8) NO, (nitrate) is taken up into roots, and needs to be converted to NIL and th

Question

8) NO, (nitrate) is taken up into roots, and needs to be converted to NIL and then assimilated into amino acids. Much of this occurs in root plastids, and requires a lot of energy. From where does the root plastid get this required energy? C) The Calvin cycle B) Glycolysis E) oxidative pentose phosphate pathway D) The light reactions The enzyme that converts toxic nitrite to ammonia, and is found in the chloroplast of leaves or the plastids of root is 9) A) Nitrogenase B) Nitrate reductase C) Ammonia synthase D) Nitrite reductase E) Glutamate dehydrogenase 10) The legume/thizobium interaction is a symbiosis. How do these organisms mutually benefit each other? (2 pts) I1) The legume/rhizobium interaction is a mutually beneficial symbiosis important to nutrient cycling in the environment. If it is beneficial to both organisms, why do not all plants do it? (1 pt) 12) The majority of organic material in the biosphere is in the cell walls of plants (living or dead) A) TRUE B) FALSE 13) Indicate where each of the following cell wall components is made prior to incorporation into the final cell wall complex outside the plasma membrane. (% pt each; 2 pts total) Cellulose Hemicellulose Pectins cell wall proteins (hint: most proteins destined for secretion outside the cell are translated here) 14) Which is NOT a function of plant cell walls A) Provides structural support to plants B) Constrain the size and shape of the cell C) Constrain turgor (hydrostatic) pressure of the cell D) Provide photoassimilate to the cell E) Provide a barrier against pathogens Which statement is true regarding cell wall polysaccharides A) Lignin is a (1 ?4)f-D-glucan chain with many side branches B) Pectin is a (1>4)B-D-glucan chain with no side branches C) Cellulose is a (1>4)B-D-glucan chain with many side branches D) Cellulose is a (194)6-D-glucan chain with no side branches E) Hemicellulose is a (1->4)ß-D-glucan chain with no side branches 15) Which component of the primary cell wall contributes most to the cell's structural rigidity: A) cellulose 16) B) hemicelluloses C) pectins D) lignin E) peptidoglycans Which component is usually only found in secondary cell walls: A) cellulose 17) B) hemicelluloses C) pectins D) lignin E) peptidoglycans

Explanation / Answer

8. Correct answer is option E – Oxidative pentose phosphate pathway.

Reason: Oxidative pentose phosphate pathway takes place in plastids and it produces 12 molecules of NADPH2 which is equivalent to 36 ATP molecules. Glycolysis produces 2 NADH and 2 ATP molecules. Calvin cycle is a catabolic reaction and in this process, energy is utilized. Light reactions do not take place in root plastids. Rhizobia utilizes energy produced from plants. So, the correct answer is option E – Oxidative pentose phosphate pathway.

9. The correct answer is option D – Nitrite reductase

Explanation: Nitrite reductase is present in the stroma of plants. Using six electron reduction steps, it catalyzes the conversion of nitrite to ammonia. The main cofactor of this enzyme is copper.

10. A symbiosis is a form of mutualism in which species involved are mutually benefitted. The symbiotic interaction between leguminous plants and rhizobia have the following advantages:

a. Rhizobium species fix inorganic nitrogen into ammonia and leguminous plants supply nutrients such organic carbon and oxygen for the growth of bacteria

b. Rhizobium species promotes the growth of legumes in the phosphorous deficient soil. This, in turn, supports the growth of rhizobia.

c. Rhizobia also improves the nitrogen levels in plants and this further stimulates the growth of mycorrhizal species on the legume roots. These factors increase the yield of leguminous plants.

11. Leguminous plants secrete chemicals called flavonoids which attracts the rhizobia to colonize the roots of these plants. These flavonoids are released only by leguminous plants. Hence, all plants do not attract rhizobia.

12. True - The cell wall of plants is made up of cellulose, hemicellulose, pectin etc. These are all organic compounds and hence majority of organic material are in the cell wall of living and dead plants.

13. Cellulose – Plasma membrane by cellulose synthase complex

Hemicellulose – Golgi complex

Pectin – Golgi vesicles

Cell wall proteins - Ribosomes

14. The correct answer is option D - Provide photoassimilate to the cell.

Reason: Photoassimilation is provided by chloroplasts

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