16. Assimilation of Nitrogen

Question 1

nitrogen is the __ most abundant element in a plant

Answer 1

4th

Question 2

plants use only 2 forms of N:

Answer 2

NH4+ (ammonium) and NO3- (nitrate)

Question 3

3 main ways nitrogen enters biosphere:

Answer 3

biological fixation
anthropogenically (haber-bosch process)
lightning - atmosphere

Question 4

why is haber-bosch process important?

Answer 4

accounts for 50% of all nitrogen fixation globally, but also 2% of all FF consumption

allowed for an agricultural boom, green revolution, fertilizers, allows agricultural production necessary for supporting world pop.
also, requires a LOT of energy

Question 5

N2 has a ___ bond, which means:

Answer 5

triple ; it is very difficult to break, requires huge input of energy

Question 6

atmospheric N becomes bioavailable
N2 + ___ –> ___

Answer 6

N2 + 3 H2 –> 2NH3

Question 7

biological fixation of N is only possible in:

Answer 7

prokaryotes

Question 8

2 types of bacteria impt for N assimilation:

Answer 8

rhizobia
actinobacteria

Question 9

rhizobia have a symbiosis with:

Answer 9

legumes

Question 10

actinobacteria have a symbiosis with:

Answer 10

actinorhizal plants

Question 11

examples of legumes

Answer 11

soybeans, peas, lentils, alfalfa

Question 12

N assimilating bacteria form:

Answer 12

nodules on roots

Question 13

enzyme responsible for N assimilation

Answer 13

nitrogenase

Question 14

nitrogenase is tricky because:

Answer 14

it is inhibited by O2

Question 15

how do bacteria get around oxygen inhibition?

Answer 15

leghemoglobin binds to oxygen and carries oxygen away from nitrogenase

Question 16

leghemoglobin

Answer 16

myoglobin-like protein that binds to oxygen and transports it away from nitrogenase towards bacteroids that use it for respiration

Question 17

peribacteroid membrane

Answer 17

permeable barrier that separates respiring symbiotic cells and nitrogenase to maintain proper oxygen levels

Question 18

what causes the meaty taste in impossible burgers?

Answer 18

leghemoglobin

Question 19

5 steps in the formation of a nodule

Answer 19

1. communication between bacteria and root hair
2. root hair curling around bacteria
3. infection thread formation, bacteria spreads throughout root hair
4. cell division in root
5. leghemoglobin expressed in nodule