2.10 introduction to enzymes Flashcards
What is an enzyme catalyst? what is it like at the end of a reaction?
a chemical that speeds up the rate of a chemical reaction. It is chemically unchanged at the end of the reaction because they themselves are not consumed or used up during the course of the reaction.
What effect do catalysts have on activation energy?
Reduces the activation energy
What effect do catalysts have on transition state?
Lowers the energy of the transition state
What is a substrate?
molecule upon which an enzyme acts
How does a substrate interact with an enzyme?
The substrate binds to the enzyme by interacting with amino acids in the binding site
What does the theory of induce fit state?
states that the binding of a substrate or some a molecules to an enzyme causes a change in the shape of the enzyme so as to enhance or inhibit its activity.
What is a competitive inhibitor?
any molecule that can bind to the active site of an enzyme with sufficient affinity such that it can compete with the enzyme’s natural substrate and reduce enzyme activity as a result.
What is the active site of an enzyme?
the region of an enzyme where substrate molecules bind and undergo a chemical reaction
What is a non competitive inhibitor?
an inhibitor binding to an allosteric site resulting in decreased efficiency of the enzyme
What is an allosteric site?
region of an enzyme that allows activator or inhibitor molecules to bind to the enzyme in order to activate or inhibit enzyme activity
site other than the active site
what is cooperativity in enzymes?
a phenomenon in which the shape of one subunit of an enzyme is altered by the substrate or some other molecule so as to change the shape of a neighbouring subunit.
subunits of the enzyme of cooperating (working together) to change their shape
what do allosteric regulation and cooperativity have in common?
both increase enzyme efficiency as the binding of a molecule induces change in all the enzyme subunits
what is the difference between an allosteric site and an active site?
-allosteric site is a region of an enzyme that allows activator or inhibitor molecules to bind to the enzyme to either activate or inhibit enzyme activity
-an active site is a region of an enzyme where substrate molecules bind and catalyze the reaction resulting in the production of particular products
the difference is in terms of which molecules their sites can bind
what is the allosteric site and cooperativity used for in terms of single and complex enzymes?
allosteric site is for both single enzymes and complex enzymes
cooperativity only works for enzyme complexes
what is the difference between an allosteric site and an cooperativity in terms of substrate molecules?
an allosteric site has only non subtract molecules. cooperativity, occurring at the active site, has substrate molecules
how is an enzyme denatured?
at a certain point, the speed of the reaction drops sharply. At this point, the thermal agitation (small component particles of a substance that is associated with heat) is severe enough to disrupt the bonds within the enzyme that stabilize the active conformation
how does a decrease in temperature slow the rate of a reaction?
when a decrease in temperature occurs, the particles are not moving fast enough to collide with sufficient energy to break the bonds to release the energy needed to catalyze the reaction. therefore a decrease in temperature slows the rate of a reaction
how is the optimal temperature of enzymes significant to the way particles move?
a temperature which allows the highest number of collisions without denaturation
what is the optimal temperature of an enzyme?
human body temperature
As with temperature, most enzymes also have an optimal pH (acidity and basic) in which they function best. Generally a pH of around 6-8 (close to neutral) is preferred. WHY?
Because the major addition or removal of H+ ions can disrupt the bonding necessary to maintain the 3D shape.
why does the increase of substrate increased the rate at which a product is formed?
more substrate molecules will collide with enzyme active sites so more product will be formed
the increase of substrate only occurs up to a maximum value whereby the enzyme becomes saturated with substrate. WHAT DOES THIS MEAN?
Once the enzyme is saturated with the substrate, an increase of substrate will have no effect on the rate of the reaction, because the enzyme is fully covered and will be working at its maximum limit.
what does Km stand for?
the concentration of substrate with the reaction is half the maximum rate
what does a low Km value mean?
the enzyme reaches a maximum catalytic rate at a low substrate concentration
what does a low Km value indicate about how the enzyme binds to the substrate?
the enzyme binds the substrate tightly.
what does a high km value mean?
enzyme catalyzed reaction reaches a maximum rate at a high concentration of substrate
turnover number
the maximum number of substrate molecules converted to product per minute for each active site.
what does a high km value indicate about the enzyme and the substrate?
the enzyme binds to the substrate very loosely
how many substrates does it take to saturate the enzyme in a high km value and why?
it takes a lot of substrates to saturate the enzyme because the enzyme processes the substrate rapidly, it thus has a high turnover number
how many substrates does it take to saturate the enzyme in a low km value and why?
it doesn’t take a lot of substrates to saturate the enzyme because the enzyme processes the substrate more slowly, it thus has a low turnover number
activation energy
the amount of energy that must be put in for a reaction to begin
why does an enzyme-catalyzed reaction increase with an increased concentration of enzyme?
the more enzymes involved in the reaction, the higher number of active sites to catalyze the reaction. the chemical reaction will speed up as long as the active sites are not fully saturated with substrate already
why does the rate of an enzyme-catalyzed reaction increase with an increased concentration of enzyme up to a certain point ?
the chemical reaction will speed up as long as the active sites are not fully saturated with substrate already
what is the relationship between optimal enzyme and substrate concentration?
they are inherently dependent on each other
why are transition energy and activation energy proportional?
catalyst lower the energy of the transition state of a reaction/ since activation energy is the difference between the transition energy and the reactant energy, lowering the transition energy also lowers the activation energy.
what is enzyme denaturation?
when the bonds within the enzyme, either hydrogen, van der waals, ionic of disulfide bridge bonds are disrupted
whats is the exception to the optimal ph of enzymes?
pepsin also known as hydrochloric acids has a pH of 2 and works in the stomach
what is the function of membrane bound compartments? what effect does it have outside the compartment?
separates substrates and enzymes that act upon them into the same compartment. this can increase substrate up to 10 times outside the compartment
what are enzyme complexes?
the assembly of several enzymes into one molecules
what is the function of enzyme complexes?
carry out a single or series of biochemical reactions that take place in the cells
- increase substrate concentration
2.bring enzymes involved in the reaction into large enzyme complexes
- large enzymes
