Chapter 5: 5.1 Kinetics Flashcards
Define:
Kinetics
The study of enzymatic reactions
What does kinetics investigate?
Investigates the maximum rate of reaction as well as substrate and/or inhibitor specificity
What do enzymes do?
Lowers the energy barrier a reaction must overcome
True or False:
The enzyme contributes to the reaction
False, the enzyme does not contribute to the reaction (is in native state at the end of reaction)
True or False:
Enzymes can alter the equilibrium of the reaction
False, enzymes do not alter the equilibrium of the reaction
Define:
Rate of reaction (V)
The quantity of substrate that disappears in a unit of time
Define:
Initial rate of reaction (V0)
Rate when substrate concentration is constant
Define:
Maximum rate of reaction (Vmax)
Maximum rate of reaction when the enzyme is saturated by substrate
State:
Formula for V0
V0 = Δ[S] / Δt
Define:
Michaelis-Menten Equation
A way of expressing the relationship between initial velocity, maximum velocity, and initial substrate concentration
State:
Michaelis-Menten Equation
V0 = Vmax * ([S] / (Km + [S]) ) = kcat * ( ([E] * [S]) / (Km + [S]) )
Define:
Michaelis-Menten constant (Km)
The [S] at which V0 = 1/2 Vmax
* Indicates how [S] affects enzyme function
State:
Michaelis-Menten constant (Km)
Km = (k2 + k-1) / k1
State:
The relationship between efficiency of an enzyme and the Km value
The lower the Km value, the more efficient the enzyme is
Define:
Turnover Number (kcat)
The maximum theoretical reaction rate for a single saturated enzyme
If kcat = 9 s^-1, what does this mean?
Every 1 second, 1 enzyme can process 9 substrate molecules
State:
Turnover Number (kcat)
kcat = Vmax / [E]
State:
The relationship between power of the enzyme and the kcat value
The higher the kcat value, the more powerful the enzyme is
Define:
Specificity Constant (kcat/Km)
The ratio of the turnover number and the Michaelis-Menten constant
What is the Specificity Constant (kcat/Km) used for?
Used to compare enzymes
* The higher the ratio the more efficient and more powerful (overall better) the enzyme
Define:
Lineweaver-Burke Plot
The double reciprocal of the Michaelis-Menten equation
What does the Lineweaver-Burke Plot allow for?
Allows for a more precise identification of Vmax and Km
State:
Lineweaver-Burke Plot equation
1/V0 = Km/Vmax * 1/[S] + 1/Vmax
Define:
Inhibitors
Any molecule that binds to an enzyme and inhibits its function (slows the rate of reaction)
True or False:
The stronger the inhibitor, the higher concentration needed to impact rate
False, the stronger the inhibitor the lower concentration needed to impact rate
What are the types of inhibitors?
- Reversible inhibition
- Irreversible inhibition
Describe:
Reversible inhibition
Reversibly inactivates enzymes
* Inhibitor binds non-covalently to the enzyme
What are the two methods of reversible inhibition?
- Competitive inhibition
- Non-competitive inhibition
Describe:
How revesion occurs in competitive inhibition
Reversion occurs through increasing amount of substrate (out-competes for active site)
Describe:
How reversion occurs in non-competitive inhibition
Effects are reversed by lowering inhibitor concentration
Describe:
Irreversible inhibition
Inhibitor covalently binds to the active site of the enzyme
True or False:
In irreversible inhibition, inhibitor closely resembles the substrate or a transition state
True
Describe:
Competitive inhibition
Inhibitors which compete with the substrate for binding to the active site
Competitive inhibition ——- the rate at which the enzyme binds the substrate
Reduces
In Competitive Inhibition of Enzymes:
State what happens to:
1. Vmax
2. Km
If reversible,
1. Does not change Vmax
2. Increases Km
Describe:
Non-competitive inhibition
Inhibitors binds to a site on the enzyme somewhere other than the active site
In Non-Competitive Inhibition of Enzymes:
State what happens to:
1. Vmax
2. Km
- Lower Vmax
- Km is unchanged
For a competitive inhibitor:
- Effect on Vmax
- Effect on Km
- How it is reversed
- Vmax is unchanged
- Km is increased
- Reversed through increasing [Substrate]
For non-competitive inhibitor:
- Effect on Vmax
- Effect on Km
- How it is reversed
- Vmax is decreased
- Km is unchanged
- Reversed through decreasing [Inhibitor]
How do the effects of irreversible inhibitors compare to reversible inhibitors?
Same as what is seen for Non-Competitive Reversible inhibitors
How are effects for irreversible inhibitors diminished?
Diminished through decreasing the concentration of inhibitor
