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119 Cards in this Set
- Front
- Back
The substance that undergoes a chemical change catalyzed by an enzyme. |
substrate |
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The inactive precursor of an enzyme. |
zymogen |
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A non protein molecule required by an enzyme for catalytic activity. |
cofactor |
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A slightly different form of the same enzyme. |
isoenzyme |
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The location on an enzyme where catalysis occurs. |
active site |
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An enzyme with quaternary structure with specific modulator binding sites. |
allosteric enzyme |
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An inactivated enzyme formed by the removal of the cofactor. |
apoenzyme |
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As the concentration of ATP increases in a cell, it decreases the turnover number of citrate synthetase. In this case, ATP acts as a(n) |
modulator |
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The graph above is a generalization. What factor could be changed (increased) to produce the graph above showing the rate of enzyme activity? |
enzyme concentration |
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An enzyme-substrate solution at p H 1 shows no product formation. Slowly increasing the p H from p H 1 to p H 14 still does not show any sign of enzyme activity. This is most likely because |
the enzyme has been denatured |
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What would be an appropriate name for an enzyme that catalyzes the hydrolysis of fumarate? |
fumarase |
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Enzymes catalyze only certain reactions involving certain substances. This general characteristic is called. --BLANK. |
catalytic efficiency |
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What best accounts for the fact that many enzymes only act as catalysts for one specific reaction? |
the lock-and-key theory |
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The number of molecules of substrate acted upon by one enzyme molecule in one minute is called the |
turnover number |
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What factor could be changed (increased) to produce the graph above showing the rate of enzyme activity? |
substrate concentration |
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Heavy metal ions are believed to act as.---blank. inhibitors of enzymes. |
irreversible |
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An enzyme was poisoned by an inhibitor, but increasing the concentration of the substrate was found to return most of the enzyme's function. This is an example of what specific type of enzyme inhibition? |
competitive |
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Enzymes speed up chemical reactions by |
reducing activation energies |
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An analysis of isoenzymes in blood serum can be used to |
diagnose disease |
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With the exception of a few RNA molecules all enzymes are .---BLANK. |
globular proteins |
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To what family of biomolecules does the majority of enzymes belong? |
proteins |
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An enzyme is a biomolecule that catalyzes.---BLANK. |
chemical reactions |
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Biomolecules which catalyze chemical reactions are called.---blank. |
enzymes |
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Enzymes are well suited to their essential roles in living organisms in three major ways: They have enormous catalytic power, they are highly specific in the reactions they catalyze, and their activity as catalysts can be.---Blank. |
regulated |
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Three important characteristics of enzymes are high catalytic power, specificity, and that their activity can be .---blank. |
regulated |
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Enzymes are true catalysts that speed chemical reactions by lowering activation energies, allowing reactions to achieve .---blank. more rapidly |
equilibrium |
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Enzymes speed up reactions by lowering .---blank. |
activation energies |
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Enzymes are often quite specific in the type of reaction they catalyze and even the particular substance that will be involved in the reaction. This important characteristic is called .---blank. |
specificity |
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What term is used to describe the characteristic that enzymes catalyze only certain reactions? |
specificity |
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The catalyzing of the reaction of one and only one substance is called.---blank. |
absolute specificity |
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The enzyme urease which acts upon only one substance is called? |
absolute specificity |
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.---BLANK. is exhibited by enzymes catalyzing the reaction of structurally related substances. |
Relative specificity |
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Proteases, enzymes which can hydrolyze substances belonging to the family of proteins, exhibit .---blank. specificity. |
relative |
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Stereochemical specificity extends to .---blank.: D-amino acid oxidase will not catalyze the reactions of L-amino acids. |
enantiomers |
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The characteristic of an enzyme that it catalyzes a reaction of only one or a pair of stereoisomers is called .---blank. specificity. |
sterochemical |
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The earliest discovered enzymes were given names ending with .---blank. to indicate their protein composition. A systematic nomenclature system known as the International Enzyme Commission (IEC) system groups enzymes into six classes and assigns each enzyme a specific name. |
–in |
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What name is given to the systematic nomenclature system for enzymes? |
International Enzyme Commission System |
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How many major classes of enzymes are designated by the systematic nomenclature system? |
six |
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Enzymes are assigned convenient common names with the ending .---blank. |
–ase |
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A chemical substance can often be identified as an enzyme by the ending .---blank. in the name. |
-ase |
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A .---blank. will remove hydrogens from a compound. |
dehydrogenase |
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The substance that undergoes a chemical change catalyzed by an enzyme is called the .---blank. |
substrate |
