Lecture 16 - Carbon Cycling

Question 1

What are the 4 nutrient cycles microorganisms use?

Answer 1

carbon, iron, nitrogen, sulfur (CINS)

Question 2

Which nutrient cycle is the most important for microbes?

Answer 2

nitrogen

Question 3

What are the 3 man-made things that contribute to the carbon in the atmosphere and results in the increase of atmospheric CO2?

Answer 3

fossil fuels, deforestation, cement production

Question 4

What is carbonated rock? What is a rule with this carbon source?

Answer 4

oceanic earth’s crust/fossil fuel source, should be inactive | should NOT be cycled, but it us used anyways

Question 5

Which is the largest carbon reservoir in the planet?

Answer 5

carbonated rock

Question 6

Which is the smallest carbon reservoir in the planet?

Answer 6

atmospheric CO2

Question 7

Which carbon reservoir is the most actively cycled?

Answer 7

atmospheric CO2

Question 8

What is due to the drastic increase in atmospheric CO2?

Answer 8

past 100 years = industrialization

Question 9

What are the 2 carbon reservoirs in the ocean?

Answer 9

carbonate rock and dissolved/particulate organic material (DOM/POM)

Question 10

What are the 4 carbon reservoirs on land?

Answer 10

land plants (biota), humus, fossil fuels and earth’s crust

Question 11

How do carbon reservoirs relate to the issue of global warming?

Answer 11

CO2 and CH4 = high levels in sky = traps heat and doesn’t let it escape

Question 12

Microorganisms may play a role in more than one nutrient cycle (ex: can fix both nitrogen and carbon). How does this overlap affect the microbe community?

Answer 12

can drive how these organisms are structured within the community

Question 13

By how much (%) has atmospheric CO2 increased in the past century?

Answer 13

28%

Question 14

What are autotrophs?

Answer 14

takes up CO2&raquo_space;> carbon fixation

Question 15

What are heterotrophs?

Answer 15

takes organic carbon &raquo_space;> carbon respiration &raquo_space;> produce CO2

Question 16

What is the primary productivity of our planet a result of? (50% what and 50% what?)

Answer 16

50-plants | 50: cyano-b, algae, microbes (CAM)

Question 17

What cycle uses carbon anaerobically?

Answer 17

methane cycle

Question 18

What are the 4 predominant forms of organic carbon in the environment?

Answer 18

peptidoglycan, chitin, plant polymers, insect exoskeleton

Question 19

Why are organic polymers important?

Answer 19

help support heterotrophic activity

Question 20

What are the 3 different components that make up a plant? (order them from which makes up most of the plant to least)

Answer 20

cellulose, hemicellulose, lignin

Question 21

Where does the environment get peptidoglycan from?

Answer 21

bacterial cell wall

Question 22

Where does the environment get chitin from?

Answer 22

fungal cell wall

Question 23

What is cellulose?

Answer 23

homogenous molecule - glucose subunit repeats connected via beta-1,4-glycosidic linkage

Question 24

How is cellulose a problem for microbes?

Answer 24

large molecule and insoluble in water

Question 25

How do microbes get a large insoluble molecule across their cell walls?

Answer 25

secretes enzymes to break it down into smaller pieces

Question 26

What is cellulase?

Answer 26

NOT one enzyme, CLASS of enzymes that break down cellulose

Question 27

What are the 3 major enzymes that play a role in the breakdown of cellulose?

Answer 27

B1,4-endoglucanase, B1,4-exoglucanase, cellobiase (B1,4-glucosidase)

Question 28

What is beta1,4-endoglucanase?

Answer 28

randomly breaks up cellulose into shorter pieces by targeting glycosidic (beta 1,4) linkage

Question 29

What is beta1,4-exoglucanase?

Answer 29

more specific = goes at end of cellulose and breaks bond at every 2 subunits == produces di-glucose

Question 30

What is beta1,4-glucosidase?

Answer 30

not all cells secrete this, cuts cellobiose into single glucose subunits

Question 31

What is cellobiose?

Answer 31

di-glucose that can be transported into cell

Question 32

What is the aerobic pathway glucose is used when it gets inside the cell?

Answer 32

TCA >>> respiration >>> made CO2

Question 33

What is the anaerobic pathway glucose is used when it gets inside the cell?

