NEET Biology Mineral Nutrition MCQs Set 16

Answer: (d) Phosphorus, potassium, sulphur, calcium

Explanation:
1. All four of phosphorus, potassium, sulphur and calcium are macronutrients.
2. Each of the other options includes at least one micronutrient or non-essential element.

Teacher's Note:
1. Macronutrients: C, H, O, N, P, K, Ca, Mg, S.

Answer: (b) Leghaemoglobin

Explanation:
1. Leghaemoglobin scavenges free oxygen in the nodules.
2. Cytochromes, xanthophyll and carotene have no such role.

Teacher's Note:
1. Leghaemoglobin gives the pink colour to active nodules.

Answer: (b) Manganese and chlorine

Explanation:
1. Splitting of water needs Mn and Cl as cofactors of the oxygen-evolving complex.
2. Magnesium, potassium and molybdenum are not part of this complex.

Teacher's Note:
1. Mn and Cl are the two elements for photolysis.

Answer: (a) Ca

Explanation:
1. Calcium is needed for the formation of the mitotic spindle and for the cell wall.
2. It is therefore required in meristems such as the root tip.

Teacher's Note:
1. Ca deficiency stops cell division at the meristems.

Answer: (c) Pseudomonas and Thiobacillus

Explanation:
1. Pseudomonas and Thiobacillus convert nitrate to free nitrogen.
2. Nitrosomonas and Nitrobacter are nitrifying bacteria.

Teacher's Note:
1. Denitrification reduces soil fertility.

Answer: (a) P, N, K and Mg

Explanation:
1. Phosphorus, nitrogen, potassium and magnesium are all macronutrients.
2. Mn, Fe, Co and Si are needed in trace amounts or are only beneficial.

Teacher's Note:
1. Eliminate options containing Mn or Fe.

Answer: (a) B, Ni, Mo, Mn, Fe

Explanation:
1. Boron, nickel, molybdenum, manganese and iron are all micronutrients.
2. The other sets include N, P, S, Ca, K or Mg, which are macronutrients.

Teacher's Note:
1. The eight micronutrients are Fe, Mn, Cu, Zn, B, Mo, Cl and Ni.

Answer: (c) Nitrosomonas and Nitrococcus

Explanation:
1. Nitrosomonas and Nitrococcus oxidise ammonia to nitrite.
2. Nitrobacter oxidises nitrite to nitrate, and the other organisms are not nitrifiers.

Teacher's Note:
1. Both oxidation steps together make nitrification.

Answer: (a) Rhodospirillum : mycorrhiza

Explanation:
1. Rhodospirillum is a free-living nitrogen-fixing photosynthetic bacterium and does not form mycorrhiza.
2. The other three pairs are correct.

Teacher's Note:
1. Mycorrhiza is a fungus-root association, as in Glomus.

Answer: (a) Ferric

Explanation:
1. Plants absorb iron mainly as ferric ions (Fe³⁺), as per NCERT.
2. It is not absorbed as the free element.

Teacher's Note:
1. Iron is needed for chlorophyll synthesis and for cytochromes.

Answer: (c) Potassium

Explanation:
1. Potassium maintains the osmotic potential and anion-cation balance of cells.
2. It also controls stomatal opening and so helps keep cells turgid.

Teacher's Note:
1. K⁺ accumulates in guard cells during stomatal opening.

Answer: (a) Nostoc, Oscillatoria, Anabaena

Explanation:
1. Nostoc, Oscillatoria and Anabaena are cyanobacteria (blue-green algae) that fix nitrogen.
2. The other options mix fern, bacteria and actinomycetes.

Teacher's Note:
1. Cyanobacteria are the only autotrophic nitrogen fixers.

Answer: (a) A-ii, B-iii, C-i, D-iv

Explanation:
1. Magnesium activates PEP carboxylase, so A matches ii.
2. Zinc activates alcohol dehydrogenase, so B matches iii.
3. Iron is needed for catalase, so C matches i.
4. Molybdenum is part of nitrogenase, so D matches iv.

