#Question id: 10347
#Unit 6. System Physiology – Plant
NH4+ is toxic to plants, inhibit dinitrogenase and also interfere energy metabolism by dissociating ATP formation from ETC in both mitochondria and chloroplasts. What will plant cells do to avoid this problem?
a) Plant cells avoid ammonium toxicity by rapidly converting the ammonium generated from nitrate assimilation or photorespiration into nitrate
b) Plant cells avoid ammonium toxicity by rapidly converting the ammonium generated from nitrate assimilation or photorespiration into amino acids
c) The pathway for this conversion involves the sequential actions of glutamine synthetase (GS) and glutamate synthase (GOGAT)
d) The pathway for this conversion involves the sequential actions of Aspartate aminotransferase (Asp-AT) and Asparagine synthetase (AS)
Which of the above statements is incorrect?
#Question id: 10348
#Unit 6. System Physiology – Plant
During ammonium assimilation, requires two enzymes converting ammonium to amino acids. Each of which is Glutamine synthetase (GS), given below some statements about GS ;
a) GS transfers the amide group of glutamine to 2-oxoglutarate, yielding two molecules of glutamate
b) it requires a divalent cation such as Mg2+, Mn2+, or Co2+ as a cofactor
c) Plants contain two classes of GS, one in the cytosol and the other in root plastids or shoot chloroplasts
d) The cytosolic forms are expressed in germinating seeds or in the vascular bundles of roots and shoots and produce glutamate for intercellular nitrogen transport
e) The GS in root plastids generates amide nitrogen for local consumption; the GS in shoot chloroplasts reassimilates photorespiratory NH4+
f) Light and carbohydrate levels alter the expression of the cytosolic forms of the enzyme, but they have little effect on the plastid forms.
Which of the following statements is correct?
#Question id: 10349
#Unit 6. System Physiology – Plant
Elevated plastid levels of glutamine stimulate the activity of glutamate synthase (also known as glutamine:2- oxoglutarate aminotransferase, or GOGAT). Given below some of the statements about GOGAT, which one of the following is incorrect?
#Question id: 10350
#Unit 6. System Physiology – Plant
Ammonium can be assimilated via an alternative pathway rather than primary pathway which involves the sequential actions of glutamine synthetase(GS) and glutamate synthase(GOGAT), these alternative pathway catalyzes by enzyme known as,
#Question id: 10351
#Unit 6. System Physiology – Plant
Plants contain two types of GOGAT; one accepts electrons from NADH, and the other accepts electrons from ferredoxin (Fd); which one of the following statements is correct?
#Question id: 10352
#Unit 6. System Physiology – Plant
which of the following amino acid that participates in the malate–aspartate shuttle to transfer reducing equivalents from the mitochondrion and chloroplast into the cytosol?