Deck 13: Phototrophy, Chemolithotrophy, and Major Biosyntheses

Question 1

Regarding CO2 fixation mechanisms in the autotrophic green sulfur bacteria,

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

Answer 1

B

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

Light energy is transferred from the antenna to the reaction center in purple phototrophic bacteria in packets called

A) excitons.
B) transferons.
C) superoperons.
D) humerons.

Answer 3

A

Question 4

Photosynthesis is most correctly defined as the

A) conversion of light energy to chemical energy.
B) conversion of carbohydrates into energy- yielding organic products.
C) absorption of light energy to produce carbohydrates.
D) production of carbohydrates by a plant or plantlike organism.

Question 5

Intracytoplasmic membrane systems housing vesicles known as chromatophores, which function in photosynthesis, are commonly found in

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

Question 6

Ferrous iron oxidation generally occurs in environments with

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

Question 7

"Special pair" is the name given to the in the photochemical complex of the purple bacteria.

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

Question 8

Plastocyanin is a

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

Question 9

What compound do most chemolithotrophs use as a source of carbon?

A) glucose
B) carbon dioxide
C) inorganic compounds
D) organic sources other than glucose

Question 10

During oxygenic photosynthesis,

A) oxygen is consumed.
B) oxygen functions as a catalyst.
C) oxygen is produced.
D) none of the above.

Question 11

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) energy flow.
C) reduction.
D) electron flow.

Question 12

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

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

Question 13

The absorption of by chlorophylls begins the process of .

A) ATP / autotrophy
B) light energy / photosynthetic energy conversion
C) ATP / photosynthetic energy conversion
D) light quanta / autotrophy

Question 14

Due to the sensitivity of dinitrogenase reductase, nitrogen fixation is inhibited by

A) ammonia.
B) oxygen.
C) hydrogen.
D) carbon dioxide.

Question 15

Which statement is TRUE?

A) The cytochromes contain iron atoms; chlorophyll contains a magnesium atom at the center of the porphyrin ring.
B) The cytochromes contain magnesium atoms; chlorophyll contains an iron atom at the center of the porphyrin ring.
C) Both the cytochromes and chlorophyll contain an iron atom but not a magnesium atom at the center of the porphyrin ring.
D) Both the cytochromes and chlorophyll contain magnesium atoms but not iron atoms at the center of the porphyrin ring.

Question 16

Oxygenic phototrophs use light to generate

A) ATP.
B) both ATP and NADPH.
C) NADPH.
D) organic carbon.

Question 17

Definitive proof of N2 fixation is obtained using

A) spectrophotometry to measure the opacity of possible nitrogen- containing substances.
B) gas chromatography to assay for nitrogen uptake.
C) electrophoresis to analyze the shifts in nitrogen content.
D) an isotope of nitrogen, 15N, as a tracer.

Question 18

The ammonia switch- off effect is a(n)

A) reversible reaction that converts ammonia to ammonium.
B) irreversible reaction performed by ammonia fixers.
C) mechanism where nitrogenase activity is shut down during excess ammonia and resumes when ammonia is limited.
D) rapid process used to conserve ATP consumption by ammoniase.

Question 19

Light harvesting protein complexes found in cyanobacteria and chloroplasts in red algae are called

A) phycobiliproteins.
B) rusticyanins.
C) cytochromes.
D) quinones.

Question 20

In which microorganisms are phycobilins present?

A) Archaea and Bacteria
B) cyanobacteria
C) algae
D) cyanobacteria and purple bacteria

Question 21

The master regulatory signal governing transcription of the photosynthetic gene cluster in anoxygenic phototrophs is

A) H₂.
B) N₂.
C) O₂.
D) CO₂.

Question 22

In synthesizing one hexose from carbon dioxide by the Calvin cycle, molecules of NADPH and _ molecules of ATP are required.

Question 23

The reduction of N2(g) for use as a source of nitrogen for biosynthetic needs is called nitrogen

A) fixation.
B) assimilation.
C) reduction.
D) oxidation.

Question 24

The Calvin cycle

A) requires both ribulose bisphosphate carboxylase and phosphoribulokinase.
B) is responsible for the fixation of CO2 into cell material.
C) utilizes both NAD(P)H and ATP.
D) does all of the above.

Question 25

The system that oxidizes reduced sulfur compounds directly to sulfate without the intermediate formation of sulfite is known as _.

Question 26

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

A) oxygen requirements.
B) energy source.
C) carbon source.
D) all of the above.

Question 27

Aerobic bacteria, which undergo nitrification, iron- , or sulfur- oxidation, all fix CO2 by using the cycle.

Question 28

Inorganic nitrogen compounds are oxidized aerobically by certain bacteria in the process known as .

Question 29

Anammoxosome lipids consist of fatty acids containing that are connected to glycerol by both ester and ether bonds.

Question 30

What is a quinine pool?

A) a complex of proteins tightly associated to quinines
B) a part of the photosynthetic membrane where electrons are held
C) a region in a cell's cytoplasm where cytochromes are highly abundant
D) All of the above are possible quinine pools.

