Deck 10: Introduction to Metabolism

Question 1

The flow of material through a metabolic pathway is called the ________.

A)current
B)degree of amplification
C)cascade effect
D)flux

Answer 1

flux

Question 2

The percent of genomes involved in intermediary and energy metabolisms in a wide variety of species is about

A)10%.
B)15-30%.
C)20-50%.
D)30% or more.

Answer 2

15-30%.

Question 3

Phosphorylation at the expense of ATP is catalyzed by ________.

A)protein kinases
B)phosphoryl isomerases
C)phosphatases
D)All of the above

Answer 3

protein kinases

Question 4

The evolution of biochemical pathways can be studied by

A)isolating pathway enzymes from different individuals.
B)comparing pathways in closely related species.
C)comparing pathways in many diverse bacteria.
D)comparing linear and circular pathways.

Question 5

Which statement does not explain why many biochemical processes are carried out via multi-step pathways rather than by single-step reactions (or only a few steps)?

A)Multi-step pathways allow for more control points to regulate biochemical processes.
B)The end products of most pathways can usually be produced only by the pathway reactions that nature has evolved.
C)Sharing of intermediates between pathways is facilitated this way.
D)There is greater control over the amounts of energy that are consumed or released at any one time.

Question 6

Metabolic pathways that involve the degradation of large molecules to smaller ones are classified as ________.

A)anabolic
B)catabolic
C)amphibolic
D)intermediary

Question 7

Intermediary metabolism is the term applied to reactions that ________.

A)degrade molecules
B)synthesize large molecules such as proteins
C)convert glucose to pyruvate
D)involve low molecular weight metabolites

Question 8

Ten people are sitting in a row.Their objective is to whisper a secret from one person to the next all the way down the row.The first person whispers the secret to the second person who passes the secret to the third person and so on.After whispering to the third person,the second person in the row notices the ninth person has fallen asleep in their chair,so she gets up,goes down the row and shakes person nine awake.This example is similar to ________.

A)allosteric control
B)positive cooperativity
C)feed-forward activation
D)negative modulation

Question 9

Bacteria that degrade oil at great depths in offshore waters have most likely evolved new pathways and ________ by modifying existing ones.

A)DNA
B)duplicate factors
C)cofactors
D)enzymes

Question 10

The flow of material through a reaction pathway usually depends on ________.

A)control at several steps in the pathway
B)control of the first step of the pathway
C)covalent modification of the enzyme that catalyzes the reaction
D)feed-forward activation

Question 11

The glycolytic pathway oxidizes glucose to two molecules of pyruvate and also produces a net of two molecules of ATP.ATP allosterically inhibits the enzyme,PFK-1,that catalyzes the third step of glycolysis.This is an example of ________.

A)feed-forward activation
B)feedback inhibition
C)negative cooperativity
D)competitive inhibition

Question 12

Which statement is not true about catabolic pathways?

A)They have a net release of energy.
B)They have a net consumption of ATP.
C)They liberate smaller molecules from larger ones.
D)They include the citric acid cycle.

Question 13

Which is usually the slowest way to regulate a reaction in a metabolic pathway?

A)Allosteric modulation.
B)Covalent modification.
C)Changing the enzyme concentration.
D)All of the above are usually equally as fast.

Question 14

Phosphorylation by protein kinases coordinates regulation of different pathways.Usually this phosphorylation ________ catabolic pathways and ________ anabolic pathways.

A)deactivates;deactivates
B)deactivates;activates
C)activates;deactivates
D)activates;activates

Question 15

Consider the synthesis of a biopolymer in which the addition of successive monomers occurs by the same kind of reaction(s).The synthesis of the polymer is a ________ pathway.

A)linear
B)cyclic
C)spiral
D)branched

Question 16

Which statement is false about most metabolic pathways?

A)Most pathways are reversible under physiological conditions.
B)Pathways serve to increase the efficiency of energy transfers.
C)The rates of pathway reactions vary to respond to changing conditions.
D)The enzymes that catalyze reactions in metabolic pathways generally catalyze only a single step.

Question 17

A distinct set of metabolic reactions is called a reaction ________.

A)network
B)cycle
C)pathway
D)mechanism

Question 18

For a step in a reaction pathway to serve as a control point it should be ________.

A)irreversible
B)endergonic
C)far from equilibrium
D)Both A and C
E)All of the above

Question 19

The citric acid cycle is

A)anabolic.
B)catabolic.
C)both A and B.
D)linear.

