Nitrate reductase is an important enzyme for nitrate assimilation. Given below some regulation of nitrate reductase activity through phosphorylation and dephosphorylation.

a) Light, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby activates the enzyme

b) In Dark, and Mg2+ stimulate a protein kinase that phosphorylates the same serine residues, which then interact with a 14-3-3 inhibitor protein, and thereby inactivate nitrate reductase

c) In Light, and Mg2+ stimulate a protein kinase that phosphorylates the serine residues, and thereby activate nitrate reductase

d) In Dark, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby inactivates the enzyme

Which of the following statements about regulation of nitrate reductase is correct?

#Question id: 10361

#Unit 6. System Physiology – Plant

The carbon skeleton for amino acids derives from 3-phosphoglycerate generated during glycolysis is called anaplueratic reaction. Generated amino acids from 3-PGA is that,

#Question id: 10360

#Unit 6. System Physiology – Plant

How much ATP require in the nitrogen fixation or conversion of ammonium assimilation in the system?

#Question id: 10357

#Unit 6. System Physiology – Plant

Why the glutamine and glutamate will not be transported while  asparagine will prefer to be transported?

#Question id: 10356

#Unit 6. System Physiology – Plant

Why the GS  and GOGAT is activated in light and while the AS is inhibited?

#Question id: 10354

#Unit 6. System Physiology – Plant

One of the enzyme that are involve in the ammonium assimilation is Asparagine synthetase (AS), some statements given below about AS such as,

a) This enzyme that catalyzes this reaction, is found in the cytosol of leaves and roots and in nitrogen-fixing nodules

b) High levels of light and carbohydrate inhibit the expression of genes coding for AS and the activity of the enzyme

c) Conditions of ample energy stimulate AS, thus they favor nitrogen assimilation into glutamine and glutamate

d) Energy-limited conditions inhibit GS and GOGAT, stimulate AS, and thus favor nitrogen assimilation into asparagine, a compound that is rich in nitrogen and sufficiently stable for long-distance transport or long term storage

Which of the following statements about AS is correct?

#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?