Biochemistry Chapter 3: Enzymes Flashcards
definition of Km
Concentration of substrate needed to reach reaction rate of 1/2 of Vmax
analog
compound with a structure similar to another molecule, allowing it to mimic, activate, inhibit, or interfere with the function of the original molecule in a biological system, depending on its specific properties and the context of its interaction.
Suicide Inhibition
occurs when an enzyme binds the inhibitor (structurally a substrate analogue) and forms an irreversible complex with it, usually through a covalent bond.
Difference between phosphorlyase and phosphatase
Phosphorlyase adds phosphate (It adds a phosphate group without ATP by breaking a bond using inorganic phosphate)
Phosphtase removes phosphate It removes a phosphate group using water (hydrolysis).
kcat
turnover number. is the maximum number of substrate molecules an enzyme can convert to product per active site per unit time when the enzyme is fully saturated with substrate. It is expressed as:
Hill coefficient greater than 1
cooperativity
Hill coefficient = 1
Non-cooperative (independent binding) Each ligand binds independently, with no effect on affinity.
hill coefficient < 1
Negative cooperativity. Binding of one ligand decreases the affinity for subsequent ligands.
Difference between specificity and affinity
Specificity refers to an enzyme’s ability to distinguish and act on a particular substrate among many options, while affinity describes how tightly an enzyme binds to its substrate, often measured by the Kₘ value.
Km vs Kd
Kₘ (Michaelis constant) measures the substrate concentration at which an enzyme operates at half of its maximum velocity (Vmax). A lower Kₘ means higher affinity because the enzyme reaches half-max activity at a lower substrate concentration.
K_d (Dissociation constant) measures the binding affinity between two molecules, such as a ligand and a receptor (or an antibody and an antigen). It represents the equilibrium between bound and unbound states. A lower K_d means higher affinity, as it indicates that the two molecules stay bound more tightly and dissociate less.
Which type of inhibitor does NOT alter the KM/Vmax ratio of an enzyme?
Uncompetitive (slope doesn’t change between inhibited and not inhibited)
catalytic efficiency
kcat/km
When experiments are performed on enzymes that display traditional Michaelis–Menten kinetics, what shape does the graph of V0 versus substrate concentration [S] have?
Hyperbolic
What is the order with respect to each reactant and the overall reaction order? And the rate law?
What are the units for k (rate constant)
What is the Arrhenius Equation?
How to use the Arrhenius Equation
protein unfolding is typically what rate order
A general unimolecular reaction follows:
Folded protein -> Unfolded protein
Rate=k[FoldedProtein]
Therefore, it’s first order