Question 20

The degradation of which class of biochemicals does not significantly contribute to the release of energy to cells?

A)Nucleic acids.
B)Proteins.
C)Lipids.
D)Carbohydrates.

Question 21

The reactions that digest foods in the mouth,stomach and intestine are classified as ________ reactions.

A)proteolytic cleavage
B)hydrolysis
C)free radical
D)reduction

Question 22

Which bond in ATP is primarily responsible for its being a high energy molecule?

A)A
B)B
C)C
D)D

Question 23

The hydrolysis of ATP to ADP has a △G°'of -30 kJ/mol.If in an E.coli cell the concentrations of ATP,ADP and inorganic phosphate are 7.90 mM,1.04 mM and 7.9 mM,respectively,which statement is true about the hydrolysis of ATP in the cell?(Assumeatemperature of 298 K.R = 8.315 J/K-mol)

A)Hydrolysis can proceed spontaneously.
B)The hydrolysis is at equilibrium.
C)The formation of ATP from ADP is occurring more rapidly than the hydrolysis.
D)The hydrolysis is being allosterically controlled.

Question 24

Compartmentation of enzymes

A)helps prevent loss by diffusion.
B)keeps separate pools of metabolites in cells.
C)can help control metabolic pathways.
D)All of the above.

Question 25

The most biochemically complex organisms are ________.

A)chemoheterotrophs
B)photoheterotrophs
C)heterotrophs
D)autotrophs

Question 26

The amount of energy recovered as ATP can be estimated by measuring free energy of hydrolysis of

A)phosphoester bond in ATP.
B)phosphoanhydride bonds in ADP.
C)phosphoester bond ADP.
D)phosphoanhydride bonds in ATP.
E)All of the above.

Question 27

Protein folding and lipid-bilayer formation result in decreased entropy for a protein molecule and bilayer components.The decrease in entropy is balanced by a large increase in the entropy of the surrounding ________.

A)salt solutions
B)temperature
C)pressure
D)water molecules

Question 28

Which is not generally a molecule used to conserve energy?

A)ATP
B)NADH
C)FAD
D)QH²

Question 29

Nucleoside triphosphates exist in a cell as complexes with

A)Phosphate ion.
B)Mg²+ only.
C)Mg³+ only.
D)Mg²+ and sometimes Mn²+.
E)All of the above.

Question 30

A reaction that best serves as a control point for regulation ________.

A)is a near equilibrium reaction
B)has a large positive △G
C)is metabolically irreversible
D)follows Michaelis-Menten kinetics

Question 31

Which are membrane-associated pathways?

A)Electron transport chain in eukaryotes.
B)Citric acid cycle in bacteria.
C)Photosynthesis.
D)Glycolysis.
E)Both A and C above.

Question 32

What defines a near-equilibrium reaction?

A)Q is close to Keq.
B)DE0' = 0.
C)The reaction is a closed system with no flux in or out of the system.
D)pH is approximately equal to pKeq.

Question 33

Anabolic and catabolic reactions in eukaryotes can occur simultaneously in cells.This is possible because ________.

A)they all occur in the cytosol
B)the anabolic and catabolic pathways do not share any intermediate metabolites
C)of the compartmentation of metabolites for the reactions of opposing pathways
D)all catabolic reactions are exergonic and all anabolic reactions are endergonic

Question 34

An organism that uses organic molecules as carbon sources and obtains energy by oxidizing inorganic molecules is a(n)________.

A)photoautotroph
B)chemoautotroph
C)photoheterotroph
D)chemoheterotroph

Question 35

A chemical reaction with a negative enthalpy change and a negative entropy change ________.

A)must be spontaneous
B)must be nonspontaneous
C)could be either spontaneous or nonspontaneous depending on the temperature
D)is not possible

Question 36

Calculate △G°'for the reaction shown if the mass action ratio,Q,is 5.3 × 102 M-1 and △G is 46 kJ/mol at a temperature of 298 K.(R = 8.315 J/K-mol)ADP + Pi ⇌ ATP

A)30 kJ/mol
B)-30 kJ/mol
C)61 kJ/mol
D)-61 kJ/mol

Question 37

The ultimate product of complete oxidation of carbohydrates is ________.

A)carbon dioxide
B)acetyl CoA
C)pyruvate
D)acetate ion

Question 38

Which thermodynamic quantity is used to determine if a reaction in a cell is spontaneous?

