Enzymes Flashcards
What symbol represents transition states in enzymatic reactions?
Double dagger symbol (‡)
This notation is used to indicate the state during the transition of a reaction.
Are all enzymes proteins?
No, some are catalytic RNA molecules
This was discovered in the 1980s.
What is the typical reaction rate increase of enzymes compared to uncatalyzed reactions?
106 to 1012 times greater
This highlights the efficiency of enzymatic reactions.
Under what conditions do enzymes typically function?
Temperature <100, 1 Atm pressure, neutral pH
These conditions are generally mild compared to many chemical reactions.
What is an example of reaction specificity in enzymes?
Glucose oxidase with glucose as its natural substrate
The reaction rates significantly differ with changes in stereoisomerism.
What are the complementary features of a substrate to an enzyme?
- Shape
- Hydrophobicity
- Charge
- Hydrogen bonding
These features facilitate the binding of the substrate to the enzyme.
What illustrates the concept of enzyme-substrate interaction?
Lock and key model
The enzyme is the lock, and the substrate is the key.
What is the more recently accepted model of enzyme-substrate interaction?
Induced fit model
This model suggests that the enzyme changes shape to fit the substrate.
What are the points of control in metabolic pathways?
- Activated by small molecules (activators or inhibitors)
- Modulated by covalent modification
These controls are essential for regulating enzyme activity.
What suffix is commonly used in enzyme nomenclature?
-ase
Enzymes are often named after their substrates or the type of reaction they catalyze.
What is a prosthetic group in the context of enzymes?
Always covalently bound to the enzyme
These groups are essential for enzyme activity.
What is the transition state in a reaction profile?
A high-energy state between reactants and products
This state is not stable enough to exist officially.
How do enzymes affect activation energy?
They lower the activation energy barrier
Enzymes do not change the position of equilibrium.
What are the four general catalytic mechanisms of enzymes?
- Acid-base catalysis
- Covalent catalysis
- Metal ions in catalysis
- Proximity and orientation
These mechanisms describe how enzymes facilitate reactions.
What is preferential substrate binding?
When an enzyme stabilizes substrate binding, slowing the reaction rate
This can lead to a higher activation energy.
What is preferential transition state binding?
Stabilizing the transition state to lower activation energy
This is crucial for increasing reaction rates.
What happens if an enzyme preferentially binds to its product?
The reaction rate slows down due to product being trapped
This scenario prevents the enzyme from effectively catalyzing the reaction.
What are transition state analogues?
Stable molecules resembling the transition state that inhibit enzymes
These analogues are often used in drug design.
What is the main function of HIV protease inhibitors like Saquinavir and Ritonavir?
They block and inhibit the HIV protease by mimicking the transition state
This is essential for halting the viral life cycle.
What is the significance of the Michaelis-Menten Equation in enzyme kinetics?
It relates the rate of enzymatic reactions to substrate concentration
This equation is fundamental for understanding enzyme kinetics.
What is Km in the context of enzyme kinetics?
The substrate concentration that gives a rate equal to half of Vmax
Km is a key parameter in enzyme kinetics.
lml
What is the Michaelis constant, Km?
Km is defined as Km = Ks + (K2/K1), where Ks is the equilibrium dissociation constant for ES and K2 is another name for Kcat.
Km provides a measure of the affinity of the enzyme for its substrate.
How does Km relate to enzyme affinity?
Low Km = high affinity, High Km = low affinity.
A high Km value indicates a greater concentration of substrate is needed to achieve Vmax.
