Enzymes Flashcards
The enzymes that catalyze the conversion of one ormore compounds (substrates) into one or more differ-ent compounds (products) enhance the rates of thecorresponding noncatalyzed reaction by factors of atleast _____. Like all catalysts, enzymes are neither con-sumed nor permanently altered as a consequence oftheir participation in a reaction.
10 raised to the 6th power
________ are biologic polymers that catalyze the chemi-cal reactions which make life as we know it possible.
Enzymes
catalyze oxidations and reduc-tions
Oxidoreductases
Transferases catalyze transfer of groups such asmethyl or glycosyl groups from a donor moleculeto an acceptor molecule.
3. Hydrolases catalyze the hydrolytic cleavage ofCC, CO, CN, PO, and certain otherbonds, including acid anhydride bonds.
4. Lyases catalyze cleavage of CC, CO, CN,and other bonds by elimination, leaving doublebonds, and also add groups to double bonds.
5. Isomerases
catalyze geometric or structuralchanges within a single molecule.
6. Ligases catalyze the joining together of two mole-cules, coupled to the hydrolysis of a pyrophospho-ryl group in ATP or a similar nucleoside triphos-phate.
__________are distinguished by their tight, stableincorporation into a protein’s structure by covalent ornoncovalent forces.
Prosthetic groups
Examples include pyridoxal phos-phate, flavin mononucleotide (FMN), flavin dinu-cleotide (FAD), thiamin pyrophosphate, biotin, andthe metal ions of Co, Cu, Mg, Mn, Se, and Zn.
roughlyone-third of all enzymes that contain tightly boundmetal ions are termed
Metalloenzymes
serve functions similar to those of prostheticgroups but bind in a transient, dissociable manner ei-ther to the enzyme or to a substrate such as ATP
Cofactors
serve as recyclable shuttles—or grouptransfer reagents—that transport many substrates fromtheir point of generation to their point of utilization.
Coenzymes
Otherchemical moieties transported by coenzymes includemethyl groups (folates), acyl groups (coenzyme A), andoligosaccharides (dolichol).
water-soluble Vitamin __ supply important compo-nents of numerous coenzymes.
Vitamin B
Niacin and riboflavin form NAD and NADP and FMN and FAD, respectively.Pantothenic acid is a component of the acyl group car-rier coenzyme A. As its pyrophosphate, thiamin partici-pates in decarboxylation of α-keto acids and folic acidand cobamide coenzymes function in one-carbon me-tabolism.
involves the formationof a covalent bond between the enzyme and one or moresubstrates.
Covalent catalysis
drawback wasaddressed by Daniel Koshland’s _______,which states that when substrates approach and bind toan enzyme they induce a conformational change, achange analogous to placing a hand (substrate) into aglove (enzyme)
Induced fit theory
______ ARE DISTINCT ENZYMEFORMS THAT CATALYZE THE
SAME REACTION
Isozymes
_______ is the field of biochemistry concernedwith the quantitative measurement of the rates of en-zyme-catalyzed reactions and the systematic study of fac-tors that affect these rates
Enzyme kinetics
The _______ describes both the direc-tion in which a chemical reaction will tend to proceedand the concentrations of reactants and products thatwill be present at equilibrium.
Gibbs free energy change ∆G (also called either thefree energy or Gibbs energy)
The _______—of chemical kinetics states that for two molecules toreact they must (1) approach within bond-forming dis-tance of one another, or “collide”; and (2) must possesssufficient kinetic energy to overcome the energy barrierfor reaching the transition state
kinetic theory—also called the collision theory
Raising the temperature increases the kinetic energy ofmolecules. the total num-ber of molecules whose kinetic energy exceeds the en-ergy barrier Eact (vertical bar) for formation of productsincreases from low (A), through intermediate (B), tohigh (C) temperatures. Increasing the kinetic energy ofmolecules also increases their motion and therefore thefrequency with which they collide. True or false?
True
