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Microbiology Unit 2 Exam > Geochemical Cycling > Flashcards

Geochemical Cycling Flashcards

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1
Q

All organisms eat at

A

C HOPKINS CaFe

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2
Q

What two elements do organisms expend the most energy trying to find?

A

Carbon and Nitrogen

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3
Q

How much of the atmosphere is made up of Carbon dioxide (CO2)

A

0.036% (convert to sugar during photosynthesis)

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4
Q

How much of the atmosphere is made up of Nitrogen (N2)

A

78% (have to make modifications to make it useable for organisms)

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5
Q

How much of the atmosphere is made up of Oxygen (O2)

A

21% (available to all organisms)

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6
Q

How much of the atmosphere is made up of Argon

A

0.9% (don’t really care about this one)

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7
Q

Biogeochemical cycling

A

Transitioning various chemicals between their organic an inorganic forms

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8
Q

Nitrogen fixation

A

Transitions N2 (gas) to NH4 (ammonia)

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9
Q

What bacteria does nitrogen fixation?

A

Diazotrophic (nitrogen-fixing) bacteria and archaea

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10
Q

Oxygenic phototrophs

A

Cyanobacteria

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11
Q

Anoxygenic phototrophs

A

Heliobacteria
Rhodospirillum
Chlorobium

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12
Q

What are some non-phototrophic nitrogen-fixing bacteria?

A

Symbiotic rhizobia in root nodules; mainly associated with legumes

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13
Q

Nitrification

A

NH4 (ammonia) to NO2- (nitrate) or NO3- (nitrite)

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14
Q

What carries out nitrification?

A

Autotrophic bacteria and archaea

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15
Q

Assimilation

A

NH4 (ammonia) to organic molecules

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16
Q

What carries out assimilation?

A

Plants, fungi, bacteria

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17
Q

Denitrification

A

NH4 (ammonia), NO2- (nitrate), NO3-(nitrite) to N2 (gas)

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18
Q

What carries out denitrification?

A

Wide range or, bacteria, archaea, and fungi

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19
Q

What is the nitrogen fixation reaction?

A

N2 + 8H+ + 8e- +16ATP –> 2NH3 + H2 + 16ADP + 16Pi

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20
Q

What enzymes carry out nitrogen fixation?

A

Nitrogen complex
Dihydrogen reductase and Dinitrogenase

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21
Q

What does dihydrogen reductase do?

A

Provides reducing power (e-)

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22
Q

What does dinitrogenase do?

A

Reduces the N2 (gas) in sequential steps

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23
Q

What are the steps to reducing N2 (gas)

A

N2 + H2 + 2e- –> HN=NH
HN=NH + 2H+ + 2e- –> H2N-NH2
H2N-NH2 + 2H+ + 2e- –> 2NH3

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24
Q

What is nitrogenase sensitive to?

A

Oxygen. requires a specialized environment (anaerobic)

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25
Q

Where are heterocysts (cyanobacteria) formed

A

Metabolically active cells under nitrogen-limiting conditions

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26
Q

What is degraded during development in heterocysts/cyanobacteria

A

Photosystem (no photosystem 2)

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27
Q

What is the purpose of heterocycts?

A

Dedicated to N2 fixation (eliminates reproductive potential)

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28
Q

What do metabolically adaptive cells (Azotbacter sp.) do?

A

Increase respiration rate (O2 enters but is used up rapidly)

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29
Q

What is the end product of nitrogen fixation?

A

Ammonia (NH3+)

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30
Q

what molecules can be incorporated directly into ammonia assimilation?

A

Ammonia in either form (NH3+ and NH4)

31
Q

What forms of nitrogen can be used for biosynthesis?

A

All other forms besides Ammonia must be converted into ammonia before they can be used

32
Q

What are the two pathways for Ammonia Assimilation?

A

GS-GOGAT pathway and GDH pathway

33
Q

What enzymes are involved in the GS-GOGAT pathway?

A

Glutamine synthetase
Glutamine: oxoglutarate aminotransferase

34
Q

What are the key points of the GS-GOGAT pathway?

A

ATP provides energy for the reaction
Able to work even when ammonia levels are low
NADPH provides reducing power (electrons)
Ammonia is added to an alfa-keto acid to create an amino acid

35
Q

What are the enzymes involved with the GDH pathway?

