enzymes Flashcards
what are enzymes
biological catalysts made of globular proteins which speed up reactions by lowering the activation energy. they are not used up themselves so can be reused
what is the active site
this is the tertiary structure of the enzyme which is a specific, unique complementary shape to the substrate molecules
what is an example of an enzyme catalysing an intracellular reaction ?
catalase is an intracellular enzyme within liver cells which breaks down hydrogen [eroxide into oxygen and water
what is an example of an enzyme involved in an extracellular reaction
trypsin is an extracellular enzyme in the small intensities which breaks down proteins
describe the lock and key model
suggests that the enzyme is a lock and the substrate is a key which fits perfectly into the lock. the enzyme has a tertiary structure the exact complementary shape of the substrate. random collisions cause the substrate and enzyme to collide creating an enzyme substrate complex. the substrate then reacts and the product is formed which creates an enzyme product complex. products then detach from the enzyme and the enzyme can then be reused
what is the induced fit hypothesis?
this suggest the enzyme is like a glove and the substrate is like a hand. they aren’t complementary to eachoveth but the glove wink mould around the hand. the active site is induced/changes slightly to mould around the substrate. this puts strain on bonds and therefore decreases the activation energy so the reaction occurs quicker
how does temperature affect enzyme rate of reaction?
if the temperature is too low then there is little kinetic energy which means there aren’t many collisions, however if the temperature is too high then the enzymes tertiary structure bonds break so the active site changes and the enzyme is denatured
what is the q10 temperature coefficient ?
a measure of the rate of change of an enzyme controlled reaction as a result of increasing the temperature by 10
what is the q10 coefficient equation?
q10 = rate of reaction at x + 10 degrees / rate of reaction at x degrees
how does pH affect enzyme rate of reaction ?
if the pH is too high or too low then the charges in the amino acids will be interfered with in the active site. this causes the bonds to break and the tertiary structure is changed meaning the active site will no longer be complementary to the substrate.
how do the H+ ions interfere with the bonds?
some organic and inorganic acids can donate to proteins when they are dissociating.
Hcl –> H+ + Cl-
The H+ are attracted towards the negative charges, this interferes with the hydrogen bonds and changes the tertiary structure
how does substrate concentration affect enzyme rate of reaction?
if there is a low concentration of the substrate the reaction rate will be lower as there will be fewer collisions occurring. at high concentration the rate will eventually plated as all the enzyme active sites will be saturated and in use
how does enzyme concentration affect enzyme rate of reaction?
if there is a low enzyme concentration there will be a low rate of reaction as there is nothing for the substrate to bind to. if there is a high enzyme concentration then there will be more collisions and more enzyme substrate complexes formed so there is a higher rate of reaction
what are enzyme inhibitors?
these are substances that reduce the activity of an enzyme by combining with an anexyme molecule and effects the enzyme turnover number
what is a competitive inhibitor?
these are the same shape as the complementary substrate which means they cana los bind to the active site in competition with the substrate molecule. this forms an enzyme inhibitor complex
