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Microbiology, 5/e

Lansing M Prescott, Augustana College
Donald A Klein, Colorado State University
John P Harley, Eastern Kentucky University

Metabolism: Energy, Enzymes, and Regulation

Self-Quiz


1	Which compound is being reduced in this reaction?
		A)	Pyruvate
		B)	Lactate
		C)	NAD+
		D)	NADH+H+
		E)	Not enough information to tell


2	Which compound is being oxidized in this reaction??
		A)	Pyruvate
		B)	Lactate
		C)	NAD+
		D)	NADH+H+
		E)	Not enough information to tell


3	Which of the following is/are true about enzymes I. All enzymes are proteins. II. All proteins are enzymes.
		A)	I only is true.
		B)	II only is true.
		C)	Both I and II are true.
		D)	Neither I nor II are true.


4	If the Keq for an enzymatic reaction is greater than 1, I. the reaction will be endergonic. II. the reaction cannot occur without the input of energy.
		A)	I only is true.
		B)	II only is true.
		C)	Both I and II are true.
		D)	Neither I nor II are true.


5	A complex enzyme is broken down into its constituent parts: apoenzyme and cofactor. Portions of the separate parts are heated for 3 minutes at 100°C. Various combinations are tested for their ability to perform the enzymatic function. Which of the following combinations would still be functional?
		A)	Unheated apoenzyme and heated cofactor
		B)	Heated apoenzyme and heated cofactor
		C)	Unheated apoenzyme and unheated cofactor
		D)	Heated apoenzyme and unheated cofactor
		E)	More than one of the above combinations would function.


6	An enzyme that is always produced, regardless of the presence of substrates or the end products, is called
		A)	a constitutive enzyme.
		B)	an isoenzyme.
		C)	a repressible enzyme.
		D)	an allosteric enzyme.
		E)	a regulator enzyme.


7	About 7.3 kcal/mole are released when
		A)	NAD⁺ is reduced to NADH.
		B)	ATP hydrolysis is coupled to sucrose synthesis.
		C)	the terminal phosphate bond of ATP is broken by hydrolysis.
		D)	a phosphoester bond of ATP is formed.
		E)	glucose is converted to CO₂ and H₂O.


8	In the following reaction, which component is being reduced? C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O + energy
		A)	C₆H₁₂O₆
		B)	O₂
		C)	CO₂
		D)	H₂O
		E)	energy


9	In the following reaction, which component is being oxidized? C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O + energy
		A)	C₆H₁₂O₆
		B)	O₂
		C)	CO₂
		D)	H₂O


10	Adenosine triphosphate is a type of
		A)	fatty acid.
		B)	amino acid.
		C)	enzyme.
		D)	steroid.
		E)	nucleotide.


11	A substrate binds to its enzyme at a location called the ______ site.
		A)	coenzyme
		B)	substrate
		C)	active
		D)	polypeptide
		E)	cofactor


12	The vitamin niacin is part of the ______ molecule.
		A)	ferredoxin
		B)	iron-sulfur
		C)	pyridoxal phosphate
		D)	pyrophosphate
		E)	NAD⁺


13	Denaturation of an enzyme refers to the
		A)	proper arrangement of the enzyme in a metabolic pathway.
		B)	improper arrangement of the enzyme in a metabolic pathway.
		C)	loss of the enzyme's proper shape.
		D)	formation of the enzyme's proper shape.
		E)	formation of a new isozyme for that enzyme.


14	ATP is required to do
		A)	chemical work.
		B)	transport work.
		C)	mechanical work.
		D)	all of the above types of work.
		E)	none of the above, another compound provides the necessary energy.


15	The ability of Vibrio fischeri to convert chemical energy directly into radiant energy in bioluminescence is an example of __?___ at work.
		A)	Shelford's law of tolerance
		B)	Leibig's law of the minimum
		C)	the first law of thermodynamics
		D)	Heisenberg's principle of uncertainty
		E)	the third law of thermodynamics


16	An exergonic reaction is one that
		A)	requires energy in order to proceed.
		B)	releases energy for work.
		C)	gives off much heat.
		D)	wastes energy.
		E)	none of the above, there is no such thing as an exergonic reaction.


17	An endergonic reaction is one that
		A)	requires energy in order to proceed.
		B)	releases energy for work.
		C)	gives off much heat.
		D)	wastes energy
		E)	none of the above, there is no such thing as an endergonic reaction.


