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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
Where are heterocysts (cyanobacteria) formed
Metabolically active cells under nitrogen-limiting conditions
26
What is degraded during development in heterocysts/cyanobacteria
Photosystem (no photosystem 2)
27
What is the purpose of heterocycts?
Dedicated to N2 fixation (eliminates reproductive potential)
28
What do metabolically adaptive cells (Azotbacter sp.) do?
Increase respiration rate (O2 enters but is used up rapidly)
29
What is the end product of nitrogen fixation?
Ammonia (NH3+)
30
what molecules can be incorporated directly into ammonia assimilation?
Ammonia in either form (NH3+ and NH4)
31
What forms of nitrogen can be used for biosynthesis?
All other forms besides Ammonia must be converted into ammonia before they can be used
32
What are the two pathways for Ammonia Assimilation?
GS-GOGAT pathway and GDH pathway
33
What enzymes are involved in the GS-GOGAT pathway?
Glutamine synthetase Glutamine: oxoglutarate aminotransferase
34
What are the key points of the GS-GOGAT pathway?
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
What are the enzymes involved with the GDH pathway?
Glutamate dehydrogenase
36
What are the key points of the GDH pathway?
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
Assimilation of Nitrate (NO3-) and Nitrite (NO2-) Pathway
Nitrate (NO3-) to Nitrite (NO2-) to NOH to NH2O2 to NH3 (ammonia)
38
Nitrate reductase
Transfer of Nitrate (NO3-) to Nitrite (NO2-)
39
Nitrite reductase
Nitrate (NO2-) to Nitrolic acid (NOH) to Hydroxylamine (NH2O2) to Ammonia (NH3)
40
When did oxygen start to accumulate in the earth's atmosphere?
After the first photosynthetic microbes appeared (3.5 billion ybp)
41
How did the first photosynthetic microbes appear?
Oxygenic photosynthesis
42
How are photons captured?
photopigments and their energy is transferred to electrons
43
Where are the electrons that photons energy is transferred to coming from?
Water (hydrolysis)
44
Charges electrons are passed from carrier to carrier in the ETC
Extracted energy used to pump protons across membrane to establish a gradient for ATP production
45
Expanded e- is again charged by light and used to reduce NADP+
NADPH is then used in the carbon fixation reactions
46
Complex organisms only arose once
O2 started to accumulate in the atmosphere
47
What is a strong motive force for electron transfers?
Oxygen
48
What is the most efficient pathway possible?
Aerobic respiration
49
Carbon Fixation
CO2 (inorganic carbon) is reduced to CHO2 (organic) by autotrophs
50
What happens to CHO2 (organic carbon)
Oxidized to CO2 gas by heterotrophs
51
What cycles make up Carbon fixation?
Calvin cycle, Reductive TCA cycle
52
What is the Calvin cycle used by?
Cyanobacteria and chloroplasts
53
What enzyme is used in the Calvin cycle?
RuBisCo
54
What is the primary substrate in the Calvin cycle?
Ribulose 1,5-bisphosphate
55
What are in inputs of the Calvin cycle?
CO2, H2O, ATP, and NADPH
56
What are the products of the Calvin cycle?
3-phosphoglycerate and ribulose 1,5-bisphosphate
57
What is 3-phosphoglycerate used for?
Biosynthesis reactions
58
What is the Reductive TCA Cycle used by?
Some autotrophic microbes other than cyanobacteria (both phototrophs and non-phototrophs)
59
What is NADH used for the reverse TCA Cycle?
Reducing power
60
What is ATP used for the reverse TCA Cycle?
Energy
61
What is CO2 used for the reverse TCA Cycle?
Incorporated at the alfa-ketoglutarate and isocitrate formation steps
62
What are intermediates used for the reverse TCA Cycle?
Can be siphoned off for biosynthetic reactions
63
What is the most common inorganic form of sulfur in the environment?
Sulfate (SO4-)
64
What are some characteristics of sulfate?
Highly oxidized, very stable, requires extensive reduction to H2S prior to assimilation
65
In sulfur metabolism ATP provides
Activation energy
66
In sulfur metabolism NADPH provides
Reducing power
67
What can be directly incorporated into organic sulfur compounds?
H2S
68
Phosphorus only exists in one natural form
PO4
69
In phosphorus metabolism cycling simply involves
Interconversion between the organic nd inorganic forms
70
In phosphorus metabolism, there is no
Gas phase
71
Inorganic phosphate is naturally found in
Soil and rocks and dissolved in water
72
Absorption
The incorporation of PO4 into organic molecules (nucleotides or phospholipids)
73
Decomposition
Returning PO4 to inorganic form Carried out by bacteria and fungi

Microbiology Unit 2 Exam (4 decks)

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