Deck 14: Metabolic Diversity of Microorganisms

Question 1

Two separate photosystems involved in electron flow is a hallmark of

A) anoxygenic phototrophs.
B) green sulfur bacteria.
C) oxygenic phototrophs.
D) purple bacteria.

Answer 1

C

Question 2

In photosynthesis, NADH and NADPH are produced from NAD ⁺ and NADP⁺ by

A) oxidation reactions.
B) reduction reactions.
C) both oxidation and reduction reactions.
D) neither oxidation nor reduction reactions.

Answer 2

B

Question 3

The metabolic diversity of photosynthetic bacteria stems from different

A) bacteriochlorophylls and pigments they contain.
B) chlorophylls they can have and organic compounds they can produce.
C) light-harvesting complexes, electron donors, and organic compounds they produce.
D) unrelated taxa capable of photosynthesis.

Answer 3

C

Question 4

The Calvin cycle

A) is responsible for the fixation of CO₂ into cell material.
B) utilizes both NAD(P)H and ATP.
C) requires both ribulose bisphosphate carboxylase and phosphoribulokinase.
D) uses CO₂, NAD(P)H, and ATP to make biomass with ribulose bisphosphate carboxylase and phosphoribulokinase.

Question 5

What will happen to a cyanobacterium that has its photosystem II (PSII) blocked?

A) Additional electron acceptors, such as NADP⁺, will be required to oxidize oxygen and overcome the lost PSII process.
B) Anoxygenic photosynthesis only using photosystem I (PSI) could occur by using cyclic photophosphorylation and an alternative electron donor such as H₂S.
C) It will die from being unable to obtain energy for photosynthesis.
D) Photons will generate excessive reactive oxygen species and the cyanobacterium will die as a consequence.

Question 6

Which group of microorganisms would the Calvin cycle LEAST likely be found in?

A) purple Bacteria
B) chemolithotrophic Bacteria
C) cyanobacteria
D) anoxygenic Chloroflexus

Question 7

Identifying carboxysomes in a bacterium suggests it

A) contains the reverse citric acid cycle.
B) has a deficient Calvin cycle and accumulated CO₂.
C) is in a carboxylic acid rich environment and is storing excess quantities for potentially harsh conditions.
D) will use the Calvin cycle to convert the concentrated into biomass.

Question 8

At some of the lowest light concentrations, ________ can still grow well due to their ________, which effectively harvest photons for energy.

A) green bacteria / antenna pigments
B) green bacteria / chlorosomes
C) purple bacteria / antenna pigments
D) purple bacteria / chlorosomes

Question 9

Membrane vesicles known as chromatophores, which function in photosynthesis, are commonly found in

A) algae.
B) green sulfur bacteria.
C) most autotrophic organisms.
D) purple phototrophic bacteria.

Question 10

Bacteriochlorophyll and chlorophyll contain ________ as a cofactor.

A) iron (II)
B) iron (III)
C) magnesium
D) manganese

Question 11

The path of electron flow in oxygenic phototrophs is referred to as the ________ scheme.

A) E
B) S
C) Q
D) Z

Question 12

ʺSpecial pairʺ is the name given to the ________ in the photochemical complex of the purple bacteria.

A) two bacteriochlorophyll a molecules
B) two bacteriochlorophyll b molecules
C) two quinones
D) two reaction centers

Question 13

Phycoerythrin is

A) the red phycobiliprotein.
B) the blue phycobiliprotein.
C) a type of carotenoid.
D) a green carotenoid.

Question 14

Plastocyanin is a

A) membrane-bound sac found in certain bacteria.
B) photosynthetic pigment found in some bacteria.
C) copper-containing protein in photosystem II that donates electrons to photosystem I.
D) blue-green bacterium known for its unusual photoreactive complex.

Question 15

Whether an organism is classified as a photoheterotroph or a photoautotroph depends on its

A) energy source.
B) carbon source.
C) oxygen requirements.
D) carbon and energy sources.

Question 16

Which of the following is NOT a role of carotenoids?

A) as accessory pigments
B) photoprotection
C) to produce singlet oxygen
D) to quench toxic oxygen species

Question 17

In most cases, the final product of sulfur oxidation is

A) hydrogen sulfide.
B) elemental sulfur.
C) sulfate.
D) thiosulfate.

