enzymes Flashcards
what are enzymes
Enzymes are tertiary structure proteins that catalyse reactions. The chemical reactants that enzymes bind to are called substrates.
how do they act as biological catalysts
they lower the activation energy of a reaction
why are enzymes highly specific
because enzymes are made of a single polypeptide chain they have a tertiary structure
their tertiary structure is determined by their primary structure. as the sequence of amino acids causes bonds to form in different places which causes the protein to coil or fold in different ways
which leads to a specific shaped enzyme with a specific shaped active site
so therefore many enzymes can only catalyse one reaction
how can the active site change shape
changes in PH or TEMP which alters the tertiary structure which causes a change in the shape of the protein
mutation- because the primary structure is determined by a gene
if a mutation occurs in that gene it could cause a change in shape as it could lead to a alteration in the primary structure which would lead to an alteration in tertiary structure which would lead to a change in shape
induced fit vs lock and key
lock and key- substrate and active site are completely complementary before they meet so the substrate fits into the enzymes active site just as a key would into the lock
induced fit- unlike lock and key the substrate and enzymes active site are not completely complementary before they join
only when the substrate enters the active site and the active site is induced (changes shape slightly) do the substrate and active site become completely complementary.
in both cases when the substrate enters the active site an ENZYME-SUBSTRATE COMPLEX is formed (this is what lowers the activation energy and enables enzymes to be biological catylysts)
how does an enzyme lower the activation energy
it happens when the substate enters the enzymes active site and forms an enzyme-substrate complex:
this lowers AE because:
-the joining of the substate to the active site puts a STRAIN on the bonds in the substrate therefore meaning less energy is required to break them and this energy is provided as heat so therefore less heat required therefore lowering AE
what is the name given to enzymes that work inside cells and enzymes that work outside cells
inside- intracellular
outside-extracellular
what is the substrate
whatever is being reacted
could be splitting up substrate or joining
if you have a fixed number of enzymes and a constantly increasing concentration level of substrate why does the rate of reaction level out at some point
because you have a set number of enzymes they become the limiting factor as the rate of reaction is limited to how many enzymes can form enzyme substrate complex’s with substrates at any one time. and this is limited to how many enzymes there actually are
active sites will become fully saturated (full of substrate) so there will be a constant rate of reaction limited by the amount of enzymes
this is called SATURATION POINT
how does changing PH cause enzyme to denature
Changing pH changes the number of hydroxide ions and hydrogen ions surrounding the enzyme. The ions can alter the hydrogen and ionic bonds between amino acids.
ACID- h+
ALKALINE- OH-
competitive and non-competitive inhibitors
Reaction rate is influenced by the presence of competitive and non-competitive inhibitors.
competitive- competes to bind to enzymes active site to form inhibitor-enzyme substrate and blocks the substrate so rate decreases (combat this by increasing the conc of substrate you want to join to active site.
non competitive- join to enzyme at a site other than the active site, this causes the active site to change shape so it is no longer complementary to the substate
