Unit 1: Enzymes Flashcards
What is the equilibrium constant equation ?
K = Kf/ Kr
What is the transition state ?
A part of any chemical reaction where old bonds are incompletely broken and new bonds are incompletely formed
What are 3 ways enzymes lower the transition state of a reaction ?
- Proximity
- Orientation
- Microenvironment
What is proximity in relation to enzymes and the transition state ?
When enzymes bring substrates together and this increases rate by 10^5-10^8
What is orientation in relation to enzymes and transition state ?
When an enzyme orients substrates so that they can best attain the most favourable position to achieve transition state
What is microenvironment in relation to enzymes and transition state ?
The idea that an active site can provide protection to a non aqueous environment
What is the optimal conformation of a binding site ?
One that precisely contours the transition state of the reactants
How is catalysis achieved ?
When amino acid residues are brought close together in their tertiary structure to form an active site
What is the induced fit model of enzyme action ?
The idea that the active site moulds itself around the substrate. This leads to the enzyme changing conformation upon substrate binding
What is the Michaelis-Menten theory of kinetics ?
That enzymes act by increasing the rates of both the forward and reverse reactions equally. This does not change the equilibrium constant
What is the Michaelis-Menten kinetics equation ?
S + E <——> ES —–> P + E
What does E stand for in the Michaelis-Menten kinetics equation ?
E = Enzyme
What does S stand for in the Michaelis-Menten kinetics equation ?
S = Substrate
What does ES stand for in the Michaelis-Menten kinetics equation ?
ES = Enzyme substrate complex
What does P stand for in the Michaelis-Menten kinetics equation ?
P = Product
What is a hyperbolic curve ?
The relationship between the rate of reaction and concentration of the substrate
What is the term used for the effect of temperature on reaction rate ?
Fundamental
What is the term used for the effect of temperature on denaturation rate ?
Consequential
What does the PH optimum often reflect ?
PH sensitive events at the active site
What is the idea of an enzyme pathway ?
That enzymes rarely operate alone, they are part of a chain of reactions known as a pathway.
What is an allosteric enzyme ?
Type of enzyme that can change its activity or shape in response to the binding of a molecule at a site other than its active site
What shape do allosteric enzymes display on a graph ?
A sigmoidal S-shaped curve
What is the function of an allosteric inhibitor ?
- Stabilising the inactive state
- This decreases affinity of enzyme for the substrate
What is the function of an allosteric activator ?
- Stabilising the active state
- This increases the affinity of the enzyme for the substrate
How can enzyme activity be controlled/ regulated (4) ?
- Control by covalent modification, especially phosphorylation
- Control by regulatory proteins and/ or nucleotides
- Control through ion binding
- Control through proteolysis
What are enzymes that bring about phosphorylation called ?
Kinases- they induce phosphorylation
What are enzymes that cause dephosphorylation called ?
Phosphatases- they cause dephosphorylation
What are the 2 forms of kinase ?
- Serine/threonine kinases
- Tyrosine kinases
What is the EF hand motif ?
The hand motion that says the calcium binding site is located in a tight loop connecting two alpha helixes (E and F)
