Deck 14: Catabolism of Organic Compounds

Question 1

The key enzyme of the acetyl- CoA pathway is

A) carbon dioxide dehydrogenase.
B) homacetogen dehydrogenase.
C) acetyl dehydrogenase.
D) carbon monoxide dehydrogenase.

Answer 1

D

Question 2

Most acetogens that produce and excrete acetate are

A) gram- negative Bacteria.
B) protists.
C) Archaea.
D) gram- positive Bacteria.

Answer 2

D

Question 3

Which of the following is NOT a characteristic of syntrophy?

A) Most are secondary fermentations.
B) The free energy change for the second reaction is positive.
C) The net ATP yields are often low.
D) It requires several different organisms.

Answer 3

D

Question 4

Beta oxidation involves the

A) synthesis of a series of two- carbon compounds.
B) splitting of hexoses into two- carbon units.
C) production of disaccharides.
D) cleaving of two- carbon units from fatty acid chains.

Question 5

An example of syntrophy is

A) H2 production by one organism linked to H2 consumption by a different organism.
B) O2 evolution.
C) establishment of the proton motive force.
D) ATP production.

Question 6

What two condition(s) must exist before the enzymes involved in nitrate (NO3- ) reduction are fully expressed?

A) Both nitrate and oxygen must be absent.
B) Nitrate must be absent, and oxygen must be present.
C) Nitrate must be present, and oxygen must be absent.
D) Both nitrate and oxygen must be present.

Question 7

The Entner- Doudoroff pathway is a variant of traditional glycolysis, where

A) both ATP and NADPH yields are double relative to glycolysis.
B) ATP yield is double and NADPH yield is half relative to glycolysis.
C) both ATP and NADPH yields are half of glycolysis.
D) ATP yield is half and NADPH yield is double relative to glycolysis.

Question 8

When facultative anaerobes are exposed to oxygen, they

A) modify their gene expression to favor aerobic metabolism and downregulate anaerobic metabolism genes.
B) undergo both aerobic and anaerobic pathways simultaneously to maximize energy yields.
C) primarily manipulate enzyme activities through biochemical reactions.
D) perform both A and B.

Question 9

The first step of dissimilative nitrate reduction involves

A) nitrite reductase.
B) nitrite oxidase.
C) nitrate reductase.
D) nitrate oxidase.

Question 10

Methanogenesis is an example of

A) photophosphorylation.
B) substrate- level phosphorylation.
C) anaerobic respiration.
D) aerobic respiration.

Question 11

What product is energy conserving during anaerobic fermentation because it allows the organism to make ATP by substrate- level phosphorylation?

A) pyruvate
B) acetate
C) hydrogen
D) glucose

Question 12

The production of H2 during fermentation is associated with the activity of an iron- sulfur protein called

A) rusticyanin.
B) hydrogenase.
C) hydroxylamine oxidoreductase.
D) ferredoxin.

Question 13

Which product(s) is/are formed from the disproportionation of thiosulfate?

A) an oxidized sulfate and a reduced hydrogen sulfide
B) two sulfonates
C) two thiolate ions
D) an oxidized thiolate and a reduced sulfonate

Question 14

What group of microorganisms carries out methanogenesis?

A) facultatively aerobic gram- negative Bacteria
B) a group of strictly anaerobic Archaea
C) gram- positive Bacteria
D) a group of strictly anaerobic gram- negative Bacteria

Question 15

In terms of oxygen requirements, homoacetogens and methanogens are

A) strict anaerobes.
B) facultative anaerobes.
C) facultative aerobes.
D) strict aerobes.

Question 16

All acetogens reduce CO2 to acetate by the

A) hydroxypropionate pathway.
B) acetyl- CoA pathway.
C) Calvin cycle.
D) reverse citric acid cycle.

Question 17

The coenzymes F420 and 7- mercaptoheptanoylthreonine phosphate (CoB) are electron in .

A) donors / acetogenesis
B) acceptors / acetogenesis
C) donors / methanogenesis
D) acceptors / methanogenesis

Question 18

Energy conservation in acetogenesis uses

A) photophosphorylation.
B) oxidative phosphorylation.
C) both substrate- level and oxidative phosphorylations.
D) substrate- level phosphorylation.

Question 19

The most oxidized form of sulfur is

A) dihydrogen sulfide.
B) sulfur hydride.
C) sulfate.
D) sulfite.

Question 20

Most denitrifying prokaryotes are

A) aerobes.
B) facultative aerobes.
C) microaerophiles.
D) obligate anaerobes.

Question 21

In a number of fermentations, electron balance is maintained by the production of
.

Question 22

Anoxic degradation of aliphatic and aromatic hydrocarbons use oxygen in the form of
rather than molecular oxygen (gas) to begin catabolism.

Question 23

Redox balance is achieved in fermentation by the production of

A) molecular hydrogen.
B) electrons.
C) molecular oxygen.
D) acids.

Question 24

Some of the most common electron acceptors in anaerobic respiration is/are

A) inorganic acids.
B) inorganic nitrogen compounds.
C) carbon dioxide.
D) inorganic sulfur compounds.

Question 25

While some aerobic bacteria are capable of growth on acetate as a sole carbon source, many anaerobic bacteria produce acetate during _.

Question 26

is the process involving the addition of an inorganic phosphate, which results in the formation of a hexose phosphate rather than free hexose.

Question 27

The biological production of methane is known as .

Question 28

In the , one amino acid functions as the electron donor and is oxidized, whereas another amino acid is the electron acceptor and is reduced.

Question 29

Sulfate is chemically quite stable and cannot be reduced without first being activated to
.

Question 30

Electrons for the reduction of CO2 to CH4 come mainly from

A) glucose.
B) H2.
C) CO2.
D) ferric iron.