Question 31

Carotenoids

A) function primarily as photoprotective agents.
B) are hydrophobic pigments that are present in photosynthetic membranes.
C) are involved in the capture of light energy.
D) do all of the above.

Question 32

Phycobiliproteins form into aggregates called that attach to the photosynthetic membranes. Cells with an increased number of these structures can grow at (higher/lower) light intensities.

Question 33

In most cases, the final product of sulfur oxidation is

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

Question 34

Photosynthesis in purple phototrophic bacteria begins when exciton energy strikes the
of bacteriochlorophyll a molecules.

Question 35

The rapid and simplistic method of assaying for nitrogenase activity uses

A) one of several techniques, all of which require oxygen to be absent in the assay.
B) the acetylene reduction assay that exploits the nonspecificity of nitrogenase.
C) mass spectrometry to observe 15N assimilation.
D) growth tests that add different nitrogen sources into media.

Question 36

A(n) is the low light efficiency structure that functions like an antenna and is found in the green sulfur and green nonsulfur bacteria.

Question 37

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

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

Question 38

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

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

Question 39

Organisms that obtain energy from the oxidation of an inorganic compound and require an organic compound as a carbon source are known as .

Question 40

Chlorophyll a is green because it absorbs

A) red and green light and transmits blue light.
B) green light and transmits red and blue light.
C) green light and transmits nothing.
D) red and blue light and transmits green light.

Question 41

Light- mediated ATP synthesis in phototrophic organisms involves electron transport through a sequence of electron carriers.

Question 42

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

Question 43

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

Question 44

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

Question 45

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

Question 46

Most iron- oxidizing bacteria are obligate acidophiles.

Question 47

Chemolithotrophic utilization of compounds requires the participation of several specific enzymes. The oxidation of hydrogen requires the enzyme , the oxidation of sulfur requires _ , participates in the oxidation of iron, and participates in the oxidation of nitrite. The oxidation of ammonia requires the participation of two enzymes, _ _ and .

Question 48

As long as Thiobacillus ferrooxidans has Fe3+ available, ATP synthesis can occur at the expense of the natural proton motive force that preexists across the cytoplasmic membrane.

Question 49

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 50

The pigments and all the components of the light- gathering apparatus are located within
systems.

Question 51

is the process by which CO2 is assimilated as a carbon source.

Question 52

Phototrophic purple bacteria such as Rhodobacter species grow only by photosynthesis, using bacteriochlorophylls to harvest light.

Question 53

Most phototrophic organisms are also autotrophs.

Question 54

Nitrogen fixation is repressed by and .

Question 55

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

Question 56

Some hydrogen bacteria have a soluble (cytoplasmic) as well as a membrane- integrated hydrogenase that each serves different functions.

Question 57

Photosynthetic membrane systems in chloroplasts are called .

Question 58

Light energy is used to oxidize CO2 to form organic compounds.

Question 59

The hydroxypropionate pathway may have been nature's first attempt at autotrophy in anoxygenic phototrophs.

Question 60

In photosynthesis, light energy is conserved as chemical energy.

Question 61

Illustrate the reaction center of a purple bacterium with the following features highlighted: antenna pigments, the special pair, protein H, protein L, protein M, and quinones. Also explain the importance of proximity for these components within a reaction center.

Question 62

In the autotrophic reactions of photosynthesis, chemical energy is used to reduce carbon dioxide.

Question 63

Phycoerythrin proteins absorb red light most strongly.

Question 64

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

Question 65

Photosystems I and II normally function in tandem in oxygenic photosynthesis.

Question 66

Why does an organism that is able to respire both aerobically and anaerobically preferentially undergo aerobic respiration?

Question 67

The FeS electron acceptor proteins of the green bacteria and the heliobacteria have a much more electronegative E0' than NADH.

Question 68

Explain why most iron- oxidizing bacteria are obligately acidophilic, and discuss some of the environments where these organisms are found.

Question 69

H2- oxidizing bacteria are all aerobic.

Question 70

Describe the anammox reaction.

Question 71

Chemotrophic denitrifying bacteria can couple the oxidation of Fe2+ to the reduction of NO3- to N2 under anoxic conditions.

Question 72

Explain why the discovery of iron- oxidizing phototrophs has important implications for both understanding the evolution of photosynthesis and explaining the large deposits of ferric iron (Fe3+) found in ancient sediments on Earth.

Question 73

Photosystem II absorbs shorter wavelengths of light, whereas photosystem I absorbs the longer wavelengths.

Question 74

Under what circumstances does oxygenic photophosphorylation use non- cyclic photophosphorylation and when does it use cyclic photophosphorylation? Also describe what occurs during each process.

Question 75

An organism that is mixotrophic can switch between being autotrophic and heterotrophic depending on its environment.

Question 76

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 77

Ammonia oxidized under aerobic conditions is a metabolism called anammox.

Question 78

Electron donors for chemolithotrophs may be geological, biological, or anthropogenic.

Question 79

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

Question 80

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