NEET Biology Mineral Nutrition Important Questions Set 02

These Class 11 NEET Biology important questions on Mineral Nutrition give 21 questions with step-by-step answers, arranged as very short, short and long answer types, taken from a model test paper. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. How many ATP molecules are spent for production of one molecule of ammonia in N₂-fixation?
Answer: 8

Question 2. Name the mineral element required in the synthesis of auxin.
Answer: Zinc

Question 3. Name the ionic form in which boron is absorbed by the plant roots from the soil.
Answer: BO33– or B₄O72–

Question 4. Why the central portion of root nodules appear pinkish in colour?
Answer: Due to the presence of a red or pink-coloured pigment called leghaemoglobin.

Question 5. What is the role of Nitrosomonas in nitrogen cycle?
Answer: It is a nitrifying bacteria which oxidizes ammonia to form nitrites. 2NH₃ + 3O₂ —Nitrosomonas→ 2NO₂− + 2H+ + 2H₂O + Energy

Question 6. List two mineral elements responsible for necrosis in plants.
Answer: Ca and Mg

Short Answer Type Questions

Question 7. Differentiate between macro and micronutrients on the basis of :
(i) Concentration in plants
(ii) Major function
Answer: Macronutrients Micronutrients Concentration The concentration of a macro The concentration of a micro element per gram of dry–1 matter is element–1 is less than 10 millimole atleast 10 millimole kg of the dry kg ofthedry matter. matter. Major function They are mainly structural in They are generally required in the function, i.e., they build up the plant functioning ofenzymes. body and different protoplasmic constituents.

Question 8. List two deficiency symptoms in plants.
Answer: (i) Chlorosis, i.e., loss of chlorophyll leading to yellowing in leaves.
(ii) Necrosis, i.e., death of leaf tissue.

Question 9. Write a short note on nitrification.

Answer:

Nitrification : The phenomenon of conversion of ammonium nitrogen to nitrate nitrogen is called nitrification. It is performed in two steps :
(i) In the first step, ammonia is oxidised to nitrites by the action of Nitrosomonas and/or Nitrococcus bacteria.

(ii) In the second step, nitrite is further oxidised to nitrate with the help of Nitrobacter and/or Nitrocystis. 2NO₂− + O₂ —Nitrobacter / → 2NO₃− + Energy Nitrocystis

Question 10. Give two examples of :
(i) Non-essential elements
(ii) Symbiotic N₂-fixing bacteria
Answer: (i) Sodium and cobalt
(ii) Rhizobium and Frankia

Question 11. Why do root nodules appear pinkish in colour? What is its significance?

Answer:

Root nodules appear pinkish in colour because of the presence of a red or pink-coloured pigment called leghaemoglobin.

This pigment acts as O₂ scavenger and thus create anaerobic conditions essential for the functioning of nitrogenase enzyme.

Short Answer Type Questions

Question 12. What is Hydroponics? Give its significance (two points) in agriculture.

Answer:

The soil-less growth of plants in a nutrient solution is called Hydroponics.

Significance :

(i) Hydroponics is used for commercial production of vegetables such as tomato, seedless cucumber, lettuce etc.

(ii) Culture experiments can also be used to identify whether an element is essential or not. They help in finding out the role of an essential element in structure and function of plants. We can also discover the symptoms of deficiency and absence of an essential element.

Question 13. (i) Is phosphorus a macro or microelement? In which form is it absorbed by plants?
(ii) Give two functions of phosphorus in plants.

Answer:

(i) It is a macroelement, absorbed in the form of phosphate ions (H₂PO4– or HPO42–) from the soil.
(ii) Physiological role :

(1) Phosphorus is a constituent of cell membranes, certain proteins, nucleotides, nucleic acids (DNA and RNA), ATP, NADP and nucleoproteins.

(2) It is required for all phosphorylation reactions. ATP contains energy-rich phosphate bonds.

Question 14. Draw a labelled diagram of nitrogen cycle.

Answer:

A well-labelled diagram should show these parts: Atmospheric N2; NH; NO2–; NO3–; 3; Soil 'N' Pool; (Ammonification); (Uptake); Decaying biomass; Plant biomass; Animal biomass.

