1.8. Enzymes Flashcards
Enzymes have a ___ structure.
quaternary
enzymes’ function
speed up chemical reactions by converting substrates into products without being changed themselves
- catalysts in living organisms (proteins) - no polymerization or cell respiration without enzymes
Why do living organisms produce thousands of different enzymes?
Because (most) enzymes catalyze only one biochem reaction (enzyme-substrate specificity)
the basis for enzyme-substrate specificity
the shape and chemical properties of its active site (region on enzyme’s surface to which S bonds) - they have to be complimentary with the shape and chem. properties of the S
why does the product/do the products detach from the enzyme after their creation
S is converted into P while inside of the enzyme - P is not the substrate specific to the enzyme so has to leave
two models of the enzyme activity
1) lock and key model (very specific)
2) induced fit model - more than one S (similar like glucose, fructose, galactose)
- S induces a conformational change of the enzyme (closes on the S)
activation energy
E needed for the destabilization of bonds in an aqueous substrate (increase in temp = Ek increased, movement breaks bonds, not an option with living organisms (they would die of the high temp.)
How do enzymes speed up reactions?
Enyzmes minimize the activation E by destabilizing and breaking the chemical bonds of a S - this is what Ea usually does so E replace heat to some extent (not completely - decrease the Ea).
Attraction forces between the S and active site are weak but there are many of them so together they overpower the bonds
- enzyme activity at 37°C - body temp
enzyme-catalyzed reactions require ___ activation energy than normal, because…
smaller, less E has to be invested to break bonds (enzymes break many)
transition state
the moment when active site bonds overpower the bonds within the S (neither-nor)
Some enzymes convert two S into one P by…
…weakening some bonds within S and strengthening some others (sucrose <-> glucose + fructose)
enzyme-catalyzed reaction is faster
100-1000x
factors affecting enzymatic activity
1) substrate concentration
2) pH
3) temperature
4) inhibitors (opposite is activators)
r/C(S) graph
exponential growth phase (the more S the more collisions between S and E, more E-S complexes formed), transition state (growth slows), plateau phase (constant r) - run out of active sites (limited no. of enzymes)
r/pH
rate of reaction is at its peak at the optimal pH for that specific E (E conformation changed with small difference in pH (small drop in r) - big difference = denaturation - irreversible - less E to react with S and therefore lower r)
