Enzymes Flashcards
give an example of an extracellular enzyme
amylase, secreted by mouth cells and catalyses hydrolysis of starch
give an example of an intracellular enzyme
catalyses, breaks down hydrogen peroxide
what type of proteins are enzymes
globular
what is the active site
the part of the enzyme where the substrate molecules bind
the active site shape is determined by what
tertiary structure
what is it called when a substrate binds to an active site
enzyme-substrate complex
how do enzymes speed up reactions
reduce the activation energy
what are the two reasons for why the formation of an enzyme-substrate complex lowers activation energy
-if two substrates need to be joined, attaching to the enzyme holds them close together so there is less repulsion and can bond more easily
- in a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate so it can break down more easily
describe the lock and key model
the idea that the substrate fits into the enzyme as they have the exact complementary shape
describe the induced fit model
the substrate has to have the right shape to bind to the active site but also has to change the shape of the active site
how does temperature affect enzyme activity
if temperature is too high, molecules vibrate more causing to break bonds that hold enzyme shape and the active site will change shape and become denatured
if temperature is too low then the number of successful collisions will reduce due to lack of kinetic energy
what is the temperature at which the rate of an enzyme controlled reaction is at its fastest
optimum temperature
what is the equation for temperature coefficient
Q10= R2 (rate at higher temperature)/ R1 (rate at lower temperature
How does pH affect enzyme activity
the H+ ions and OH- ions produced above and below optimum pH, can break the ionic bonds in the tertiary structure, causing Mayme to denature
what enzyme works best at pH two and is found in stomach
pepsin
how does enzyme conc affect enzyme activity
the more enzyme molecules in a solution the more likely there is for a collision to occur with a substrate molecule
however if substrate is limited there comes a point where adding further enzyme has no further affect
what is the effect of substrate conc on enzyme activity
the higher the substrate conc, the faster the reaction, more likely for collisions to occur, only true up to a saturation point where enzyme conc becomes the limiting factor
substrate conc also decreases over tike during a reaction so if no other substrate is added then the speed of reaction will also decrease over time
what is a cofactor
a non protein substance that binds to an enzyme to help it function
what is an inorganic cofactor
help substrate and enzyme bind but don’t participate directly so aren’t used up or changed in any way
what are organic cofactors called and how do they aid enzyme function
coenzymes, participate in reaction and often act as carriers by moving chemical groups between different enzymes
what are competitive inhibitors
molecules that have the same shape as substrate molecules, block active site so substrate cannot bind, high conc of inhibitor means most active sits will be take up, however if there is a higher conc of substrate than the chance of it reaching an active site before the inhibitor is high
what are non-competitive inhibitors
bind to enzyme away from the active site and to the allosteric site, changing active site shape so substrate molecules can no longer bind
what type of drugs act as enzyme inhibitors
antiviral drugs, prevent replication of DNA
antibiotics
what metabolic potions act as enzyme inhibitors
cyanide- non competitive, irreversible
malonate- competitive
arsenic- non competitive
what is a prosthetic group and give an example
a cofactor tightly bound to an enzyme- Zn2+ for carbonic anhydrase
what nutrition group is often a source of coenzymes
vitamins
what is the cofactor for amylase
chloride ion
what is end product inhibitor and what do they regulate
metabolic pathways are regulated by end-product inhibition, a metabolic pathway isa series of metabolic reactions, the product of the first takes part in the second reaction and so on, each reaction uses a different enzyme, many enzymes are inhibited by the product of the reaction they catalyse, the final product in the metabolic pathway inhibits an enzyme that acts easier on in the pathway