18	The reaction A + B -------> AB takes place slowly at 20°C unless either compound X or Y is present. Compound X is a metallic catalyst for the reaction and Y is an enzyme which catalyzes the reaction. Ten ml of solution A and B is placed in each of four test tubes to which varying amounts of X or Y are added as follows. If A and B are heat stable at 100°C and the reaction occurs at that temperature, the reaction is probably
		A)	greatest in tube I.
		B)	greatest ln tube II.
		C)	greatest in tube III.
		D)	greatest in tube IV.
		E)	equal in all tubes.


19	The vitamin riboflavin is part of the ______ molecule.
		A)	ferredoxin
		B)	FAD
		C)	pyridoxal phosphate
		D)	pyrophosphate
		E)	NAD⁺


20	Hydrogen and oxygen release enormous amounts of energy when they react -- witness the Hindenberg explosion. Yet, hydrogen and oxygen can be mixed together in a balloon and nothing will happen. Why?
		A)	Competitive inhibitors are blocking the reaction from occurring in the active site.
		B)	There must be contaminating elements in the balloon that prohibit the reaction from occurring.
		C)	The energy of activation to form the transition-state complex is too high to allow the reaction to occur without assistance.
		D)	The person mixing the oxygen and hydrogen in the balloon must have done something wrong.
		E)	The transition-state complex has too low an energy barrier.


21	The fact that beta-oxidation (breakdown) of fatty acids occurs in the mitochondria whereas fatty acid synthesis occurs in the cytoplasmic matrix is an example of regulation of enzymatic activity by the __?__ mechanism.
		A)	compartmentation
		B)	induction
		C)	repression
		D)	competitive inhibition
		E)	non-competitive inhibition


22	Compare the entities I and II I. The affinity of an enzyme for its substrate when the enzyme has a Km of 0.50M. II. The affinity of an enzyme for its substrate when the enzyme has a Km of 0.05M.
		A)	I is greater than II.
		B)	II is greater than I.
		C)	I is exactly or approximately equal to II.
		D)	I may stand in more than one of the above relations to II.


23	Compare the entities I and II I. The ability of a competitive inhibitor to bind to an active site in an allosterically controlled enzyme. II. The ability of a non-competitive inhibitor to bind to an active site in the same allosterically controlled enzyme.
		A)	I is greater than II.
		B)	II is greater than I.
		C)	I is exactly or approximately equal to II.
		D)	I may stand in more than one of the above relations to II.


24	Compare the entities I and II I. The ability of NADH+H⁺ to be reduced. II. The ability of NAD⁺ to be reduced.
		A)	I is greater than II.
		B)	II is greater than I.
		C)	I is exactly or approximately equal to II.
		D)	I may stand in more than one of the above relations to II.


25	Compare the entities I and II I. The ability of FADH to be oxidized. II. The ability of FAD to be oxidized.
		A)	I is greater than II.
		B)	II is greater than I.
		C)	I is exactly or approximately equal to II.
		D)	I may stand in more than one of the above relations to II.


26	Compare the entities I and II I. The V_max of an enzyme without a competitive inhibitor II. The V_max of an enzyme with a competitive inhibitor
		A)	I is greater than II.
		B)	II is greater than I.
		C)	I is exactly or approximately equal to II.
		D)	I may stand in more than one of the above relations to II.


27	To a living organism, which of the following has the greatest amount of available energy per molecule?
		A)	ATP
		B)	ADP
		C)	AMP
		D)	H₂O
		E)	CO₂


28	The reaction A + B -------> AB takes place slowly at 20°C unless either compound X or Y is present. Compound X is a metallic catalyst for the reaction and Y is an enzyme which catalyzes the reaction. Ten ml of solution A and B is placed in each of four test tubes to which varying amounts of X or Y are added as follows. If A and B are heat stable at 20°C and the reaction occurs at that temperature, the reaction is probably
		A)	greatest in tube I.
		B)	greatest ln tube II.
		C)	greatest in tube III.
		D)	greatest in tube IV.


29	Which of the following is the best evidence for the lock and key theory of enzyme action?
		A)	All isolated enzymes have been identified as proteins.
		B)	Compounds similar in structure to the substrate inhibit enzyme activity.
		C)	Enzymes are found in living organisms and speed up certain reactions.
		D)	Enzymes speed up reactions by definite amounts.
		E)	Enzymes determine the direction of a reaction.


30	The ability of CTP to bind to aspartate carbamoyltransferase and shut down the synthesis of more CTP is an example of
		A)	enzyme induction.
		B)	enzyme repression.
		C)	feedback inhibition of enzyme activity.
		D)	channeling.
		E)	compartmentation.

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