Enzymes Flashcards
define intracellular
within cells
define extracellular
outside cels
give an example of an intracellular enzyme
catalase - catalases the breakdown of hydrogen peroxide to harmless oxygen and water
give two examples of extracellular enzymes
amylase - catalases hydrolysis of starch
trypsin - catalases hydrolysis of peptide bonds
where is trypsin produced / secreted ?
pancreas / small intestine
All enzymes are … proteins
globular proteins
what happens when a substance binds to an enzyme ?
the enzyme-substrate complex is formed, which lowers the activation energy
If the two substrates must join, what does the enzyme do?
holds them closer, reducing repulsion
If an enzyme is catalysing a breakdown reaction…
fitting into the active site puts strain on the bonds (so breaks up more easily)
explain what happens to enzyme when the temp goes to high
The enzyme’s molecule vibrates too much, breaking some of the bonds, changing the shape of the active site (denatured)
what does the temperature coefficient (Q10) show?
how much the rate of reaction changes when the temp is raised by 10 ‘C
explain how pH affects enzymes
the H+ and OH- ions interact and break the ionic bonds and H-bonds, changing the shape of the active site
give two experiments used to measure rate of reaction
- breakdown of hydrogen peroxide (using catalase)
- breakdown of starch (using amylase)
name the factors that may affect an enzyme reaction
temp / pH / enzyme conc / substrate conc
what is a buffer ?
a solution able to resist changes in pH when small amounts of acid / alkali are added
what is a cofactor?
a Substance that is Required by some Enzymes for them to work
what is the cofactor of amylase ?
chloride ions
how do inorganic cofactors help the enzyme ?
help enzyme and substrate bind together (not used up/changed)
what are co enzymes ?
organic cofactors
how do co enzymes help enzymes ?
act as carriers, by moving chemicals between enzymes (changed by reaction) - they are continually recycled
what is a cofactor tightly bound to an enzyme known as ..?
prosthetic group
what is the prosthetic group for carbonic anhydrase ?
zinc ions
what are enzyme inhibitors ?
molecules that bind to enzymes and prevent them from performing their function (may be competitive/non-competitive)
how do competitive inhibitors inhibit ?
- similar shape so fit active site
- compete with substrate to bind with enzyme
- block substrate molecule from binding
Describe rate of reaction with competitive inhibitors
rate of reaction will increase as substrate concentration increases
how do non-competitive inhibitors inhibit ?
- bind to allosteric site
- causes change in active site shape
- substrate no longer able to bind
Describe rate of reaction with non-competitive inhibitors
increasing substrate concentration will have little effect on rate of reaction
when are inhibitors reversible ?
weak hydrogen / ionic bonds between enzyme and inhibitor
when are inhibitors irreversible ?
strong covalent bonds between enzyme and inhibitor
Describe the role of reverse transcriptase inhibitors
inhibit the enzyme reverse transcriptase, which catalyses the replication of viral DNA
how does penicillin work ?
- inhibits the enzyme transpeptidase, which catalyses formation of proteins in bacterial walls
- weakens cell wall and prevents regulation of osmotic pressure
- cell bursts (bacterium killed)
how is cyanide dangerous ?
irreversible inhibitor of the enzyme cytochrome c oxidase, which catalyses respiration reactions
how is malonate dangerous ?
inhibits enzyme succinate dehydrogenase (catalyses respiration reactions)
how is arsenic dangerous ?
inhibits enzyme pyruvate dehydrogenase (catalyses respiration reactions)
what is a metabolic pathway ?
series of connected metabolic reactions
what is product inhibition ?
when the product inhibits the enzyme that catalyses the reaction (reversible)
what is end-product inhibition ?
when the end product of the metabolic pathway inhibits enzyme at start (reversible)
why are some enzymes synthesized as inactive precursors ?
prevent them from causing damage to cells
define biological catalyst
a protein that speeds a metabolic reaction without getting used up / changed
what to remember when describing graphs
describe steepness as well
what is V max ?
max rate at which the enzyme catalyses a reaction
what terms to remember to use with enzymes …
enzyme - substrate complex
complementary binding
specific
what word is used to describe flat graph
plateau
what is vitamin B12 required for ?
successful transfer of methyl groups
what is vitamin B3 required for ?
acts a an antioxidant
