Chapter 7 - Metabolic Components Flashcards
What is a catalyst?
any substance which can provide an alternative route or an alternative transition state (they lower the transition state’s activation energy)
How can a competitive inhibitor be overcome?
It can be overcome at high concentrations of substrate.
Lineweaver-Burk plot of mixed inhibition
What is a mixed inhibitor?
a molecule that can bind the free enzyme or the enzyme-substrate complex, but has a greater affinity for one state over another (this specifically is how it differs from a non-competitive inhibitor)
Michaelis-Menten kinetics graph
Beginning of graph: rate depends on [S] (first order)
End of graph: rate depends on [E] (zero order)
Coenzyme A structure
Lineweaver-Burk plot of competitive inhibition
In the reaction A –> B, if k1 > k2, then at equilibrium how do their concentrations differ?
[B] > [A]
Where is the phosphomonoester linkage in ATP?
between the C5’ of the ribose ring and the first phosphate group
What is the active site of an enzyme?
the specific site to which a specific substrate molecule will bind
What is a competitive inhibitor?
a molecule that resembles the normal substrate and can readily bind the active site of the enzyme to form an enzyme-inhibitor complex (EI)
In competitive inhibition, what is the effect on Vmax?
It is unchanged - initially, there is a lower Vmax for a given substrate concentration, but as substrate concentration increases, [I] becomes negligible and the same Vmax can be reached.
Lineweaver-Burk plot of non-competitive inhibition
What are the 3 main active residues in chymotrypsin’s active site (catalytic triad)?
serine, histidine, aspartic acid
Lineweaver-Burk kinetics plot
Michaelis-Menten graph of competitive inhibition
NAD structure
Where is the phosphoric anhydride linkage in ATP?
between each phosphate group
Michaelis-Menten graph of non-competitive inhibition
What is the active site of coenzyme A?
a sulfhydryl group (-SH)
What is the shape of the Michaelis-Menten graph?
hyperbolic
What is convergent evolution?
Molecules/organisms that are similar evolved independently of each other, but are similar due to the environment.
General reaction for an enzyme + substrate
E + S <—> ES —> E + P
k1: E + S –> ES
k2: E + S <– ES
k3: ES –> E + P
Describe the general mechanism of chymotrypsin
- At physiologic pH, aspartic acid is deprotonated. It makes its neighbor Histidine more basic. As a result, Histidine can deprotonate its neighbor Serine to form an alkoxide ion.
- In the presence of an ester/peptide, Serine’s alkoxide ion can attack the carbonyl carbon, forming an unstable tetrahedral intermediate. The electrons reform the carbonyl, kicking off the amino group.
- Water enters, and is deprotonated by Histidine. The OH attacks the carbonyl, again forming an unstable tetrahedral intermediate. The electrons reform the carbonyl, kicking off the bond to Serine, and allowing the new acid to leave the enzyme.