Untitled Deck Flashcards
(26 cards)
What are enzymes?
Biological catalysts that speed up reactions without being consumed.
What type of macromolecule are most enzymes?
Proteins (specifically globular proteins).
What is the function of the active site of an enzyme?
It binds the substrate and catalyzes the reaction.
What is the enzyme-substrate complex?
A temporary molecule formed when an enzyme binds its substrate.
Do enzymes change the equilibrium of a reaction?
No, they only affect the rate at which equilibrium is reached.
How do enzymes lower the activation energy?
By stabilizing the transition state and bringing reactants together efficiently.
What is the induced fit model?
The enzyme changes shape to better accommodate the substrate during binding.
What type of interactions occur in the active site?
Weak interactions like hydrogen bonds, ionic interactions, hydrophobic forces.
Name two amino acids commonly found in enzyme active sites.
- Histidine
- Serine
What does Vmax represent?
The maximum velocity of an enzyme-catalyzed reaction when fully saturated with substrate.
What does Km (Michaelis constant) represent?
The substrate concentration at which the reaction rate is half of Vmax.
What kind of graph is used to show enzyme kinetics?
Michaelis-Menten plot: substrate concentration vs. initial velocity (V₀).
What does a Lineweaver-Burk plot show?
A straight-line version of enzyme kinetics using 1/[S] and 1/V₀ to calculate Vmax and Km.
What is competitive inhibition?
Inhibitor binds the active site; can be overcome by more substrate; increases Km, Vmax unchanged.
What is uncompetitive inhibition?
Inhibitor binds only to the enzyme-substrate complex; decreases both Km and Vmax.
What is mixed inhibition?
Inhibitor binds to enzyme or ES complex; affects both Km and Vmax differently.
What is irreversible inhibition?
Inhibitor binds permanently (often covalently); enzyme function is permanently lost.
What is a cofactor?
An inorganic ion (e.g., Fe²⁺, Mg²⁺) required for enzyme activity.
What is a coenzyme?
An organic molecule (e.g., FAD) that assists in enzyme catalysis; often derived from vitamins.
What is a prosthetic group?
A tightly or covalently bound coenzyme or metal ion essential for enzyme function.
What is an allosteric enzyme?
An enzyme regulated by binding of molecules at sites other than the active site.
What is an allosteric modulator?
A molecule that increases or decreases enzyme activity via conformational change.
What shape do allosteric enzyme kinetics curves have?
Sigmoidal (S-shaped), showing cooperativity.
What are T and R states in allosteric enzymes?
- T (tense) = low activity
- R (relaxed) = high activity