Question 18

The process by which electrons from the quinone pool are forced against the thermodynamic gradient to reduce NAD⁺ to NADH is called reverse

A) proton motive force.
B) reduction.
C) electron transport.
D) energy flow.

Question 19

Regarding CO₂ fixation mechanisms in the autotrophic green sulfur bacteria,

A) Chlorobium uses the reverse citric acid cycle, and Chloroflexus uses the hydroxypropionate pathway.
B) Chlorobium uses the hydroxypropionate pathway, and Chloroflexus uses the reverse citric acid cycle.
C) both Chlorobium and Chloroflexus use the reverse citric acid cycle.
D) both Chlorobium and Chloroflexus use the hydroxypropionate pathway.

Question 20

Proteomic analysis of a microbial community indicated an abundance of phycobiliproteins. Which phototrophic group is likely active and abundant in this community?

A) cyanobacteria
B) eukaryotic phototrophs
C) green bacteria
D) prochlorophytes

Question 21

The only organisms that perform photosynthesis are ones that produce some form of

A) chlorophyll or bacteriochlorophyll.
B) carotenoids.
C) phycoerythrin.
D) phycocyanin.

Question 22

How is ATP made by an acetogen during CO₂ fixation?

A) Electrons from metal cofactors energize the electron transport chain and drive the proton motive force to activate ATP synthase.
B) Substrate-level phosphorylation of ADP occurs when coenzyme A is removed from acetyl-CoA.
C) It is made using substrate level phosphorylation and an ion motive force.
D) Acetyl CoA is produced from acetate and ATP is produced through substrate level phosphorylation.

Question 23

Ferrous iron (Fe²⁺) oxidation generally occurs in environments with

A) alkaline conditions.
B) high H⁺ concentrations.
C) high oxygen content.
D) little or no light present.

Question 24

Glucose fermentation by Clostridium spp. produces ATP only when acetate and butyrate are produced. Why do these organisms produce acetone and butanol after strong initial activity of generating ATP with acetate and butyrate byproducts?

A) Acetate and butyrate accumulation creates a deadly acidic environment, which acetone and butanol do not.
B) Acetate and butyrate are no longer needed for biosynthetic pathways.
C) Acetone and butanol serve as better sources for NAD(P)⁺ reduction.
D) Acetone and butanol production is favored for stability to store intracellular carbon sources for potential nutrient poor conditions.

Question 25

What metabolic advantage do cells have in storing the elemental sulfur byproduct from sulfide oxidation?

A) The cells avoid producing transport energy waste to secrete the sulfur.
B) The byproduct serves as an electron reserve for subsequent oxidation.
C) Sulfur decreases the intracellular acidification for non-acid-tolerant sulfide oxidizers.
D) The byproduct can be used for other biosynthetic pathways that use sulfur, such as Rieske Fe-S proteins.

Question 26

The foul-smelling putrescine byproduct suggests activity of

A) amino acid fermentation by clostridia.
B) secondary fermentation.
C) sulfur-oxidizing bacteria.
D) syntrophic carbohydrate metabolism.

Question 27

A researcher lacked the necessary equipment to measure methane production so instead monitored CO₂ concentration as an unknown archaeon grew and produced methane. Why might CO₂ NOT decrease while methane would still increase?

A) An alternative carbon source such as methanol was used.
B) CO₂ is not a carbon source used by methanogens.
C) CO₂ was used as an electron donor but not as a carbon substrate.
D) Methanogenic Archaea containing carboxysomes likely made measuring small losses of CO₂ difficult to conclude.

Question 28

Anammox is an anaerobic process that generates energy from ________ and forms N₂.

A) ammonia
B) ammonium
C) ammonia and nitrate
D) ammonia and nitrite

Question 29

Fermentation often produces CO₂, which can be used by ________ as an electron acceptor for energy.

A) acetogens
B) methanotrophs
C) methanogens
D) acetogens and methanogens

Question 30

Which of the following are NOT found within the photosynthetic gene cluster of Rhodobacter (a purple phototrophic bacterium)?

A) genes encoding reaction center and light-harvesting photocomplexes
B) genes encoding proteins involved in phycobiliprotein biosynthesis
C) genes encoding proteins involved in bacteriochlorophyll biosynthesis
D) genes encoding proteins involved in carotenoid biosynthesis

Question 31

Which metabolic strategy's existence suggests rapid growth is NOT always the best strategy to survive in the environment?

