ENZYMES Flashcards
Enzymes
enzmes are tertiary structure of protein that acts as a biological catalyst
all enzymes are?
globular proteins
how does an enzyme work?
an enzyme works by lowering the activation energy
activation energy
the minimum energy which is required to start a chemical reaction is called an activation energy.
substrate
substrate is the substance in which the enzyme can react on.
active site
active site is an area of the enzyme where the substrates bind.
why is active site in enzyme unique
because of the specific folds and bonding in the tertiary structures of protein .
co factors
non protein groups which are essential for the functioning of an enzyme.
co factors?
prosthetic groups & co enzymes and activators
prosthetic group
nom protein group which could be organic or inorganic. they form a permanent attatchment to the enzyme. iron in haem group. haem is also present in an enzyme called catalase.
co enzymes
organic which are mostly derived from vitamins. eg NAD+ ( NICOTINAMIDE ADENINE DINUCLEOTIDE) is derived from vitamin B3.
ACTIVATORS
inorganic ions. eg magnesium calcium zinc etc
hypothesis in enzymes
- lock and key hypothesis
- induced fit hypothesis
lock and key hypothesis
- suggests that the active site and enzyme substrate have complementary shapes so they fit together and form an enzyme substrate complex.
- because of the shape of the active site only one type of substrate can bind with the enzyme. enzymes are therefore said to be specific.
- once the esc are formed, within the active site are thought to distort the substance and lowers the activation energy. products are now released and active site is now empty and ready to be used.
induced fit hypothesis
- modified form of lock and key hypothesis
- hands and glove
- suggests that the active site in an enzyme is slightly induced or changed to form an enzyme substrate complex. when the enzyme substrate complex is formed due to the molding of enzyme around the substrate, it puts strain on the bonds and lowers the activation energy.
- product is then removed and enzymes active site comes back to its original shape.
factors affecting the enzyme
- enzyme concentration
- substrate concemtration
- temperature
4.pH
ENZYME CONCENTRATION
there is a direct co relation between enzyme concentration and rate of reaction. as the enzyme conc increases, more activesites are available for the substrate to bind - more collisions - more product.
substrate concentration
as the substrate conc is low, active sites are not fully utilised. as the substrate concentration increases, more active sites are utilised but there comes a point where all the active sites will be fully utilised and the enzyme wont work faster.
temperature
increase intemperature - increase in kinetic energy - increased collisions between substrate and enzyme - more produts are formed - increases rate of rxn.
enzymes have an optimum temp of 40 c. if temp goes beyond , it causes denaturation of enzymes which means change in active site and shape which slows down the reaction as no substrates can bind.
high temp - additional kinetic energy - intramolecular vibrations betweeen weak hydrogen bonds holding polypeptide chains
pH
- Too high or too low ph interferes with changes in amino acids in active sites which can break bonds holding tertiary structures in protein.
inhibitors
certain substances that inhibits the activity of enzymes.
types of inhibitors
competitive inhibitor and non competitive inhibitors
competitive inhibitors
same shape as the substrate. substrate and inhibitor compete to bind to the active site. since inhibitors have similar characteristics to that of substrate, it binds to the active site preventing the substrate from binding.
non competitive inhibitor
inhibitor doesnt bind to the active site, but binds to an allosteric site causing the active site to change shape and substrate can no longer bind.
