General Properties of Enzymes Flashcards
Enzymes are what types of molecules?
Proteins
What do enzymes do?
They catalyze (increase reaction rate) biochemical reactions.
Is an enzyme consumed and/or altered during a reaction?
No
What do most chemical reactions require to proceed?
Energy
Reactions must absorb enough energy to overcome ____?
The activation barrier
How much energy is required to activate a reaction?
1 mole of energy
What is the energy of activation?
The amount of energy required to activate, or bring to transition state.
What does the ES in ES complex stand for?
Enzyme-substrate complex
Once the substrate is activated, what can happen?
Molecules can go under conversion to product
How do enzymes catalyze a reaction rate?
They provide an alternate pathway with a lower energy of activation requirement.
What does the ES complex break down into?
The free enzyme and the product
Does the ES complex have a higher or lower reactivity?
Higher
What is an ES complex?
It is the physical binding of a substrate to the active site of an enzyme.
What are active sites?
A certain area on an enzyme that shows a specificity for substrates.
Can enzymes be specific for more than one substrate?
Yes
What are the 5 factors affecting enzyme activity?
Temperature, pH, substrate concentration, co-factors, and time
What is the optimum temperature for clinically significant enzymes?
35-39 degrees Celsius
What effect does temperature have on enzymatic activity?
It increases molecular collisions and speeds up the rate of the reaction.
How much does the enzyme reaction rate increase when temperature increases by 10 degrees Celsius?
Reaction rate doubles
The enzymatic reaction rate will double when temperature (in degrees Celsius) is increased by how much?
10 degrees Celsius
In the lab, at what temperatures can enzymes be measured at?
25 degrees, 30 degrees, and 37 degrees
In order to stabilize the enzyme reaction rate, what must be done?
Maintain a constant temperature of +/- 0.1 degree Celsius
How does pH influence enzymatic activity?
Influences extent of dissociation of both substrate and enzyme by changing the shape and charge.
How does pH change the shape of an enzyme?
Denatures the enzyme
How does pH change the ionic state of an enzyme?
Changes the charge on an amino acid residue within the active site
Does each enzyme have a specific pH for optimum activity?
Yes
How does changing the shape and or/charge of an enzyme affect the reaction?
Affects ability of the enzyme and substrate to attract and be bound together. This will change the reaction rate.
What is 1st order kinetics?
As substrate concentration increases, the enzyme activity increases because there is more substrate to react with.
1st order kinetics are proportional to what?
Substrate concentration
What is maximum velocity (Vmax)?
All enzyme is saturated with substrate and any further increase of substrate concentration produces no further increase in maximum velocity.
What is zero order kinetics?
Any further increase in substrate will have no effect on reaction rate.
What is the Michaelis constant?
Km=(k1+k2)/k1
What does the Michaelis constant imply?
It is the substrate that yields 1/2 maximum velocity.
What does velocity depend on?
It depends on the enzyme amount that is bound to the substrate as the ES complex.
When the Km value becomes smaller, what happens?
The attraction between enzyme and substrate becomes stronger.
When the attraction between enzyme and substrate is stronger, will it take more or less substrate to saturate the active site of an enzyme?
Less substrate
A smaller Km value will have what effect on Vmax?
Vmax is reached at a relatively low substrate concentration.