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The substance acted upon by the enzyme urease is .---blank. |
urea |
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Some common names indicate both the substrate and type of .---blank.. For example, alcohol dehydrogenase specifies a dehydrogenation (removal of hydrogen) from an alcohol. |
reaction |
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What is the substrate for the enzyme lactate dehydrogenase? |
lactate |
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A number of hereditary diseases appear to result from the absence of enzymes or from the presence of altered enzymes. These diseases are often referred to as .---blank. of metabolism. |
inborn errors |
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A disease in which a genetic change causes a deficiency of a particular enzyme is called an .---blank. error of metabolism. |
inborn |
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Nonprotein molecules or ions, weakly bound to an enzyme, and yet required by an enzyme for catalytic activity are called .---blank.. |
cofactors |
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The enzyme carbonic anhydrase functions only when Zn2+ ion is present. Zn2+ ion is an example of an enzyme .---blank.. |
cofactor |
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A number of metal ions are required in our diet for good health because they are essential for proper enzyme function as .---blank. |
cofactors |
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A number of minerals are important components in our diet because the metal ions serve as enzyme .---blank. |
cofactors |
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When the cofactor is an organic substance, it is called a .---blank. |
coenzyme |
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Because NAD+, a cofactor for the enzyme lactate dehydrogenase, is organic, it may also be referred to as a .---blank. |
coenzyme |
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The protein portion of enzymes requiring a cofactor is called the apoenzyme. The combination of an apoenzyme and cofactor produces an.--blank. |
Apoenzyme + cofactor (coenzyme or inorganic ion) = active enzyme |
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If an active enzyme is stripped of its cofactor, the protein portion remaining is called the .---blank. |
apoenzyme |
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A number of coenzymes are formed in the body from vitamins. For example, the coenzyme NAD+ is formed from the vitamin precursor .---blank. |
nicotinamide |
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What substances does the body use to synthesize cofactors? |
vitamins |
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What substance is a precursor for NAD+? |
nicotinamide |
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The region of an enzyme where the substrate and enzyme interact is called the .---blank. |
active site |
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The location on an enzyme where a substrate is bound and catalysis occurs is called the .---blank. |
active site |
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The complex formed when a substrate and an enzyme bond is called the enzyme – substrate (ES) complex . As the complex forms, the lock-and-key theory proposes that a specific substrate has a shape fitting that of the enzyme’s.---blank., as a key fits a lock. |
active site |
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The combination formed when substrate and enzyme bond is called the enzyme – substrate .---blank. |
complex |
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What theory proposes that only specific substrates “fit” a given enzyme and can form combinations with it? |
lock-and-key theory |
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A modification of the lock-and-key theory known as the .---blank. proposes that enzymes have a somewhat flexible conformation that may adapt to incoming substrates |
fit theory |
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What theory proposes that the conformation of an enzyme changes to accommodate an incoming substrate? |
induced-fit theory |
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Enzyme activity refers in general to the.---blank. of an enzyme to increase the rate of a reaction. |
catalytic ability |
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The rate at which an enzyme catalyzes a reaction is termed enzyme .---blank. |
activity |
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The experiments which measure rates of enzyme-catalyzed reactions are called enzyme .---blank. |
assays |
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The turnover number for an enzyme is the number of molecules of .---blank. acted upon by one molecule of enzyme per minute. |
substrate |
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One molecule of carbonic anhydrase converts 36 million molecules of carbon dioxide to carbonic acid per minute. The number 36 million is known as the .---blank. number. |
turnover |
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An .---blank. (IU) is a quantity of enzyme that catalyzes the conversion of 1 μ mol of substrate per minute. |
enzyme international unit |
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An enzyme IU (international unit) is an amount of enzyme that converts one .---blank. of substrate per minute. |
μ mol |
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Several factors affect the rate of enzyme-catalyzed reactions. When enzyme concentration is increased, the rate of a reaction .---blank. in a directly proportional way |
increases |
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What type of line is produced when enzyme concentration is plotted versus reaction rate? |
straight |
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When substrate concentration is increased, the reaction rate initially increases and then levels out at a maximum velocity (V max) as all the active sites become .---blank. with substrate |
saturated |
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A maximum velocity is achieved by increasing substrate concentration until the enzyme is .---blank. |
saturated |
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.---blank. have rates that increase with temperature, reach a maximum at the optimum temperature, and then decline as the enzyme is denatured. The optimum temperature usually falls in the range of 25-40oC. |
Enzyme-catalyzed reactions |
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The temperature at which enzyme activity is highest is called the .---blank. temperature. |
optimum |
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Enzymes are usually most effective in a narrow pH range and are less active at pH values lower or higher than this optimum p H. Many enzymes have an .---blank. pH near 7, the pH of most biological fluids. pH's above or below the optimum will denature the protein. |
optimum |
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The pH at which enzyme activity is highest is called the .---blank. pH. |
optimum |
