Lecture 14: Chemical reactions and enzymes Flashcards
1
Q
Define Gibbs Free Energy and describe its relationship to endergonic and
exergonic reactions
A
- The amount of energy in a system that is available to do work.
- Endergonic (anabolic) reactions have a positive delta G (products have more free energy than reactants). Endergonic are spontaneous.
- Exergonic (catabolic) reactions have a negative delta G (reactants have more free energy than products). Exergonic are non-spontaneous.
2
Q
Equation for calculating
ΔG
A
ΔG = ΔH − TΔS
3
Q
Know the process of ATP hydrolysis
A
−ΔG = −ΔH – TΔS
ATP + Water = ADP + P
4
Q
Describe the coupling of endergonic and exergonic reactions
A
Process in which a spontaneous reaction (ΔG<0) drives a non-spontaneous reaction (ΔG>0).
5
Q
Define the activation energy of a reaction and describe the role of
enzymes
A
- Enzymes reduce the activation energy by stabilizing the
transition state
6
Q
Describe the active site of an enzyme (including its formation and
interaction with substrate molecules)
A
- Active site: region of an enzyme that binds the substrate and converts
it to the product. - Active site is formed by protein folding that brings amino acids close to each other.
- Interactions between substrate and active site are typically
non-covalent and help stabilize the transition state; results in a
decrease of the activation energy
7
Q
Describe and compare competitive inhibition, non-competitive inhibition,
and allosteric activation
A
Inhibitors:
- Irreversible, form covalent bonds.
- reversible, form weak bonds. Competitive, bind to the active site. Non-competitive bind elsewhere (AKA allosteric inhibition).
8
Q
Describe positive and negative feedback
A
Threonine Dehydratase is an allosteric enzyme: activated or inhibited when bound to another molecule that changes its shape • Allosterically activated by threonine (activators are agents of positive feeback). • Allosterically inhibited by isoleucine (inhibitors are agents of negative feedback).
