Enzymes Flashcards
what is a chemical reaction?
a chemical reaction is a process that either forms or breaks the chemical bonds that hold atoms together. dehydration synthesis or hydrolysis.
all chemical reactions either?
release energy or require an input of energy.
what is a reaction that releases energy called?
its called an exergonic reaction. this means the reactants contain more energy than the products.
what is a reaction that requires an input of energy called?
its called an endergonic reaction. this means that the products contain more energy than the reactants.
every chemical reaction requires?
an initial investment of energy.
for every reaction there is a specific?
activation energy that needs to be present: amount of initial energy that is required in order for the reactant molecules to contort so the bonds can break.
where does the initial activation energy come from?
ea is often supplied in the form of heat that the reactants absorb from the environment. this heat causes the reactants to move more quickly so that they collide more often. the collisions also make the bonds more ready to break.
once enough energy is absorbed so that the bonds can break…?
the ea has been met.
what determines the rate of the reaction?
the activation energy
for some chemical reactions the ea is low…?
low enough that they can proceed at room temperature in a short time.
for some chemical reactions, the ea is high…?
high and at room temperature, the reaction may proceed at an unnoticeable rate.
is the sucrose=glucose+fructose reaction fast or slow at room temperature?
it is very slow at room temperature.
if reactions are to proceed at reasonable rates…?
one would have to increase the proportion of molecules that have enough energy. this can be done by? heating and decreasing the ea.
heating? and problems?
heating can kill cells and would not be specific: all chemical reactions would speed up.
decreasing the ea?
by decreasing the ea, one will ensure that a greater proportion of molecules will collide in order for the reaction to occur.
the ea can be decreased how?
by the use of a catalyst. in biological systems a catalyst is called an enzyme. an enzyme is a protein.
do enzymes change the reaction?
no, they do not change the reaction in any way, they just speed up the reaction.
what is the effect of enzymes on reaction rate?
enzymes lower the ea: less collisions need to happen in order for the transition state to be reached.
what is the substrate?
the substrate is the reactant an enzyme acts on.
enzymes are?
- specific
- enzymes bind to its substrate forming an enzyme substrate complex
what is the active site?
region on the enzyme where the substrate binds.
what is an induced fit?
the shape of the enzyme changes slightly when the substrate enters. this is due to the interactions that occur between the chemical groups of the substrate and the amino acids that make up the active site.
how does the active site lower the ea barrier?
by orienting the substrates correctly to help the reaction occur, straining substrate bonds, providing a microenvironment that is favorable for the reaction to occur, may itself directly participate in the chemical reaction.
an enzymes activity is affected?
by general environmental factors.
each enzyme has?
an optimal temperature in which it functions and has an optimal pH in which it can function.
what happens to an enzyme if the environmental conditions change?
protein becomes denatured and it is biologically inactive.
what are cofactors?
many enzymes require cofactors for activity.
- they are not made of protein
what are some inorganic cofactors?
metal atoms such as zinc, copper, iron.
what are some organic cofactors?
organic cofactors are called coenzymes.
- most vitamins are coenzymes
- these cofactors may be bound permanently to the enzyme or may bind loosely and reversibly with the substrate.
an enzymes activity can be?
inhibited.
what are irreversible inhibitors?
inhibitors that bind to the enzyme via a covalent bond.
examples: toxins, poisons
what is a reversible inhibitor?
inhibitors that bind to the enzyme via weak interactions.
- they can be competitive or noncompetitive.
what is a competitive inhibitor?
competitive inhibitors bind to the active site of an enzyme, competing with the substrate.
CAN BE OVERCOME BY INCREASING SUBSTRATE CONCENTRATION.
what is a noncompetitive inhibitor?
noncompetitive inhibitors bind to a site other than the active site.
- binding changes the conformation of the enzyme which interferes with the function of the active site.
- also called allosteric regulation.
CANT BE OVERCOME BY INCREASING SUBSTRATE CONCENTRATION.
the inhibition of en enzyme activity is?
a normal process that happens in cells.
- used to control the enzymes involved in cellular metabolism.
what is feedback inhibition?
the end product of a metabolic pathway shuts down the pathway by inhibiting an enzyme found in the beginning of the pathway.