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An enzyme .---blank. is any substance that can decrease the rate of an enzyme-catalyzed reaction. |
inhibitor |
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A substance that decreases the activity of an enzyme is called an enzyme .---blank. |
inhibitor |
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Enzyme inhibitors are classified into two categories: .---blank. |
reversible and irreversible. |
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The two categories of enzyme inhibitors are reversible and .---blank. |
irreversible |
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An .---blank. forms a covalent bond with the enzyme and renders it inactive. |
irreversible inhibitor |
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Cyanide is an example of an .---blank. enzyme inhibitor. |
irreversible |
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Cyanide is toxic because of its impact on the enzyme .---blank. oxidase. |
cytochrome |
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Penicillins belong to a family of compounds that inhibit .---blank., an enzyme that is important in bacterial cell wall construction. |
transpeptidase |
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Compounds, like penicillins, have the ability to prevent bacterial growth and can be referred to as .---blank.. |
antibiotics |
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Penicillin acts as an .---blank.inhibitor. |
irreversible |
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A reversible inhibitor reversibly binds to an enzyme. There are two types of reversible inhibitors: .---blank. |
competitive and noncompetitive |
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The two categories of reversible inhibitors are competitive and .---blank.. |
noncompetitive |
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A .---blank. binds to the active site of an enzyme and thus “competes” with substrate molecules for the active site. |
competitive inhibitor |
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An enzyme inhibitor that competes with substrate for binding at the active site is referred to as a .---blank.inhibitor. |
competitive |
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Sulfa drugs are examples of .---blank. enzyme inhibitors. |
competitive |
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.---blank. can be reversed by increasing the concentration of substrate. The competition between inhibitor and substrate is won by whichever molecular species is in greater concentration. |
Competitive inhibition |
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The effect of a competitive inhibitor can be reversed by adding .---blank. to the reaction. |
substrate |
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A .---blank. bears no resemblance to the normal substrate and binds reversibly to the surface of an enzyme at a site other than the active site |
noncompetitive inhibitor |
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If a reversible inhibitor binds to an enzyme at a location other than the active site, is it a competitive or noncompetitive inhibitor? |
noncompetitive |
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Unlike competitive inhibition, noncompetitive inhibition cannot be .---blank.by the addition of more substrate. |
reversed |
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Is competitive or noncompetitive enzyme inhibition affected by increasing substrate concentration? |
competitive |
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A common mechanism for regulating enzyme activity is the synthesis of enzymes in the form of inactive precursors called .---blank. or .---blank.. When the active enzyme is needed, a stored zymogen is released and activated at the location of the reaction. |
zymogens proenzymes |
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The inactive precursor of an enzyme is called a ________. |
zymogen or proenzyme |
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A second method of enzyme regulation involves modulators, substances that bind to an enzyme at a location other than the active site; they may .---blank.the activity (activators) or .---blank.the activity (noncompetitive inhibitors). |
increase decrease |
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Substances that can bind to an enzyme and increase or decrease the activity are called .---blank.. |
modulators |
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Modulators which increase the activity of an enzyme are called .---blank.. |
activators |
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Enzymes that have a quaternary protein structure with distinctive binding sites for modulators are referred to as .---blank. enzymes. |
allosteric |
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An enzyme whose activity is regulated by the binding of modulators is called an .---blank. enzyme. |
allosteric |
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The type of allosteric regulation in which the enzyme that catalyzes the first step of a series of reactions is inhibited by the final product is called .---blank.. |
feedback inhibition |
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A process in which the end product of a sequence of enzyme-catalyzed reactions inhibits an earlier step in the process is called .---blank. inhibition. |
feedback |
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A third method of controlling the level of enzyme activity involves enzyme .---blank., the synthesis of enzymes in response to a temporary need of the cell. |
induction |
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The synthesis of an enzyme in response to a cellular need is called enzyme .---blank.. |
induction |
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Changes in blood serum concentrations of specific enzymes can be used clinically to detect cell damage and even to suggest the site of the damage. .---blank., slightly different forms of the same enzyme produced by different tissues, are particularly useful in clinical diagnosis. |
Isoenzymes |
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What name is given to slightly different forms of the same enzyme produced by different tissues? |
isoenzyme |
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Lactate dehydrogenase (LDH) and creatine kinase (CK) are two enzymes which exist in .---blank. Because of the wide range of tissue distribution of LDH isoenzymes, serum levels of LDH are used in the diagnosis of a number of diseases. |
multiple forms. |
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Two examples of isoenzymes are CK and .---blank.. |
LDH |
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An assay for the isoenzyme .---blank. makes a good initial diagnostic test because of the enzyme's wide distribution. |
LDH |
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The enzyme acid phosphatase is useful in diagnosing cancer of the .---blank.. |
prostate |
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The pathological condition of hepatitis may be diagnosed using an assay for alanine .---blank.. |
transaminase |