive inhibition
molecule binds to allosteric site
cause change in enzyme’s active site
enzyme becomes non-complementary
how does increase the concentration of the enzyme affect the effect of the non-competitive inhibitor
doesn’t overcome the effect of the non-competitive inhibitor
define end-product inhibition
when the product inhibits its enzyme
> negative feedback
prevents waste of resources
(non-competitive reversible inhibition)
define a cofactor and coenzyme
component of an enzyme required for it to function
cofactor – inorganic, come from diet
coenzyme – organic, come from vitamins
define a prosthetic group
permanently bound to their enzyme
required for the enzyme to function
define precursor activation
enzymes produced in inactive form because it causes damage when it released
how does the precursor enzyme become activated
addition of a cofactor cause change in their tertiary structure
what is apoenzyme and what does it become when a coenzyme is added to it
precursor protein
becomes holoenzyme
define a proenzymes/zymogens
change in the tertiary structure (activation of enzyme) brought about by the action of another enzyme or the changes in conditions
are globular proteins hydrophilic or hydrophoboc on the outside
hydrophilic
