enzymes Flashcards
what is a cofactor?
non-protein component of an enzyme required for activity
what is a prosthetic group?
non-dissociable cofactor
what is a co-enzyme?
dissociable cofactor
what is an apoenzyme?
enzyme without a cofactor
inactive
what is a holoenzyme
enzyme with a cofactor
active
what is heme
enzyme cofactor
porphyrin ring with iron
what are the precursors of cofactors and coenzymes?
vitamins
what does a lack of B1 cause?
Beriberi
what does a lack of vitamin B3 cause?
pellagra
what are proenzymes?
inactive form of enzymes
how are proenzymes activated?
proteolytic conversion which is irreversible
what are common proenzymes?
digestive enzymes
blood clotting enzymes
developmental enzymes
what is the prefix of proenzymes?
-ogen
what is chymotripsinogen?
proenzyme synthesised in the pancreas
activated by cleaving peptide bonds
how is chymotripsinogen activated?
trypsin cleaves bonds to remove a dipeptide (14 and 15)
another dipeptide 147 and 148 are removed
forms A-chymotrypsin which are three chains interconnected by disulphide bonds
what is the michaelis-menten equation?
explains the relationship between rate of reaction and substrate concentration
V0 = Vmax[S]/Km + S
what is the michaelis constant?
substrate concentration when the reaction rate is half of Vmax
what does the michaelis constant show?
a measure of enzyme activity
what does a high michaelis constant show?
enzyme has a low affinity for the substrate - lots is needed for it to reach Vmax/2`
what are isoenzymes?
different forms of one enzyme catalysing the same reaction (but in different tissues)
give an example of an isoenzyme
lactate dehydrogenase
name methods that energy can be stored and released
ATP phosphocreatinine other nucleotides - GTP carbohydrates and glycogen fat
describe the structure of ATP
ribose
adenine
three phosphates
how is phosphocreatine made?
phosphorylation of creatine using ATP catalysed by creatine kinase
what are the uses of biological energy?
transport
motility
anabolism
heat
what is an absolute enzyme?
catalyses one type of reaction for a single substrate
what is a group enzyme?
catalyses one type of reaction for a group of substrates
what is a linkage enzyme?
catalyses one type of reaction for a specific type of bond
what do oxidoreductases do?
oxidation and reduction reactions
what do transferases do?
transfer of functional groups
what do hydrolases do?
hydrolysis
what do lyases do?
add/remove groups from double bond without oxidation or reduction
what do isomerases do?
rearrange atoms to form isomers
what do ligases do?
bond molecules using ATP
how is trypsinogen stored?
acinar cells
where is chymotrypsinogen cleaved?
in the duodenum
what is the reaction rate V?
no of reactions/second catalysed per molecule of the enzyme
what is malonate?
competitive reversible inhibitor of succinate dehydrogenase
what is irreversible inhibition?
an irreversible inhibitor destroys enzyme activity, usually by bonding with side-chain groups in the active site
what is a non-competitve inhibitor?
has a structure different to the substrate
binds to somewhere that isnt the active site and changes the shape of the active site so the substrate cant bind
what is an uncompetitive inhibitor?
has a shape different to the substrate
binds to the ES complex so less product is formed and the ES dissociates slowly
