MODULE 6: Chapter 7.2 Flashcards
What is the formal definition of a catalyst?
A catalyst increases the rate of a chemical reaction without changing the chemical equilibrium and is not consumed by the reaction.
How do enzymes increase the rate of a reaction inside cells?
- Stabilizing the transition state to lower the activation barrier.
- Providing an alternative path for product formation.
- Orienting substrates appropriately for the reaction.
What can lead to increased reaction rates besides enzymes?
Raising effective substrate concentrations or elevating the reaction temperature or pressure.
How do enzymes optimize molecular structure and function?
Through natural selection to achieve increased rates of reactions under physiologic conditions.
What is the role of enzyme active sites?
They provide a physical and chemical environment that promotes product formation.
What are the three specific physical and chemical properties of enzyme active sites?
- Sequestered microenvironment.
- Binding interactions that facilitate formation of the transition state.
- Presence of catalytic functional groups.
What does the enzyme active site do to the substrate?
It provides an optimal orientation relative to reactive chemical groups and increases the reactivity of some functional groups.
How do enzyme active sites exclude excess solvent?
By either an induced-fit mechanism or by sequestering the active site away from the surface.
What is the induced-fit mechanism in enzyme activity?
Conformational changes in the protein create significant shape and chemical complementarity between the substrate and enzyme, ejecting excess water.
What happens when glucose binds to hexokinase?
Numerous water molecules are displaced from the substrate binding site.
What is the significance of the aldolase reaction?
It converts two phosphorylated three-carbon compounds into one bisphosphorylated six-carbon compound.
What is the reaction coordinate diagram used for in enzyme-catalyzed reactions?
To compare the activation energy of enzyme-catalyzed reactions to uncatalyzed reactions.
What is the transition state stabilization model?
It proposes that the active site shares more complementarity with the transition state than with the substrate or product.
Fill in the blank: Enzymes stabilize the _______ within the active site.
[transition state]
True or False: The free energy change (ΔG) for a reaction changes in the presence of an enzyme.
False.
What types of interactions contribute to substrate binding in enzyme-catalyzed reactions?
Hydrogen bonds, ionic interactions, and van der Waals interactions.
What is the significance of the hydrophobic effect in enzyme activity?
It increases the entropy of water molecules released upon substrate binding.
What happens after the enzyme-bound substrate is converted to the enzyme-bound product?
The product is released from the enzyme.
What is the relationship between enzyme active sites and excess water?
Active sites are designed to exclude excess water that can interfere with reactions.
How do hydrophobic substrate channels function in enzymes?
They prevent water molecules from entering the active site while allowing access to hydrophobic substrates.
What is an example of a metabolic enzyme discussed in the content?
Aldolase.
What is the role of the amino acid functional groups within the aldolase active site?
They position the substrates to favor aldol condensation.
How does the enzyme ensure that product release does not interfere with reaction rates?
Binding should not be too tight to allow product release and new substrate binding.
What is the role of the ES complex in lowering activation energy?
Formation of the ES complex initiates bond formations that lower activation energy required to reach the transition state
