Term
|
Definition
| Transfer of electrons (hydride or H atoms) |
|
|
Term
|
Definition
| Hydrolysis reactions (transfer of functional groups to water) |
|
|
Term
|
Definition
| Addition of groups to double bonds or formation of double bonds by removal of group |
|
|
Term
|
Definition
| Transfer of groups within molecules to yield isomeric forms |
|
|
Term
|
Definition
| Formation of C-C, C-O, and C-N bonds by condensation reactions coupled to cleavage of ATP or similar cofactor |
|
|
Term
|
Definition
| sometimes used when generally referring to any additional chemical component that facilitates catalytic activity, but often more specifically to refer to small organic molecules or inorganic ions bound reversibly |
|
|
Term
|
Definition
| more complex organic or metallo-organic molecules bound reversibly |
|
|
Term
|
Definition
- anything bound tightly (permanently); a non-protein part of the enzyme; a coenzyme or metal ion that is very tightly or even covalently bound to the enzyme protein
|
|
|
Term
|
Definition
|
|
Term
|
Definition
| Gibbs free energy; tells how likely it is that the reaction will occur and where the reaction is as far as products, reactants, or equilibrium |
|
|
Term
|
Definition
| a fleeting molecular moment in which events such as bond breakage, bond formation, and charge development have proceeded to the precise point at which decay to either substrate or product is equally likely |
|
|
Term
|
Definition
- made up of just a few amino acids out of the total polypeptide chain; where all the action takes place—i.e. where the binding of substrates and catalysis occurs; chemically and sterically complementary to the transition sate of the reaction
|
|
|
Term
|
Definition
- enzymes change shape to allow the binding of substrate—this is known as the induced fit
|
|
|
Term
|
Definition
- the step in the reaction that has the highest activation energy
- Enzymes do NOT affect the ∆G of the reaction; they just accelerate the reaction
|
|
|
Term
| How does an enzyme achieve specific substrate binding and catalysis of a specific reaction? |
|
Definition
- Enzymes change shape to allow (in sequence) binding of the substrate (induced fit), catalysis, and then the release of substrate
|
|
|
Term
|
Definition
- phase one of the reaction where things aren’t at a constant rate yet
|
|
|
Term
|
Definition
| a nonequilibrium state of a system through which matter is flowing and in which all components remain at a constant concentration; broad maximum of the reaction rate at stage 2 |
|
|
Term
|
Definition
| initial rate of the reaction; the first observable rate; occurs during phase 2 |
|
|
Term
|
Definition
| the substrate concentration at which 1/2Vmax is reached |
|
|
Term
|
Definition
| Vo increases with increasing substrate concentration until this maximal velocity of reached |
|
|
Term
| Which assumptions are made in the derivation of the Michaelis-Menten equation? |
|
Definition
- Assumption #1
- Initially (before the reaction begins to slow down) [P] is low; therefore, K-2 can be neglected
|
|
|
Term
| Which assumptions are made in the derivation of the Michaelis-Menten equation? |
|
Definition
- Assumption #2
- There are many more molecules of substrate S than of enzyme E, and in equation #5 [ES] can be neglected. Furthermore, at least initially, very little substrate has been converted to produce, and [P[ can be neglected as well. Therefore, [S] ≈ [S]t.
- Equation 5: [S] = [S]t – [ES] – [P]
|
|
|
Term
| Michaelis-Menten equation |
|
Definition
|
|
Term
|
Definition
| the number of substrate molecules converted into product per enzyme molecule per time when the enzyme is fully saturated with substrate; known as the turnover number |
|
|
Term
|
Definition
- the speed of an enzymatic reaction is determined by the substrate concentration. The maximal sped is reached when the enzyme is fully saturated with substrate; [ES] ≈ [E]t
|
|
|
Term
|
Definition
- in cells, enzymes are not saturated and the speed very much depends on the substrate concentration.
- In cells [ES] << [E]
- Therefore [S] << Km
- Therefore [E] ≈ [E]t because [E]t = [ES] + [E]
|
|
|
Term
|
Definition
kcat/Km; the rate constant for the conversion of E + S to E + P when [S] << Km
- A large specificity constant is desired
|
|
|
Term
| When is it OK to use the Michaelis-Menten equation to calculate the initial rate, and when do you need to use an alternative equation? What is the alternative equation? |
|
Definition
- When there is a lot of substrate such that the enzymes cn be saturated, the Michaelis-Menten equation can be used
- When there is a lot less substrate than Km [S]<<Km, the other equation for Vo needs to be used because the enzymes most likely won’t be saturated. This is the case when talking about cells because in cells enzymes are not saturated an the speed very much depends on the substrate concentration
|
|
|