A)△G°'
B)△G
C)△H
D)△S

Question 39

Fatty acid synthesis occurs in the ________,while fatty acid breakdown occurs in the ________.

A)cytosol;mitochondria
B)cytosol;nucleus
C)mitochondria;cytosol
D)Golgi apparatus;cytosol

Question 40

The conversion of glucose-1-phosphate to glucose-6-phosphate by the enzyme phosphoglucomutase has a △G°' of -7.6 kJ/mol.Calculate the equilibrium constant for this reaction at 298 K and a pH of 7.(R = 8.315 J/K-mol)

A)0.003
B)0.047
C)1.00
D)21

Question 41

If the standard reduction potential of a certain half-reaction is -0.30 V,which statement below is true for this half-reaction to proceed as a reduction?

A)This half-reaction will proceed if it is coupled to another half-reaction that has a standard reduction potential greater than +0.30 V.
B)This half-reaction will proceed if it is coupled to another half-reaction that has a standard reduction potential greater than -0.30 V.
C)This half-reaction will proceed if it is coupled to another half-reaction that has a standard reduction potential less than -0.30 V.
D)It doesn't matter what half-reaction this is coupled with,it will proceed spontaneously.

Question 42

ATP is thermodynamically suited as a carrier of phosphoryl groups in animal cells because

A)it is stable under cell conditions.
B)it is not hydrolyzed in cells without enzyme action.
C)it is intermediate in group-transfer potential.
D)it can be produced from phosphocreatine.
E)All of the above.

Question 43

The formation of acetyl CoA is driven to completion by

A)the negative standard free energy for the first step of the reaction.
B)the negative standard free energy for the final step of the reaction.
C)removal of the product pyrophosphate by the enzyme pyrophosphatase.
D)the negative free energy for the formation of an ADP intermediate.
E)All of the above.

Question 44

ATP can be used to activate a substrate by

A)phosphorylation.
B)adding a nucleotidyl group.
C)producing inorganic phosphate.
D)Both A and B.

Question 45

What important high energy functional group is shown in molecule shown?

A)Methyl.
B)Ketone.
C)Thioester.
D)Thioanhydride.

Question 46

Levels of ATP and ADP are partly maintained in cells by

A)phosphoglucomutase.
B)the ADP concentration.
C)adenylate kinase.
D)and equilibrium with dissolved oxygen.

Question 47

Calculate the equilibrium constant for an oxidation-reduction reaction involving the transfer of 1 mole of electrons with ΔE0'= 0.25 V.(R = 8.315 JK-1mol-1,ℱ= 96.48 kJV-1mol-1,T = 298k)

A)1
B)6 × 10-⁵
C)1.7 × 10⁴
D)0.49

Question 48

The chemical energy generated by oxidation reactions cannot be captured by

A)NADH.
B)NADP+.
C)FMN.
D)FAD.
E)Q.

Question 49

Thioesters are similar to oxygen esters of carboxylic acids except that

A)the energy associated with their hydrolysis is much less than that of the phosphoanhydride in ATP.
B)they are more stable at neutral pH values in cells.
C)they are less stable because S is present instead of O in the linkage.
D)they are used in glycolysis and the citric acid cycle.
E)they are not hydrolyzed enzymatically.

Question 50

Phosphocreatine and phosphoarginine are ________ that are energy rich phosphate storage molecules found in animal ________ cells.

A)phosphagens;muscle
B)phosphagens;liver
C)plasminogens;muscle
D)plasminogens;liver

Question 51

The free energy for ATP hydrolysis in vivo is actually greater than the standard free energy change of -30 kJ mol-1 because

A)it has stronger electrostatic repulsion.
B)of the actual concentrations of ATP and its hydrolysis products in cells.
C)it can easily be formed from other nucleotide triphosphates.
D)it can participate in phosphoryl group transfers.
E)All of the above.

Question 52

Which compound has a greater free energy of hydrolysis than ATP?

A)Glucose 1-phosphate.
B)Any phosphoester.
C)Phosphoenolpyruvate.
D)Acetyl CoA.
E)All of the above.

Question 53

Which statement is false about ATP?

A)Its concentration in a particular cell usually fluctuates very little.
B)The concentration of ATP in cells is generally much lower than that of AMP.
C)Its concentration is maintained in part by adenylate kinase.
D)The intracellular concentration of ATP varies among cell types.

Question 54

In order for a reaction to proceed spontaneously from left to right as written,

A)ATP must be involved in the reaction.
B)a common intermediate must be formed.
C)the overall free-energy change must be negative.
D)a phosphate group must be transferred.
E)All of the above.