Teacher's Note:
1. Match the cofactor with its enzyme: Mg with carboxylases, Zn with alcohol dehydrogenase and carbonic anhydrase, Fe with catalase and cytochromes.
2. Mo is the cofactor of nitrate reductase and nitrogenase.

Answer: (c) Their concentration is below 10 millimole per kg of dry weight

Explanation:
1. Micronutrients or trace elements are present at less than 10 mmole per kg of dry weight.
2. Macronutrients are present at more than 10 mmole per kg.

Teacher's Note:
1. 10 mmole per kg dry weight is the dividing line between macro and micronutrients.

Answer: (b) Azotobacter and Rhizobium

Explanation:
1. Azotobacter fixes nitrogen as a free-living aerobic bacterium.
2. Rhizobium fixes nitrogen only in symbiosis with legume roots.

Teacher's Note:
1. Glomus is a mycorrhizal fungus and does not fix nitrogen.

Answer: (d) Azotobacter, Nostoc, Beijerinckia

Explanation:
1. Azotobacter, Beijerinckia and Nostoc fix nitrogen in the free-living state.
2. Rhizobium and Frankia are symbiotic, and Glomus does not fix nitrogen.

Teacher's Note:
1. Learn the free-living list: Azotobacter, Beijerinckia, Clostridium, Nostoc, Anabaena.

Answer: (d) Examples are N, P, Zn, Mn, Mo

Explanation:
1. Nitrogen and phosphorus are macronutrients, not micronutrients.
2. The other statements correctly describe micronutrients.

Teacher's Note:
1. Zn, Mn and Mo are micronutrients, but N and P are not.

Answer: (b) Mo

Explanation:
1. Molybdenum is a component of nitrogenase, the enzyme of nitrogen fixation.
2. Mg, Zn and Cu do not take part in this reaction.

Teacher's Note:
1. Mo and Fe are present in nitrogenase.

Answer: (a) Cysteine

Explanation:
1. Cysteine has a thiol (-SH) group in its side chain.
2. Asparagine, glutamic acid and tryptophan have no sulphur.

Teacher's Note:
1. Cysteine and methionine are the two sulphur-containing protein amino acids.

Answer: (d) Frankia

Explanation:
1. Frankia forms nodules on roots of non-legumes such as Alnus and Casuarina.
2. Rhizobium nodulates legumes, while Azotobacter and Rhodospirillum are free-living.

Teacher's Note:
1. Frankia is an actinomycete.

Answer: (c) Formation of chlorophyll

Explanation:
1. Calcium forms calcium pectate in the middle lamella, helps in spindle formation and keeps membranes working normally.
2. Chlorophyll contains magnesium, not calcium.

Teacher's Note:
1. Ca also activates some enzymes such as amylase.

Answer: (d) All of the above

Explanation:
1. Excess manganese competes with Fe and Mg for uptake and inhibits translocation of Ca to the shoot apex.
2. So it produces deficiency symptoms of all three.

Teacher's Note:
1. Toxicity of one element may appear as deficiency of another.

Answer: (c) Both Rhizobium and Frankia

Explanation:
1. Both Rhizobium and Frankia live free in soil but fix nitrogen only when in symbiosis with plant roots.
2. Azotobacter is free living and fixes nitrogen without a host.

Teacher's Note:
1. Free-living fixers and symbiotic fixers differ in needing a host plant.

Answer: (d) All of the above

Explanation:
1. Deficiency of nitrogen, sulphur and molybdenum all delay flowering.
2. So all three options are correct.

Teacher's Note:
1. NCERT lists N, S and Mo as elements whose low level delays flowering.

Answer: (c) Na, Se, Si, Co

Explanation:
1. Sodium, selenium, silicon and cobalt are beneficial elements needed by some plants.
2. The other options include essential elements such as K, Cl, Ca and N.

Teacher's Note:
1. Beneficial elements are not essential for all plants but help some of them.