what are enzymes?
biological catalyst that accelerates the rate of chemical reaction in cells
type of protein
specificity of enzyme
enzymes may only catalyse one specific reaction
eg. reaction involves particular chemical bond or functional group
active site
specific part of the enzyme molecule that has a unique shaped cavity within the protein structure (determined by its tertiary structure) where the reaction occurs
substrate
reactant that reacts with the active site of an enzyme
enzyme-substrate complex
substrate fits into the enzyme like a key to a lock and allows enzyme to break the bonds in the substrate.
each enzyme is specific to a particular substrate so other molecules will not cause a reaction
how do enzymes speed up rate of reaction?
when the substrate bonds to the enzymes active site, the bonds in the substrate weaken and the reaction can occur with lower activation energy
enzyme inhibitors
block undesirable reactions utilising the understanding of enzyme mechanisms
competitive inhibitors
mimic substrate and compete for the enzyme active site
prevents enzyme from catalysing harmful reaction
what influences effectiveness of competitive inhibitor
relative concentrations of the inhibitor and the natural substrate
non-competitive inhibitors
bond to a different part of the enzyme
alters the shape and indirectly impacts the active site
prevents substrate from binding blocking enzymes activity
difference b/w competitive and non-competitive inhibitors?
effectiveness of non-competitive inhibitors are not effected by the concenration of the subsrate
effectiveness of drug is influenced by…
its spatial arrangement especially with chiral molecules (enantiomers)
enzyme activity
rate of conversion of substrate into products by enzyme
amount of substrate that is converted into products per unit time
what is enzyme activity dependant on?
quantity of active enzyme
reaction conditions: pH and temperature
how is enzyme activity measured?
measuring concentration of reactant or products
UV-vis and HPLC
what do the reaction conditions effect?
frequency at which the substrate molectules enter the enzyme active site
effectiveness of the enzyme as a catalyst
effect of pH on enzyme activity
R groups of the amino acid are affected by pH changes which can alter the tertiary structure as a result. As tertiary structre of the enzyme is disrupted, the enzyme’s active site changes shape and enzyme activity decreases.
Drastic changes to pH can result in permanent change to the shape of enzyme (denaturation)
normal pH conditions of enzymes
enzymes operate within a narrow pH range and activity outside this range drops drastically
enzyme optimum pH
pH at which enzyme activity is the greatest
effect of temperature on enzyme activity
above optimum temperature
Increased temperature causes increased kinetic energy of molecules and increased movement throughout the enzyme resulting in breakage of intermolecular forces. This disrupts tertiary and quaternary structures of the ezyme, causing a change in 3D shape of active site, no longer allowing it to effectively catalyse a reaction, reducing the rate of reaction.
effect of temperature on enzyme activity
below optimum temperature
Enzyme and substrate have low kinetic energy, resulting in less frequent, less energetic collisions between molecules.,meaning enzyme activity decreases
enzyme optimum temperature
temperature where enzyme activity is highest (in human body 37 degrees)
higher/lower than optimum temperature impars enzyme functions
denaturation
changein enzyme tertiary structure which causes a change in shape of the active site, and the enzyme loses its catalytic activity
primary structure of the protein stays intact becasue the covalent bonds are too strong to be broken
hydrolysis of proteins
breaking covalent bonds in the peptide link producing shorter polypeptides or individual amino acids
