OCR A-level Biology- enzymes

what is an enzyme

a globular protein that interacts with substrate molecules to increase the rate of reaction

what type of catalyst is an enzyme

a biological catalyst

what is a catalyst

a chemical that speeds up the rate of reaction without being used up

what is a catabolic reaction

a reaction that breaks a substance down

what is an anabolic reaction

a reaction that builds something

what is an intracellular enzyme

enzymes present inside the cell membrane

what reaction does catalase catalyse

the decomposition of hydrogen peroxide into water and oxygen

what type of enzyme is catalase

catalase is an intracellular enzyme

what type of enzyme is amylase/trypsin

amylase and trypsin are extracellular enzymes

what is an extracellular enzyme

extracellular enzymes catalyse reactions that occur outside of cells

what does amylase do and where is it found

amylase is found in the pancreas and salivary glands and is involved in the digestion of maltose into glucose

what does trypsin do and where is it found

trypsin is found in the small intestine and is involved in the digestion of protein molecules

wat is the temperature coefficient (Q10)

the rate of change of a biological/chemical system as a consequence of increasing the temperature by 10 degrees

what does increasing the temperature do to the rate of reaction

it increases the rate of reaction up to the optimum temperature and then beyond the optimum temperature it decreases the rate of reaction

why does increasing the temperature increase the rate of reaction

increasing the temperature increases the kinetic energy of each molecule increasing the likelihood of more successful collisions

what effect does increasing the pH have on the rate of reaction

up to the optimum pH increasing the pH increases the rate of reaction, but beyond the optimum pH increasing the pH decreases the rate of reaction

what effect does increasing enzyme concentration have on the rate of reaction

increasing enzyme concentration increases the rate of reaction up to vmax and beyond vmax has no effect as the rate of reaction plateaus

what effect does increasing substrate concentration have on the rate of reaction

increasing substrate concentration up to vmax increases the rate of reaction but beyond vmax it has no effect as the rate of reaction plateaus

what does it mean when an enzyme denatures

denaturing is when the bonds within the tertiary structure break causing the shape of the active site to change which affect the enzme’s ability to form enzyme-substrate complexes

what is renaturation of an enzyme

when the pH returns back to the optimum the bonds within the tertiary structure reform allowing the shape of the active site to become complimentary to the substrate again

when can renaturation occur

when the pH does not significantly deviate from the optimum

what is vmxax

the highest theoretical rate of reaction under specific conditions

what is enzyme inhibition

when an enzyme is prevented from forming enzyme-substrate complexes

how does a competitive inhibitor inhibit enzyme activity

competitive inhibitors have similar shapes to the active site allowing them to temporarily bond to the enzyme preventing enzyme-substrate complexes forming

how does a non-competitive inhibitor inhibit enzyme activity

non-competitive inhibitors bind to the allosteric site of an enzyme altering the bonds within the tertiary structure, changing the shape of the active site preventing enyme-substrate complexes from forming

does competitive inhibition affect vmax

no because if the substrate concentration was high enough then the substrate molecules will outcompete the inhibitors

does non-competitive inhibition affect vmax

non-competitive inhibitors cause changes in the active site so increasing the substrate concentration wouldn’t change the rate of reaction as enzyme-substrate complexes can’t form

what does a competitive inhibitor form when it bonds to an enzyme

an enzyme-inhibitor complex

what is a competitive inhibitor that binds irreversibly called

an inactivator

what is reversible inhibition

when an inhibitor temporarily combines with an enzyme which is reversed when the inhibitor is no longer attached to the enzyme

what is irreversible inhibition

when an inhibitor permanently combines with an enzyme inactivating it

what is end product inhibition

when the product of an enzyme acts as inhibitor to the enzyme that produced it

why is end product inhibition useful

to prevent the formation of excess product

what kind of molecule are cofactors

inorganic

what kind of molecule are coenzymes

organic

what is a cofactor

a substance made from amino acids that is required by an enzyme to function (they can be temporary or permenant)

how do cofactors aid reactions

they help the enzyme and substrate bind together but aren’t used up/don’t participate in the reaction

what is a coenzyme

a small organic, non-protein cofactor involved in enzyme-catalysed reactions by donating or accepting hydrogen/chemical groups

how does a coenzyme aid reactions

they participate in the reaction often acting as carriers

what is a prosthetic group

a cofactor bound tightly to an enzyme

what is an apoenzyme

a precursor enzyme before the cofactor is added

what is a haloenzyme

an activated enzyme with a cofactor

what is a proenzyme/zymogen

when a change in environment causes a change in the tertiary structure of a precursor enzyme

what is an inactive precursor enzyme

where enymes that could cause damage to cells/tissues releasing them so are inactive

how are precursor enzymes activated

through a change in shape/change to the tertiary structure

what is the lock and key theory

the idea that an enzyme’s active site matches exact with one type of substrate

what is it called when an enzyme bonds to a substrate

an enzyme-substrate complex

what is the induced fit hypothesis

the idea that as an enzyme and substrate approach one or both of the molecules change shape slightly to fit together perfectly