1.4 Flashcards
enzymes
define catalyst
a substance that speeds up a reaction without changing the substances produced or being changed its self
define enzyme
proteins that have specific shapes which act as biological catalyst controlling rate of the reactions taking place in an organism
what type of a protein in an enzyme
globular
what factors effect enzymes and why
pH and temperature as they affect the intramolecular bonds within the protein
what is an anabolic reaction
a reaction that synthesises new molecules in a cell
what is a catabolic reaction
a reaction which breaks down substances within a cell
what is metabolism
the sum of anabolic and catabolic processes in a cell
what is a metaboilc chain/pathway
a series of linked reactions in the metabolism of a cell
what are intracellular enzymes
enzymes that catalyse reactions within the cell
what are extracellular enzymes
enzymes that catalyse reactions outside of the cell in which they were made
what is activation energy
the minimum amount of energy required to initiate a reaction
how does an enzyme work
specific shape complementary to one substrate
substrate binds to active site which affects the bonds in the substrate making them easier to break
reacting substances are brought closer together making it easier for bonds to form between them
when the products are made they no longer fit in the enzyme so they are released
what is the induced fit hypothesis
the active site is considered to have a more flexible shape and once the substrate enters the active site the shape if modified to form an active complex then relaxes when the products are released
what are the control variables when looking at the effect of an enzyme on rate of reaction
conc of substrate & enzyme
temperature
pH
what is molecular activity/turnover number
the number of substrate molecules transformed per minute by a single enzyme molecule
what are enzyme inhibitors
substances that slow down enzymes or stop them from working
what are the 2 main reversible inhibitors
competitive inhibitor
non-competitive inhibitor
what is a competitive inhibitor
the inhibitor molecule is a similar shape to the substrate and they compete for the active site of the enzyme so level of inhibition is effected by conc of substrate and inhibitor
what is a non-competitive inhibitor
inhibitor which forms a complex with enzyme or enzyme substrate complex by binding elsewhere on the enzyme (not to the active site) so only the concentration of inhibitors effects level of inhibition
how does a irreversible inhibitor work and give examples
combines with the enzyme by permanent covalent bonds to groups vital for catalysis to occur causing the enzyme to become inactivated permanently
examples; poisons such as arsenic, cyanide and mercury
what are regulatory enzymes
enzymes which have a site separate to the active site where another molecule can bind to have either a binding or inhibitory effect
they are found in complex metabolic pathways such as photosynthesis and respiration
what is end-product inhibition and give an example
regulatory enzyme which is found near the beginning of pathways which is inhibited by on of the end products
example: PKF controls rate of respiration which is involved in the production of ATP
