Enzymes Flashcards
(14 cards)
What is a substrate in enzymatic reactions?
A substrate is the specific reactant that an enzyme acts upon during a biochemical reaction. It binds to the enzyme’s active site to form an enzyme-substrate complex.
What is the Lock and Key model of enzyme-substrate interaction?
The Lock and Key model suggests that the enzyme’s active site has a specific shape that exactly matches the shape of its substrate—like a key fitting into a specific lock.
What is the Induced Fit model of enzyme-substrate interaction?
The Induced Fit model proposes that the enzyme’s active site is flexible and molds itself around the substrate when it binds, enhancing the fit and promoting the reaction.
How do the Lock and Key and Induced Fit models differ
The Lock and Key model implies a rigid active site, while the Induced Fit model involves a flexible active site that adapts to the substrate’s shape upon binding.
Enzyme cofactors
-Non-protein components of enzymes for catalytic activity
expand the limited chemical repertoire of amino acid side chains
-Enzymes require more than one cofactor for activity
What is a metal-activated enzyme?
A metal-activated enzyme requires a metal ion (like K⁺, Mg²⁺, or Ca²⁺) for activity, but the metal is not tightly bound and can be added or removed easily
What is a metalloenzyme?
A metalloenzyme contains a tightly bound metal ion (like Fe²⁺, Zn²⁺, or Cu²⁺) that is essential for the enzyme’s structure or function.
What is a co-substrate?
A co-substrate is a type of coenzyme that temporarily binds to the enzyme and is changed during the reaction. It must be regenerated before it can be reused.
What is V₀ in terms of reaction velocity?
V₀ (initial velocity) is the rate of an enzyme-catalyzed reaction measured right after the reaction begins—when the substrate concentration is high and product formation is still minimal. It reflects the enzyme’s activity before significant substrate depletion or product inhibition occurs.
What is Vmax in enzyme kinetics?
Vmax is the maximum reaction velocity achieved by an enzyme when all active sites are fully saturated with substrate. It represents the fastest rate at which the enzyme can convert substrate to product. It os proportional to [E]
What are the main features of the Michaelis-Menten model?
Enzymes bind reversibly to substrates to form an ES complex.
The ES complex either dissociates back to E + S or proceeds to form product.
Product formation is assumed to be the rate-limiting step.
The model assumes steady-state, meaning [ES] remains constant during the initial phase of the reaction.
What is Kₛ in enzyme kinetics?
Kₛ is the dissociation constant for the enzyme-substrate complex (ES). It describes the equilibrium between the free enzyme and substrate and the ES complex
What is Kₘ (Michaelis constant) in enzyme kinetics?
Kₘ is the substrate concentration at which the initial velocity (V₀) is half of the maximum velocity (Vmax)
Explain the shape of a typical Michaelis-Menten plot using the Michaelis-Menten equation.
The curve is hyperbolic.
At low substrate concentrations, 𝑉0 increases rapidly with [S].
As [S] increases, the curve levels off toward Vmax.
When [S] = Km,
𝑉0 =𝑉𝑚𝑎𝑥/2
This reflects saturation kinetics: enzyme active sites become fully occupied as [S] increases.