A) anaerobic fermentation
B) disproportionation
C) methylotrophy
D) syntrophy

Question 32

Which of the following reactions is classified as a heterofermentation?

A) hexose 2 lactate + 2 H⁺
B) HCOOH H₂ + CO₂
C) glucose lactate + ethanol + CO₂ + H⁺
D) fructose 3 acetate + 3 H⁺

Question 33

What would likely occur if an anammox bacterium was unable to use ladderane lipids?

A) Ammonium rather than ammonia would be used due to ammonia toxicity to other cellular processes within the anammoxosome.
B) It would require a different source for carbon assimilation.
C) Rates of anammox would be considerably slower due to a lack of localized metabolism.
D) Toxic products of the anammox reaction could kill the cell.

Question 34

A bacterium that catabolizes a compound by linking ion pumps to establish a proton or sodium motive force for energy

A) can circumvent substrate-level and oxidative phosphorylation.
B) makes insufficient energy to grow but enough for cellular maintenance to survive.
C) requires a second bacterium to cooperatively drive the gradient.
D) still requires another carbon substrate to provide a carbon source.

Question 35

A cell that lacks sulfite reductase but can still oxidize sulfur for energy could be identified by

A) adenosine phosphosulfate reductase coupled with substrate-level phosphorylation.
B) electrons being transferred to cytochrome c prior to shuttling them into the electron transport chain.
C) identifying an alternative quinone, flavoprotein, or cytochrome.
D) quantifying the release of sulfate byproduct.

Question 36

Methanogens that use methyl-CoM for biosynthesis use ________ as a substrate.

A) acetate
B) carbon monoxide
C) methane
D) methanol

Question 37

Obligate anaerobes can often use ________ electropositive redox couples than facultative anaerobes, and ________ metabolism is most common in this group as well.

A) lower / assimilative
B) lower / dissimilative
C) higher / assimilative
D) higher / dissimilative

Question 38

Alternative autotrophic routes to the Calvin cycle such as the reverse citric acid cycle and the hydroxypropionate pathway are unified in their requirement for

A) CO₂.
B) coenzyme A.
C) NAD(P)H.
D) organic compound(s) formed.

Question 39

The aerated upper layer of soil is likely to have ________ concentrations of H₂ for aerobic H₂-oxidizing Bacteria, so these bacteria likely ________.

A) high / thrive in such conditions by not competing with chemoorganotrophs
B) high / generate important reducing equivalents as byproducts for other microorganisms in the soil
C) low / do not occur in such habitats
D) low / will need a chemoorganotrophic way to grow as well

Question 40

In Bacteria, the most common oxidized form of nitrogen is ________ and of sulfur is ________.

A) nitrate / sulfate
B) nitrate / sulfite
C) nitrite / sulfate
D) nitrite / sulfite

Question 41

A bacterium that uses CO₂ as an electron source but CANNOT use it as a carbon source is considered a mixotroph.

Question 42

Phototrophic purple bacteria such as Rhodobacter species are capable of nitrogen fixation.

Question 43

The Calvin cycle provides autotrophs the ability to convert inorganic carbon into biomass and generate energy during this process.

Question 44

Organisms that aerobically catabolize methane use the intermediate ________ for biosynthesis and produce ________ when oxidizing the substrate for energy.

A) CH₂O (formaldehyde) / CO
B) CH₂O (formaldehyde) / CO₂
C) HCOO−(formate) / CO
D) HCOO−(formate) / CO₂

Question 45

Some purple bacteria harvest light using bacteriochlorophylls.

Question 46

Organisms grown with CO₂ as its sole carbon source must have energy in the form of ATP as well as reducing power.

Question 47

Chlorosomes are present in purple bacteria but absent in green sulfur and green nonsulfur bacteria.

Question 48

Carotenoids are hydrophobic accessory pigments and vary widely in the color they can absorb.

Question 49

The conversion of light into chemical energy is called photoautotrophy.

Question 50

Photosystem I is responsible for splitting a water molecule in the first step of oxygenic electron flow.

Question 51

Each chlorophyll and bacteriochlorophyll type is distinguished by its absorption spectrum.

