Carbon Cycle

Question 1

List the major carbon reservoirs

Answer 1

• rock sediments
• humus
• land plants

Question 2

Define commensalism

Answer 2

• one population benefits and the other is unaffected (co-metabolism)

Question 3

Define co-metabolism

Answer 3

• one organism does gratuitous transformation

Question 4

Define gratuitous transformation

Answer 4

free transformation

Question 5

Define synergism

Answer 5

• both populations benefit (+/+)

Question 6

What are the 2 elements needed for carbon cycling?

Answer 6

• oxygen
• hydrogen

Question 7

What is humus?

Answer 7

mixture of organic materials from dead organic matter

Question 8

Example of humus

Answer 8

soil microorganisms resistant to decomposition

Question 9

What is the importance of land plants?

Answer 9

• contain large amount of ORGANIC CARBON and are major site of CO2 fixation
• relied on to pull CO2 back

Question 10

What is carbon essentially cycled between?

Answer 10

inorganic CO2 (in atmosphere and dissolved in water) and organic compounds

Question 11

What is the importance of phytoplankton

Answer 11

-MAJOR fixation of CO2 and generation of O2

Question 12

What are methanotrophs and where are they found?

Answer 12

• utilize CH4 compounds
• found at interface = zone of transition of anoxic to oxic

Question 13

What is the major contributor of CO2

Answer 13

• decomposition of dead organic material

Question 14

How is carbon cycle tightly linked to O2 cycle?

Answer 14

• CO2 fixated (incorporated into organic compounds) by oxygen generating phototrophs that release O2
• released O2 is used for aerobic respiration for oxidation of organic matter back into CO2

Question 15

What are phototrophs?

Answer 15

• use light as energy
• aerobic or anaerobic (purple and green sulfur bacteria)

Question 16

Give an example of a phototroph

Answer 16

• cyanobacteria
• algae

Question 17

What is oxygenic photosynthesis? give an example of what carries it out

Answer 17

• carried out by aquatic “higher” plants
• ex. microalgae, cyanobacteria

Question 18

What is a heterocyst?

Answer 18

dense structure to transform
**enzyme responsible is extremely sensitive to oxygen

Question 19

Define chemosynthesis and give an example

Answer 19

• new organic carbon from CO2 and water
• often use light as energy source
• ex. chemolithotrophs

Question 20

What is respiration and where does it occur?

Answer 20

• organic carbon used and resynthesized = released to atmosphere
• occurs in light or dark by PHOTOTROPHIC ORGANISMS

Question 21

What is the result of organic matter decomposition (2 THINGS)

Answer 21

• methane (via methanogens)
• CO2 via chemoorganotrophs

Question 22

What is critical for organic matter decomposition?

Answer 22

a balance between oxidative and reductive portions of carbon cycle

Question 23

What is critical in the respiration process?

Answer 23

• net positive balance of photosynthetic rate over respiration

Question 24

Define chemoorganotroph

Answer 24

• attack carbon as organic source

Question 25

Define methanogenesis

Answer 25

• formation of methane
• reduces CO2 to methane via methyl reductase
• ABSENCE OF OXYGEN

Question 26

Define methanogens

Answer 26

• a specialized group of obligate anaerobic archaebacteria
• narrow substrate range and need to cooperate with other organisms (syntrophs)

Question 27

What are methanogens critical for?

Answer 27

carbon transformation
- consume H2

Question 28

What is the prefered habitat for methanogens

Answer 28

• syntrophic
• NO OXYGEN
  —> swamps and marshes, often bottom of lakes
• anoxic production of C cycle is carried out by cooperative organisms

Question 29

In habitats with methanogens, how is the anoxic portion of the carbon cycle carried out?

Answer 29

• by cooperation of different groups of bacteria
• ex. degradation of organic matter under anaerobic conditions

Question 30

What would happen if there was no Carbon transformation in habitats with methanogens?

Answer 30

lots of excess CO2

Question 31

What is the state of soil that is waterlogged

Answer 31

anoxic - limited free O2

Question 32

What is cellulolytic bacteria?

Answer 32

high molecular weight polymer

Question 33

What is a primary fermenter? give an example

Answer 33

• breaks down simpler forms/compounds
• ex. glucose–>acetate and CO2

Question 34

What is a secondary fermenter? give an example

Answer 34

• Specifically attack compounds once primary is broken down
• ex. H2 producers

Question 35

What consumes H2 produced by primary fermenters? what does this do?

Answer 35

• methanogens
• mediates pH (avoids toxicity)

Question 36

Are lignin and aliphatic saturated hydrocarbons degraded anaerobically?

Answer 36

No - stay intact because it requires O2 for breakdown

Question 37

Define methanotroph

Answer 37

• subset of methylotrophs that oxidizes methane
  ** NOT METHANOGENS

Question 38

Define methylotrophs, give an example

Answer 38

• 1-C compound for energy and carbon, grow because they feed on carbon
• ex. used in animal feed

Question 39

What is the greenhouse effect? Give an example.

Answer 39

• gasses trap infrared heat from earth –> disrupts climate patterns
• ex. excess CO2 due to deforested land that could “fix” it

Question 40

What are some common C1 compounds that support prokaryote growth?

Answer 40

• CO3
• CH4
• methanol
• Methylamine

Question 41

What does pathway of CO2 assimilation =?

Answer 41

autotrophic CO2 fixation

Question 42

How is autotrophic CO2 fixation carried out?

Answer 42

• Calvin cycle (aerobes)
• acetyl=CoA pathway (anaerobes)