Upgrade to remove ads
Terms in this set (47)
How do enzymes speed up metabolic reactions?
by lowering energy barriers
What is an enzyme
a macromolecule that acts as a catalyst
what is a catalyst
an agent that speeds up a reaction without being consumed, and can be used multiple times
what are enzymes primarily composed of
proteins, however some RNA molecules called ribozymes can also function as ribosomes
what is an example of an enzymatic reaction
Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme catalyzed reaction
what is the activation energy
the energy required to contort the reactant molecules so that the bonds can break (the amount of energy needed to push the reactants to the top of the energy barrier so that that new bonds can be formed after.)
what is activation energy often supplied by
in the form of heat
when the molecules have absorbed enough energy for the bonds to break causing the reactant to be in a very unstable condition
explain the energy profile of an exergonic reaction
in the uphill portion of the graph is the activation energy increasing, as activation energy increases so does the free energy. when the peak of the graph when activation energy has been completely absorbed, the reactants are in a transition state where the reactant are active and their bonds can be broken. as the bonds break now bonds are formed thus making the reaction more stable, lowering free energy and the activation energy is released usually in the form of heat again.
how do enzymes speed up reactions
they speed up reactions by lowering the activation energy barrier so that the reactant molecules can absorb enough energy to to reach the transition state even at moderate temperatures.
do enzymes change free energy
no they just hasten reactions that would already occur
what is a substrate
the reactant an enzyme acts on, an enzyme binds to its substrate(s)
what is an enzyme-substrate complex
an enzyme binds to its substrate(s) forming a complex
what reaction occurs when an enzyme and substrate bind
enzyme+substrate --> enzyme-substrate complex --> Enzyme+ products
example of enzyme sucrase binding to sucrose
sucrase+sucrose+water --> sucrase-sucrose-water complex --> sucrase+glucose+fructose
what do most enzymes end with
how can enzymes detect such specific substrates
most enzymes are proteins that have different shapes witch results in specificity (the shape of the enzyme is very specific)
only a region of the enzymes binds to the substrate which is called the active site and is typically a pocket or groove on the surface
some enzymes bind more than one substrate at a time
what is induced fit and how is it beneficial
occurs when a substrate binds, and it brings chemical groups of the enzyme's active site into positions that enhance their ability to catalyze the reaction.
what happens as the substrate enters the active site on an enzyme
the enzyme changes shape slightly due to interactions between the substrate's chemical groups and the the chemical groups on the side chains of the amino acids in the enzyme. this shape change makes the active site fit more snug around the substrate
what holds the substrate in the enzyme
weak hydrogen bonds and ionic bonds
when looking at metabolism can enzymes only speed a reaction or do they have the ability to reverse a metabolic reaction
they can reverse a reaction depending of the sign of free energy
what ways can the active site in enzymes lower activation energy and thus speed up reactions
Orienting substrates correctly, Straining substrate bonds, Providing a favorable microenvironment, Covalently bonding to the substrate (transiently)
what effect would increasing the ratio of substrate to enzyme have of the rate at which the enzyme converts substrate to product
the rate would increase, because the more substrate molecules available the more frequently they access the active sites of the enzyme molecules.
define saturated in terms of the rate at which the enzyme converts substrate to product
as soon as a product leaves the active site another substrate molecule enters. the rate of the reaction is determined by the speed at which the active sites converts substrate to products
what are the five steps to The active site and catalytic cycle of an enzyme
1. the substrates enter the active site
2. substrates are held in the active site by weak interactions
3. substrates are converted into products
4. products are released
5. active site is available for new substrates
what are the local conditions that effect enzyme activity
temp and pH
how does temp effect enzyme activity
up to a point the rate of an enzymatic reaction increases as temp increases (partly bc substrates collide with active sites more frequently when the molecules move rapidly) however the speed of an enzymatic reaction drop sharply once the temp rises above the optimal temp. once the temp increases to a certain point the bonds that hold substrates into the enzyme at the active site begin to break and the protein molecule eventually denatures.
how does pH effect enzymatic activity
like temp there is an optimal pH at which an enzyme is most active. the optimal range for enzymes to function in is usually 6-8 however the digestive enzyme in the stomach has an optimal pH of 2. this acidic environment would denature other enzymes however the stomach enzyme has adapted
what are cofactors
many enzymes require nonprotein helpers for catalytic activity, these are called cofactors, and they are chemicals that specifically influence the enzyme (non-protein enzyme helpers)
what is a cofactor referred to if it is an organic molecule and give examples
coenzyme; vitamins- the act as coenzymes or raw materials from which coenzymes are made.
what are the two types of enzyme inhibitors
competitive and noncompetitive
explain the difference between the two enzyme inhibitors
Competitive inhibitors bind to the active site, competing with the substrate
Noncompetitive inhibitors bind to another part of an enzyme, causing it to change shape and making the active site less effective
many spontaneous reactions occur very slowly. why don't all spontaneous reactions occur instantly?
a spontaneous reaction is exergonic, however if it has a high activation energy that is rarely attained the rate of the reaction may be low.
why do enzymes act only on specific substrates
bc only the specific substrate will fit correctly into the active site of the enzyme which carries out the catalyst
malonate is an inhibitor of the enzyme succinate dehydrogenase. how would you determine whether malonate is a competitive on noncompetitive inhibitor?
in the presence of malonate increase the concentrations of the normal substrate (succinate) and see whether the reaction increases or not. if the reaction increases then malonate is the competitive inhibitor
how does a cell regulate enzyme activity that controls metabolism
by switching on or off genes that encode specific enzymes, or by regulating the activity of enzymes
wat is allosteric regulation
used to describe any case in which a proteins function at one site is affected y the binding of a regulatory molecule to a separate site (when a regulatory molecule binds to a protein at one site (allosteric site) which affects the protein's function at another site)
what does the binding of an activator to regulatory site stabilize
active form of the enzyme
what does the binding of an inhibitor to a regulatory site stabilize
inactive form of the enzyme
what is cooperativity
another type of allosteric activation is a substrate binding to one active site in the multi-subunit enzyme triggers a shape change in all subunits thereby increasing catalytic activity at the other active sites. this mechanism amplifies the response of enzymes to substrates.
what is feedback inhibition
a metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway
how does feedback inhibition help
prevents a cell from wasting chemical resources by synthesizing more product than needed
localization of enzymes within the cell
structures within the cell can promote metabolic transformations, and can help bring order to metabolism. cellular structures help bring order to metabolic pathways.
how does an activator and an inhibitor have different effects of an allosterically regulated enzyme?
the activator binds in such a way that it stabilizes the active form of an enzyme whereas the inhibitor stabilizes the inactive form
what is a catalyst
THIS SET IS OFTEN IN FOLDERS WITH...
Biology Ch. 11 Mastering
AP Bio cell signaling nervous system
YOU MIGHT ALSO LIKE...
Ch 8 Part
AP Bio 8.4
Bio 121 Chapter 8: Enzymes and metabolism
Lesson 10 Enzymes
OTHER SETS BY THIS CREATOR
Exam 3 Concepts
Exam 2 concepts
Exam 1 concepts