enzymes Flashcards
what are enzymes?
enzymes are biological catalysts that speed up chemical reactions
what is a catalyst?
a substance that speeds up a chemical reaction without being used up in the reaction itself
give 2 examples of intracellular enzymes
hydrogen peroxide-toxic by product of several cellular reactions
catalase- catalyse the breakdown of hydrogen peroxide to harmless oxygen and water
give 2 examples of extracellular enzymes
amylase- found in saliva, catalyses the hydrolysis of starch into maltose in the mouth
trypsin- catalyses the hydrolysis of peptide bonds, produced by pancreas and secreted into the small intestine
what type of proteins are enzymes
globular proteins
what are the 4 factors that affect enzyme activity?
temperature, PH, Enzyme conc and substrate conc
the equation for temperature Coefficient
Q10=R2(rate at higher temperature)/ R1 (rate at a lower temperature)
what does a temperature coefficient show?
shows how much the rate of a reaction changes when the temperature is raised by 10 degrees
what are cofactors?
non protein substance
what cofactor is used for the enzyme, amylase?
Chloride ions
what are inorganic cofactors
they dont directly participate in the reaction so are not used up or changed in any way
what are organic cofactors called?
coenzymes
what are coenzymes?
they participate in the reaction and are changed by it, they act as carriers, moving chemical groups between different enzymes, they are continually recycled during this process
what is a prosthetic group?
when a cofactor is tightly bound to the enzyme
what is an example of a prosthetic group?
zinc ions are a prosthetic group for carbonic anhydrase, zinc ions are a permanent part of the enzymes active site
what is competitive inhibition?
the inhibitor has a similar shape to the substrate so they compete with the substrate molecules to bind to the active site but no reaction takes place.
what is non competitive inhibition?
inhibitors bind to the enzyme away from its active site, allosteric site. this causes the active site to change shape so the substrate molecules can no longer bind to it
what bonds can make inhibition irreversible
strong covalent bonds between the enzyme and inhibitor
what bonds can make inhibition reversible
weaker hydrogen or weak ionic bonds
name 2 examples of medicinal drugs that are enzyme inhibitors
penicillin inhibits the enzyme transpeptidase which catalyses the formation of proteins in bacterial cell walls
some antiviral drugs
name 2 examples of metabolic poisons that are enzyme inhibitors
cyanide- inhibitor of cytochrome c oxidase, an enzyme that catalyses respiration reactions
malonate inhibits succinate dehydrogenase which also catalyses respiration reactions
why are some enzymes synthesized as inactive precursors?
to prevent them causing damage to cells.
