enzyme action Flashcards
what are enzymes
biological catalysts that speed up metabolic reactions in living organisms by raising activation energy
catalysts remain unchanged at the end of the reaction
small amount can catalyse conversion of large no of substrates into product
turnover number
the number of reactions that an enzyme molecule can catalyse per second
what type of protein is an enzyme
globular protein
soluble in water bc of hydrophilic nature of R groups in their aa
why are enzymes important
to sustain life, chemical reactions must occur rapidly with the aid of enzymes
what is the role of enzymes in anabolic reactions
build up/synthesise large polymers
e.g. cellulose/long protein molecules
catalyses reaction
what is the role of enzymes in catabolic reactions
break down large organic molecules
e.g. disgestion of large organic molecule starch into monomer, release of energy during respiration
catalyses reaction
how does enzyme function
both intra/extraceullarly
example of an intracellular process
dna replication
dna polymerase, ligase
catalse, protects cell from damage by breaking down hydrogen peroxide to water and oxygen
4 polypeptide chains and a haem group, highest turnover number
example of an extracellular process
digestion
amylase, produce in salivary glands, digest starch to maltose
what is a metabolic pathway
series of consecutive reactions with each step being catalysed by a different enzyme, specific to substrate produced
cam be anabolic/catabolic
e.g. respiration, photosyntesis
what happens when one enzyme cannot function
whole metabolic pathway cannot run
what are metabolites
reactants, intermediaries, products
what are oxidoreductases
enzymes that catalyses the transfer of electron during oxidation and reduction reactions
transferases
the transfer of functional group from one molecule to another
hydrolases
catalyses hydrolysis
lyases
splitting of bonds
isomerases
rearranging of molecule
ligases
joining two molecules by forming covalent bonds
general equation for enzyme-controlled reaction
enzyme + substrate –> enzyme-substrate complex –> enzyme product complex –> enzyme
+ product
activation energy
energy to start the reaction
how do enzymes increase the rate of a reaction
activation energy is transferred to break the bonds of reactants
enzyme lowers activation energy by creating a transition state between the enzyme and substrate that is more stable
if 2 substrate molecules need to be joined, attaching to enzyme holds them close together so they can bond more easily
if enzyme is catalysing a breakdown, fitting into active site puts a strain on the bonds in the substrate allowing molecule to break more easily
what maintains the shape of the enzyme and active site
amino acids
how does enzyme form
folding of sequence of amino acids
lock and key hypothesis
substrate fits exactly into active site just like a key fitting a lock
held there with various bonds to form enzyme-substrate complex
1. substrate molecule is split into two or more products
2. more substrate molecules are joined together
complex only exists for a fraction of a second until the products are formed
products leave the active site and enzyme is free to take part in another reaction
induced fit hypothesis
active site initially not an exact fit for the substrate
substrate moves into active site, forces between the two molecules, distort enzyme and active site
enzyme substrate complex forms
formation of complex lowers activation energy to form products
products leave the active site and enzyme return to shape
cofactors
a small non-protein molecule attached to enzymes
two types of cofactors
activators and coenzyme
activators
inorganic groups that permanently bound to the enzyme and prosthetic group
iron zinc copper
coenzymes
large organic molecules that bind temporarily to the enzyme transferring chemical groups that is necessary for reaction to occur
nad
vitamin b3, c
atp
amylase as an example of cofactor
only digest starch if Cl- is present
precursor activation
inactive enzymes
important bc some enzymes causes damage in their activated form
undergo a change in shape to be activated, by addition of a cofactor
precursor protein, apoenzyme before activation
holoenzyme after activation