A

Glutamate dehydrogenase

36
Q

What are the key points of the GDH pathway?

A

No ATP required
Works well when cells are stressed for energy (low ATP concentrations)
ONly works when ammonia concentrations are high
NADPH provides reducing power (electrons)
Ammonia is added to an alfa-keto acid to create an amino acid

37
Q

Assimilation of Nitrate (NO3-) and Nitrite (NO2-) Pathway

A

Nitrate (NO3-) to Nitrite (NO2-) to NOH to NH2O2 to NH3 (ammonia)

38
Q

Nitrate reductase

A

Transfer of Nitrate (NO3-) to Nitrite (NO2-)

39
Q

Nitrite reductase

A

Nitrate (NO2-) to Nitrolic acid (NOH) to Hydroxylamine (NH2O2) to Ammonia (NH3)

40
Q

When did oxygen start to accumulate in the earth’s atmosphere?

A

After the first photosynthetic microbes appeared (3.5 billion ybp)

41
Q

How did the first photosynthetic microbes appear?

A

Oxygenic photosynthesis

42
Q

How are photons captured?

A

photopigments and their energy is transferred to electrons

43
Q

Where are the electrons that photons energy is transferred to coming from?

A

Water (hydrolysis)

44
Q

Charges electrons are passed from carrier to carrier in the ETC

A

Extracted energy used to pump protons across membrane to establish a gradient for ATP production

45
Q

Expanded e- is again charged by light and used to reduce NADP+

A

NADPH is then used in the carbon fixation reactions

46
Q

Complex organisms only arose once

A

O2 started to accumulate in the atmosphere

47
Q

What is a strong motive force for electron transfers?

A

Oxygen

48
Q

What is the most efficient pathway possible?

A

Aerobic respiration

49
Q

Carbon Fixation

A

CO2 (inorganic carbon) is reduced to CHO2 (organic) by autotrophs

50
Q

What happens to CHO2 (organic carbon)

A

Oxidized to CO2 gas by heterotrophs

51
Q

What cycles make up Carbon fixation?

A

Calvin cycle, Reductive TCA cycle

52
Q

What is the Calvin cycle used by?

A

Cyanobacteria and chloroplasts

53
Q

What enzyme is used in the Calvin cycle?

A

RuBisCo

54
Q

What is the primary substrate in the Calvin cycle?

A

Ribulose 1,5-bisphosphate

55
Q

What are in inputs of the Calvin cycle?

A

CO2, H2O, ATP, and NADPH

56
Q

What are the products of the Calvin cycle?

A

3-phosphoglycerate and ribulose 1,5-bisphosphate

57
Q

What is 3-phosphoglycerate used for?

A

Biosynthesis reactions

58
Q

What is the Reductive TCA Cycle used by?

A

Some autotrophic microbes other than cyanobacteria (both phototrophs and non-phototrophs)

59
Q

What is NADH used for the reverse TCA Cycle?

A

Reducing power

60
Q

What is ATP used for the reverse TCA Cycle?

A

Energy

61
Q

What is CO2 used for the reverse TCA Cycle?

A

Incorporated at the alfa-ketoglutarate and isocitrate formation steps

62
Q

What are intermediates used for the reverse TCA Cycle?

A

Can be siphoned off for biosynthetic reactions

63
Q

What is the most common inorganic form of sulfur in the environment?

A

Sulfate (SO4-)

64
Q

What are some characteristics of sulfate?

A

Highly oxidized, very stable, requires extensive reduction to H2S prior to assimilation

65
Q

In sulfur metabolism ATP provides

A

Activation energy

66
Q

In sulfur metabolism NADPH provides

A

Reducing power

67
Q

What can be directly incorporated into organic sulfur compounds?

A

H2S

68
Q

Phosphorus only exists in one natural form

A

PO4

69
Q

In phosphorus metabolism cycling simply involves

A

Interconversion between the organic nd inorganic forms

70
Q

In phosphorus metabolism, there is no

A

Gas phase

71
Q

Inorganic phosphate is naturally found in

A

Soil and rocks and dissolved in water

72
Q

Absorption

A

The incorporation of PO4 into organic molecules (nucleotides or phospholipids)

73
Q

Decomposition

A

Returning PO4 to inorganic form
Carried out by bacteria and fungi

Microbiology Unit 2 Exam (4 decks)

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