Assimilation of Inorganic Nutrients - 8

Question 1

Define Nutrient Assimilation

Answer 1

energy-requiring process which plants incorporate inorganic nutrients into the carbon constituents necessary for growth and development

Question 2

What does acquiring nitrogen from the atmosphere require (nitrogen fixation)

Answer 2

breaking the stable triple covalent bond between two nitrogen atoms to produce ammonia or nitrate

Question 3

Define the Haber-bosh process

Answer 3

is the starting point for the manufacture of many industrial and agricultural products (including nitrogen fertilizers)

Question 4

How is ammonia formed

Answer 4

N2 combines with hydrogen to form ammonia, under elevated temperatures and high pressure in the presence of a metal catalyst (usually iron)

Question 5

What are the 3 processes that fix 190 million metric tons per year of nitrogen

Answer 5

1. lightning
2. photochemical reactions
3. biological nitrogen fixation (90%)

Question 6

Once fixed into ammonia or nitrate…

Answer 6

nitrogen enters biogeochemical cycle through several organic and inorganic forms before returning to molecular nitrogen

Question 7

at high concentrations, ____ is toxic to living tissues, while ____ can be safely stored and translocated in plant tissues

Answer 7

ammonium
nitrate

Question 8

Explain nitrate assimilation

Answer 8

plant roots absorb nitrate from soil solution, and assimilate most into organic nitrogen compounds

Question 9

Define nitrogen reductase

Answer 9

main molybdenum-containing protein in vegetative tissues. it catalyzes first step in nitrate assimilation

Question 10

what influences nitrate reductase at the transcription and translation level

Answer 10

nitrate, light and carbohydrates

Question 11

nitrate reductase is also subject to _____ involving a reversible phosphorylation

Answer 11

post-translational modification

Question 12

What inactivates nitrogen reductase

Answer 12

darkness and Mg 2+

Question 13

what provides the highest amount of regulation of nitrate reductase activity

Answer 13

phosphorylation and dephosphorylation provides rapid control

Question 14

Function of nitrite reductase

Answer 14

converts nitrite into ammonium, highly reactive

Question 15

What happens after plants generate nitrite generated from nitrate reduction

Answer 15

it is transported from the cytosol to the chloroplasts and plastids (leaves and shoots)

Question 16

Where is nitrite reductase encoded and synthesized

Answer 16

encoded in nucleus
synthesized in cytoplasm with N-terminal transit peptide

Question 17

What induces transcription of nitrite reductase

Answer 17

elevated concentrations of nitrite or exposure to light

Question 18

nitrate is reduced primarily in the ______, as supply increases nitrate is translocated to the ____

Answer 18

roots
shoots

Question 19

how do plants cells amount ammonium toxicity

Answer 19

by rapidly converting the ammonium generated from nitrate assimilation or photorespirations in amino acids

Question 20

The primary pathway of ammonium assimilation involves the sequential actions of _____ and _____

Answer 20

glutamine synthetase and glutamate synthetase

Question 21

Define glutamate synthetase (GS)

Answer 21

combines ammonium with glutamate to form glutamine
involves divalent cation and ATP

Question 22

Where are the two classes of GS located in plants
and which is more affected by carbs and light

Answer 22

one in cytosol and one in plastids
plastid

Question 23

elevated levels of ____ stimulate the activity of glutamate synthetase

Answer 23

glutamine - two forms
in non-photosynthetic tissue and in photosynthetic tissues

Question 24

Define glutamate dehydrogenase (GDH)

Answer 24

catalyzes a reversible reaction that synthesizes or deaminates glutamate

Question 25

ammonium can be assimilated via ______ used for _____ of nitrogen

Answer 25

an alternative pathway
re-allocation

Question 26

once assimilated into glutamine and glutamate, nitrogen is incorporated into ______ via _____
ex.

Answer 26

amino acids
transamination reactions
aspartate aminotransferase

Question 27

all transamination reactions require ______

Answer 27

pyridoxal phosphate