Sesh 6: Enzymes Flashcards
The _________ energy of a reaction defines how likely it is to occur.
Activation.
Define activation energy.
The minimum energy the substrate must have to allow the reaction to occur.
What is the transition state?
The state of the high energy intermediate that lies between the substrate and product.
How can you increase the rate of a reaction?
- Increase temp and conc (but can’t change these too much)- Both increase no of molecules with activation energy and chance of collisions.
- Enzymes- lower the activation energy, favouring formation of transition state.
Define enzymes
Biological catalysts that increase the rate of reaction (forward and backward equally) by lowering the activation energy, thus facilitating the formation of the transition state. They increase the rate at which equilibrium is reached.
What are the group of inheritable enzyme genetic disorders called?
Enzymopathies.
What is the active site of an enzyme?
A cleft or crevice that usually excludes water, formed by amino acids from different parts of the primary sequence.
A small part of the overall protein where the chemical reaction occurs.
Substrate binds weakly, and induces shape change in the active site, so it is complementary (induced fit hypothesis), and forms a complex to hold the substrate in the correct conformation to react.
Substrates bind to enzymes via what type of bonds?
Weak, non-covalent bonds.
What is the normal shape of a plot of reaction velocity as a function of substrate concentration?
A rectangular hyperbola…as [S] increases, velocity increases, but tails off and reaches max velocity.
Predicted by the Michaelis Menten equation.
What does the Michaelis-Menten model propose?
That a specific complex between the enzyme and substrate is a necessary intermediate in catalysis.
Predicts that a plot of reaction rate versus [S] will be a rectangular hyperbola.
* not all enzymes follow these kinetics
Define Vmax.
The maximal rate of reaction, when all enzyme active sites are saturated with substrate.
Define Km.
The substrate concentration that gives half of the maximal velocity. A measure of enzyme affinity for substrate.
A low Km value (units of concentration) indicates the enzyme has _____ affinity for its substrate.
High.
What is 1 international unit of enzyme activity defined as?
The amount of enzyme that produces I micromole of product per min under standard conditions.
The rate of an enzyme catalysed reaction is ______________ to the concentration of enzyme.
Proportional