Question 31

When adequate supplies of electron acceptors are not available in anoxic microbial environments, organic compounds will be catabolized by .

Question 32

The primary means by which gaseous nitrogen is formed biologically is .

Question 33

is the situation in which two different organisms can together degrade some substances that neither could degrade separately.

Question 34

Many pseudomonads use _ for catabolism of sugars.

Question 35

Energy conservation in methanogenesis is linked to the .

Question 36

The direct synthesis of NADPH uses the pathway.

Question 37

Complete oxidation of fatty acids yields

A) NAD+ or NADP+.
B) acetyl- CoA.
C) electron pairs.
D) CH_4.

Question 38

Which of the following is NOT true about cellulase enzymes? They

A) produce more water- soluble products, such as glucose, than cellulose.
B) can produce disaccharides such as cellobiose.
C) can be active in anoxic environments.
D) are rare in Bacteria but relatively abundant in Archaea.

Question 39

Acetyl- CoA is an energy- rich compound because after it is converted to acetylphosphate
can be synthesized.

Question 40

When an inorganic compound is reduced for use in biosynthesis, the reduction process is called , whereas the reduction of the compound as an electron acceptor for energy metabolism in anaerobic respiration is called .

Question 41

TMAO and DMSO are both organic electron that are found in environments.

Question 42

Oxygenases are enzymes that catalyze incorporation of oxygen atoms from O2 into organic compounds.

Question 43

Only a restricted variety of primarily prokaryotic organisms carry out dissimilative metabolism.

Question 44

A minimal requirement for an energy- conserving reaction is that it must yield sufficient free energy to .

Question 45

When growing autotrophically with molecular hydrogen, sulfate- reducing bacteria use the
as a means of incorporating CO₂ into cell material.

Question 46

A key enzyme of the acetyl- CoA pathway is .

Question 47

Catabolism of two- and three- carbon molecules such as pyruvate use CO2 and ATP to form a four- carbon oxalacetate, a key compound required in the cycle that generates energy.

Question 48

The differences observed in the fermentation patterns of homofermentative and heterofermentative lactic acid bacteria are due to the presence or absence of the enzyme lactase.

Question 49

Five- carbon sugars, called _ , must be synthesized if not bioavailable because they form the backbone of .

Question 50

Two general mechanisms for the catabolism of organic compounds are _ and
.

Question 51

Oxygen's only role in metabolic processes is to serve as an electron acceptor in energy- generating reactions.

Question 52

The concentrations of reactants and products in a reaction do not affect the energetics of the reaction.

Question 53

Enzymes that catalyze incorporation of both oxygen atoms from O2 into organic compounds are called , and enzymes that incorporate one of the two oxygen atoms from O2 into organic compounds are called .

Question 54

Fatty acids can serve as electron donors, because they are already reduced.

Question 55

The two types of methanogenic coenzymes are and .

Question 56

In fermentation, ATP is typically synthesized by substrate- level phosphorylation.

Question 57

is a process in which some molecules of a substrate are oxidized while some are reduced.

Question 58

Microbes that can dissimilate sulfur can also assimilate it, but not all that assimilate sulfur can fully dissimilate it.

Question 59

Chlorinated compounds can function as electron acceptors for anaerobic respiration in the process known as oxidative dechlorination.

Question 60

Long hydrocarbon chains (> C20) are more readily catabolized than are shorter hydrocarbon chains.

Question 61

The oxidation- reduction balance referred to when discussing redox reactions is theoretical rather than real because the numbers of protons and electrons do not necessarily match.

Question 62

N2O can be abiotically converted to NO by sunlight.

Question 63

When growing autotrophically from H2, sulfate reducers use the acetyl- CoA pathway that incorporates CO2 into the cell.

Question 64

When lactate or pyruvate is the electron donor during dissimilative sulfate reduction, ATP is produced from the proton motive force and additional ATP is produced during the oxidation of pyruvate.

Question 65

Certain bacteria are able to obtain energy by fermentation of amino acids.

Question 66

Explain how arsenic contamination of well water in Bangladesh is related to anaerobic respiration by bacteria, and distinguish arsenate from arsenite.

Question 67

Despite being unable to conserve energy from the main reactions in glycolysis, Pyrococcus furiosus
actually synthesizes more ATP from glucose than many other glucose fermenters.

Question 68

The fermentation of certain compounds yields insufficient energy to synthesize ATP by substrate- level phosphorylation, yet energy conservation leading to ATP synthesis still occurs.

Question 69

Hydrogenase plays a role in sulfate reduction only if the organism is growing on an organic compound.

Question 70

Describe conditions in which the glyoxylate cycle is used and the processes involved in the cycle.

Question 71

Mixed acid fermenters are capable of using several different acids as substrate to yield one fermentation product.

Question 72

A number of bacteria and several molds and yeasts can use hydrocarbons as electron donors to support growth under aerobic conditions.

Question 73

Most syntrophic reactions are primary fermentations.

Question 74

Inorganic arsenic compounds can serve as electron acceptors for anaerobic respiration.

Question 75

Nitrate and sulfate reduction can be either assimilative or dissimilative.

Question 76

Explain how denitrification contributes to the formation of acid rain.

Question 77

The energy released from the oxidation of an electron donor using molecular oxygen as an electron acceptor is less than if the same compound is oxidized with an alternate electron acceptor.

Question 78

Using nitrogen as an example, explain the differences between assimilative and dissimilative metabolism.

Question 79

Compare and contrast the sodium motive force and the proton motive force in methanogens.

Question 80

Bacteria such as Dehalococcoides, which reductively dechloronate toxic compounds such as polychlorinated biphenyls (PCBs), are attractive for bioremediation efforts.