Question 52

The serine pathway and ribulose monophosphate pathway can both be used by ________ as a way to incorporate carbon into biomass.

A) acetogens
B) anoxygenic hydrocarbon fermenters
C) methanogens
D) methylotrophs

Question 53

RubisCO converts ribulose bisphosphate and CO₂ into two molecules of 3-phosphoglyceric acid (PGA).

Question 54

Which of the following is the best potential reason that anoxic methane-oxidizing Archaea have not also acquired the ability to reduce sulfate?

A) Sulfate is toxic to these archaeans.
B) Having fewer metabolic capabilities decreases the archaeonʹs genome size and gives it flexibility to interact with other reducing bacteria, such as nitrate bacteria.
C) The archaeans are too rare to survive without the bacteria.
D) The methane-oxidizing Archaea are not capable of acquiring this metabolic capability.

Question 55

Chemolithotrophs that obtain electrons from donors such as sulfide use the same electron transport chains to obtain energy as chemoorganotrophs.

Question 56

Reaction centers ONLY indirectly receive photon energy via light-harvesting molecules.

Question 57

What metabolism would be favored when there is a lack of electron acceptors?

A) fermentation
B) anoxygenic photosynthesis
C) anoxic ammonia oxidation
D) acetogenesis

Question 58

Despite being called the reverse citric acid cycle, this pathway is currently identified as the most ancient and widespread autotrophic pathway.

Question 59

What products would be expected to form during anoxic degradation of the seven-carbon compound benzoate following reduction and cleavage of the aromatic ring?

A) 1 three-carbon compound and 1 four-carbon compound
B) 1 three-carbon compound and 2 two-carbon compounds
C) 2 three-carbon compounds and CO₂
D) 3 two-carbon compounds and CO₂

Question 60

Photooxidation reactions can lead to the production of toxic forms of oxygen and the destruction of the photosynthetic apparatus.

Question 61

Because H₂ levels in oxic environments are transient, it is likely that aerobic hydrogen bacteria shift between chemoorganotrophy and chemolithotrophy depending on levels of organic compounds and hydrogen in their habitats.

Question 62

Iron-oxidizing bacteria grow better in alkaline environments where protons are less likely to abiotically convert Fe²⁺ into Fe³⁺.

Question 63

Bacteria that are capable of oxidizing both iron and sulfur usually have a strong preference for sulfur oxidation because it yields more energy.

Question 64

One result of the oxidation of reduced sulfur compounds is a rise in the pH of the medium.

Question 65

Some anaerobic bacteria not only use organic compounds as a carbon source but can also use them for energy as well.

Question 66

A monooxygenase can always be distinguished from a dioxygenase by incorporating only one oxygen atom from O₂ into the substrate rather than both.

Question 67

Beta-oxidation exclusively removes two carbons at a time to catabolize fatty acids regardless of the carbon chain length.

Question 68

Some sulfur-oxidizing bacteria can simultaneously reduce nitrate, which enables them to grow anaerobically.

Question 69

Fermentation of organic compounds can produce acetate.

Question 70

Reductive dechlorination involves chlorinated organic compounds serving as electron donors and releasing the chloride in inorganic forms.

Question 71

In what types of organisms are carboxysomes found and what advantage do they provide for a cell?

Question 72

The acetyl-CoA pathway is a primary route for carbon source utilization.

Question 73

Heterofermentation CANNOT be differentiated from homofermentation based on the compound fermented.

Question 74

Compare and contrast the prokaryotic and eukaryotic light-gathering machinery function and spatial organization. Why do various chlorophylls show different absorption spectra?

Question 75

Bacteria that degrade aromatic compounds with reductions steps rather than oxygenase activity prior to ring fission are likely to be anaerobes.

Question 76

Describe what occurs when elemental sulfur is provided externally as an electron donor and how energy is obtained.

Question 77

Due to a chemical equilibrium, a syntrophic relationship can be disrupted if the product from the first partnerʹs metabolism is removed too quickly.

Question 78

What is the difference between chlorophyll and bacteriochlorophyll, and which organisms contain each?

Question 79

When elemental sulfur is provided externally as an electron donor, the organism must attach itself to the sulfur particle because of the extreme insolubility of elemental sulfur.

Question 80

Explain the Calvin cycle process that produces a full molecule of glucose and regenerates the ribulose bisphosphate molecule.