Question 55

What function group leads to ATP being an "energy-rich" compound?

A)Phosphate ester.
B)Carbonyl.
C)Ether.
D)Amido.

Question 56

ATP is classified as an energy-rich compound because

A)it complexes with Mg²+.
B)it has a relatively low free energy of hydrolysis.
C)its complete oxidation to carbon dioxide releases a large amount of energy.
D)of the free energy released from cleavage of the phosphoanhydride bond.

Question 57

g-Glutamyl phosphate is formed as an intermediate in the conversion of glutamate to glutamine by the enzyme glutamine synthetase because

A)it has a large negative free energy.
B)it is positively charged.
C)it is unstable in water.
D)it is a nucleophile.
E)All of the above.

Question 58

Which of the following is not a factor contributing to the large free energy of hydrolysis of ATP?

A)Electrostatic repulsion of oxygen atoms.
B)Better solvation of products than ATP itself.
C)Complexes with Mg²+ or Mn²+ ions.
D)Better stability of products than ATP itself.
E)Electrical shielding of products of hydrolysis.

Question 59

The synthesis of glutamine from glutamate and ammonia is an example of

A)transamination.
B)ATP phosphoryl group transfer.
C)ADP phosphoryl group transfer.
D)Inorganic phosphate group transfer.

Question 60

Enzymes that oxidize NADH can best be measured by the ________ .

A)increase in absorbance at 340 nm
B)decrease in absorbance at 340 nm
C)increase in absorbance at 250 nm
D)decrease in absorbance at 250 nm

Question 61

By linking a reaction that would not ordinarily proceed to the hydrolysis of ATP,the overall coupled reaction may be completed.

Question 62

Metabolic pathways generally have easily distinguished starting and stopping points.

Question 63

Studies of specific enzymes in cells may not give information about cell metabolism since

A)it is difficult to label many enzymes.
B)the pathways are too complex.
C)many enzymes are mutant ones.
D)conditions in isolation may not be like those inside the cell.
E)All of the above.

Question 64

Most of the fundamental metabolic pathways are present in all species.

Question 65

When a reduction half-reaction is ________ (negative,positive),electrons flow to the more readily reduced substance which is ________ (negative,positive)in value.

A)negative;negative
B)negative;positive
C)positive;positive
D)positive;negative

Question 66

Mutant organisms can be helpful in the study of metabolism because

A)one can compare the mutant to a non-mutant organism.
B)there may be an indication of a natural role for an enzyme.
C)there may be accumulations of products prior to defective enzymes.
D)the structures of enzymes may be deduced.
E)All of the above.

Question 67

Phosphatases catalyze the hydrolytic removal of phosphate groups.

Question 68

The biochemical reactions that degrade molecules,such as nutrients,are called anabolic reactions.

Question 69

The standard potential for electron transfer can be related to the standard free-energy change for redox reactions by using

A)a calorimeter.
B)an electrochemical cell.
C)two solutions separated by a salt bridge.
D)the Nernst equation.
E)the Faraday equation.

Question 70

Reactions of most metabolic pathways are in a state of equilibrium and have a △G equal to zero.

Question 71

The ability and capacity of coenzymes to become oxidized or reduced (reduction potential)may be found by

A)measuring the flow of zinc and copper electrons.
B)measuring the flow of electrons when compared to hydrogen gas at standard conditions.
C)measuring the number of H atoms present.
D)All of the above.

Question 72

The process of dissolving table salt,NaCl,in water involves an increase in entropy.

Question 73

ATP has the highest possible standard free energy of hydrolysis in cells;therefore it is the most energy-rich compound in living systems.

Question 74

Phosphorylation of enzymes involved in catabolic pathways usually activates them.

Question 75

All metabolic reactions occur in the cytosol of cells.

Question 76

The presence of Mg²+ ions decreases the free energy released by the hydrolysis of ATP.

Question 77

The phosphoester bond and phosphoanhydride bonds in ATP have the approximately same free energies of hydrolysis.

Question 78

In theory at least,the energy released by the oxidation of one molecule of NADH is sufficient to form ________ ATP molecule(s).

A)0.5 (meaning it takes about 2 NADH to form 1 ATP)
B)1
C)several
D)about 20
E)about 50

Question 79

A given cell type tends to maintain relatively constant internal concentrations of inorganic ions,enzymes and metabolites.

Question 80

Most metabolic reactions occur continuously at a fixed rate.