Answer 33

fermentation >>> made acetate and alcohol >>> use for energy

Question 34

What is hemicellulose? What is another name for it?

Answer 34

(xylan) heterogeneous and diverse molecule, different sugar forms, branching occurs | common in plants

Question 35

Why does it take longer and is it more difficult for organisms to break down hemicellulose?

Answer 35

branching and how super diverse it is = need a lot of enzymes because of how many different sugars there are

Question 36

What is starch?

Answer 36

glucose repeats with branching

Question 37

What are the enzymes involved in the break down of starch?

Answer 37

alpha amylase and glucoamylase

Question 38

What is a hemicellulose polymer?

Answer 38

pectin

Question 39

What does alpha amylase do?

Answer 39

attacks starch at non-reducing end = makes maltose

Question 40

What does glucoamylase do?

Answer 40

breaks alpha (1,4) and (1,6) glycosidic bonds

Question 41

What are the differences and or similarities in the structures of chitin and peptidoglycan?

Answer 41

chitin = only NAG subunits | peptidoglycan = NAG and NAM

Question 42

What molecules does N-acylglucosamine (NAG) contain?

Answer 42

carbon and nitrogen

Question 43

Why are chitin and peptidoglycan important and unique than the other organic polymers?

Answer 43

NAG serves as a source for both nitrogen cycle and or carbon cycle

Question 44

What is lignin?

Answer 44

complex and heterogeneous molecule | helps support plant's structure/stability, protects from pathogens, encases hemicellulose

Question 45

What are the basic building blocks of lignin?

Answer 45

2 aromatic amino acids: tyrosine and phenylalanine

Question 46

What is phenylpropene?

Answer 46

what the lignin building blocks are converted into that randomly polymerize until structure is complete

Question 47

What makes lignin difficult and slow for microbes to break down?

Answer 47

complexity, diversity of molecule and aromatic rings within structure

Question 48

What is lignin peroxidase?

Answer 48

(*nonspecific extracellular*) peroxidase that breaks down lignin by: O2-based free radicals that react with lignin and releases the subunits | needs to be in aerobic environment

Question 49

Briefly describe how lignin is broken down in order to enter the TCA cycle. What is the end product from the TCA cycle due to lignin?

Answer 49

lignin broken down to smaller subunits = further broken down >>> TCA >>> made CO2 and water

Question 50

What do all enzymes used to break down the 4 organic polymers have in common?

Answer 50

all enzymes are secreted by the cell

Question 51

What is the number one most common greenhouse gas?

Answer 51

CO2

Question 52

What is the second most common greenhouse gas?

Answer 52

methane

Question 53

What is methane?

Answer 53

carbon compound5% that is 22x more effective in trapping heat

Question 54

What percent concentration of methane is it considered flammable and an explosive gas?

Answer 54

5%

Question 55

Where is a lot of methane produced and why?

Answer 55

landfills : stuff decomposes = methane released

Question 56

What percent concentration of methane can be tracked, converted, collected, and used for generating electricity?

Answer 56

35%

Question 57

What is a more common way that we deal with methane?

Answer 57

ventilate into sky

Question 58

What is the biological contributor of methane?

Answer 58

methanogenesis process

Question 59

Is the methanogenesis process aerobic or anaerobic?

Answer 59

anaerobic

Question 60

What are the 4 common places/environments is methane found?

Answer 60

wetlands, soil in anaerobic environments, landfills, guts of: cows, termites, humans

Question 61

What are methanogens?

Answer 61

strictly ARCHAEAL microbes than can produce methane

Question 62

How are methanogens autotrophic?

Answer 62

takes hydrogen and CO2 = make methane and water

Question 63

How are methanogens heterotrophic?

Answer 63

uses acetate, methanol, formate = make methane

Question 64

Are there any bacterial species known to produce methane?

Answer 64

no

Question 65

What are methanotrophs?

Answer 65

strictly bacteria that use methane as carbon source and energy via methane oxidation

Question 66

In which environment do methanotrophs live: aerobic or anaerobic?

Answer 66

aerobic ONLY

Question 67

What enzyme do methanotrophs use to oxidize methane?

Answer 67

methane monooxygenase

Question 68

What are the 3 intermediate molecules formed during methane oxidation?

Answer 68

methanol, formaldehyde, formic acid