7. The Active Site Flashcards
what did Linus Pauling hypothesise
enzymes active site is not complimentary to the substrate but to the transition state of the substrate
what is Km
a measure of the affinity of the active site for the substrate
describe the induced fit model (Koshland)
- the active site is only partially complimentary to the substrate
- binding of substrate induces conformational change in enzyme structure
- distortion of the active site bends the substrate into the transition state
what is the function of the catalytic site
performs catalysis
how many dimensions is a normal active site
3 dimensional pocket or groove
what is the orbital steering effect
substrates orientate relative to catalytic groups in the active site
what are apoenzymes
enzymes which are inactive and cannot function
what are holoenzymes
enzymes which are active due to presence of cofactors/ coenzymes
give an example of a permanent coenzyme
haem in haemoglobin
what is the major role of coenzymes
transfer chemical groups between substrates
what are most cofactors
mostly metals
what is the main purpose of cofactors
extend the range of chemical reactions that enzymes can catalyse
where do cofactors bind
not in the catalytic site
bind near or in active site
name 2 other functions of cofactors
- assist in substrate binding and stabilisation
2. stabilise the catalytic state (holding it in the right conformation)
what are the three main reaction mechanisms
acid-base catalysis
covalent catalysis
electrostatic catalysis
