Enzymes Flashcards
how does an enzyme work ?
- enzymes decrease activation energy = increasing rate of reaction
what is the lock and key hypothesis ?
- active site has rigid shape
- substrate shape is complementary to active site
- ESC is formed then EPC
what is the induced fit hypothesis ?
- active site is flexible
- active site changes shape to fit substrate
- ESC then EPC formed
how does pH affect enzyme activity ?
- enzymes active at optimum pH
- high or low pH can denature enzymes as tertiary structure is disrupted
how does temperature affect enzyme activity ?
- high temperature = denaturation
- inc temp - inc ke more frequent collisions
what is an apoenzyme ?
- inactive protein part of an enzyme
- needs a cofactor to be active
what is a holoenzyme ?
- enzyme along with cofactor
what is a cofactor ?
- either organic or inorganic
- help enzyme function
what is an inorganic cofactor ?
- metal ions
- eg. Zn2+ for carbonic anhydrase
what is an organic cofactor ?
- prosthetic groups (heam)
- coenzyme (NAD)
what is the difference between prosthetic groups and co-enzymes ?
- co-enzymes are temporarily bound whereas prosthetic groups are tightly bound
what are the 6 classifications of enzymes ?
- Ligase
- Isomerases
- Lyase
- Hydrolases
- Oxidoreductases
- Transferases
what are transferase enzymes ?
- transfer a functional group between molecules
- eg. kinases transfer phosphate groups
what are ligase enzymes ?
- catalyse synthesis of new covalent bonds using ATP
- eg. DNA Ligase
what are oxidoreductase enzymes ?
- catalyse transfer of electrons
- eg. lactate dehydrogenase
what are isomerase enzymes ?
- catalyse conversion of isomers, transferring groups within the same molecule
- eg. cis trans isomers
what are hydrolase enzymes ?
- addition of water to break bonds
what are 3 types of hydrolase enzymes ?
- phosphatases (ester bonds)
- lipases (ester bonds - lipids)
- peptidases (peptide bonds - forms 2 products )
what are lyase enzymes ?
-catalyse addition or removal of H20 , CO2 , NH3 to create double bonds
- eg. dehydrase, decarboxylase. deaminase
what are Isoenzymes ?
- different amino acid sequence but catalyse the same reaction
what is allosteric regulation ?
- effector can bind to allosteric site and either speed up or slow down action
what is feedback inhibition ?
- the end product binds to an enzymes at the start of the pathway to stop further synthesis
What do kinase enzymes do?
- Add phosphate groups