Question 15. Describe any two physiological roles and one deficiency symptom of iron in plants.
Answer: Physiological role : (any two)
(i) It is an important constituent of proteins involved₂₊ in the transfer of electrons like ferredoxin and cytochromes. It is reversibly oxidised from Fe to Fe³⁺ during electron transfer in photosynthesis and respiration.
(ii) It activates catalase and some other enzymes.
(iii) It is essential for the formation of chlorophyll and other pigments. Deficiency symptom : Deficiency of iron causes chlorosis as it is essential for the formation of chlorophyll pigment.

Question 16. (i) What do you mean by toxic concentration of an element?
(ii) What are the toxic effects of manganese on plants?
Answer: (i) Any micronutrient ion concentration in tissues that reduces the dry weight of tissues by about 10% is called its toxic concentration.
(ii) Toxic effects of Mn are :
(1) Reduction in uptake of Mg and Fe.
(2) Prevention of binding of Mg with enzymes.
(3) Inhibition of Ca translocation to shoot apex.

Question 17. Describe the ways by which ammonia is assimilated to form amino acids in plants.

Answer:

There are two main ways by which NH4+ is assimilated to form amino acids in plants :
1. Reductive amination : In the presence of dehydrogenase (e.g., Glutamate Dehydrogenase), ammonium ion directly combines with an organic acid (e.g., α-Ketoglutaric acid), to form an amino acid (Glutamic acid). A reduced coenzyme (NADPH) is required. α-Ketoglutaric acid + NH+₄ + NADPH —→Glutamate Glutamate + H₂O + NADP Dehydrogenase

2. Transamination : It involves the transfer of amino group ( CHNH₂) of one amino acid to the keto group ( C = O) of keto acid. The enzyme required is transaminase or aminotransferase. Glutamic acid is the primary amino acid from which the transfer of amino group (–NH₂) takes place and other amino acids are formed through transamination.

Question 18. Identify the following :
(i) Element that forms the core constituent of the ring structure of chlorophyll.
(ii) Element that is involved in pollen germination.
(iii) Element that is required in the synthesis of auxin.
Answer: (i) Magnesium
(ii) Boron
(iii) Zinc

Question 19. Write short notes on :
(i) Biological nitrogen fixation
(ii) Amides

Answer:

(i) Biological nitrogen-fixation : Reduction of inert atmospheric nitrogen to ammonia by living organisms is called biological nitrogen-fixation. Only certain prokaryotic organisms (some bacteria and cyanobacteria/ blue-green algae) are capable of fixing N₂. Such microbes are called N₂-fixers. These N₂-fixing microbes contain an exclusive enzyme, nitrogenase that is capable of reducing nitrogen. N₂ —NitrogenaseN → NH₃ -fixers 2 The nitrogen-fixing microbes could be free-living or symbiotic in nature.
(ii) Amides : They are organic compounds derived from amino acids in which hydroxyl component (–OH) of carboxylic group (–COOH) is replaced by another amino group (–NH₂). As a result, amides have more nitrogen than amino acid. The two most important amides are aspargine and glutamine. They are formed by amidation of glutamic acid and aspartic acid respectively. For instance,

Synthetase Glutamine and aspargine are a structural part of plant proteins alongwith amino acids. These amides perform two other functions – storage of excess nitrogen and transport.

Long Answer Type Questions

Question 20. (i) Name the enzyme present in Rhizobium that is responsible for N₂-fixation. Briefly explain.
(ii) Also discuss the steps involved in the mechanism of N₂-fixation.

Answer:

(i) The enzyme, nitrogenase is responsible for fixing atmospheric nitrogen (N ≡ N). It is present only in prokaryotes. It is a Mo-Fe protein that catalyses the conversion of atmospheric nitrogen into ammonia. It is highly sensitive to the molecular oxygen, therefore, it requires anaerobic conditions for functioning.
(ii) Steps involved in N₂-fixation : A nitrogen molecule (N ≡ N) gets attached to Mo-Fe component. The molecule of nitrogen is reduced by the addition of hydrogen atoms (provided by a reducing agent like NADPH₂) Substrate Product [nitrogen gas (N )] [ammonia (NH3)] 2

Reduction

Reduction Reduction Releaseof products

Enzyme Binding H +2 H +2 H (nitrogenase) of substrate ⁺² Freecan nitrogenase bind anotherof N molecule 2

It produces dimide (N₂H₂), hydrazine (N₂H₄) and finally ammonia (2NH₃) is formed. The synthesis of ammonia requires very high input of energy (8 ATP for each NH₃ produced). The energy required is obtained from the respiration of the host cells. The overall reaction involved is N₂ + 8e− + 8H+ + 16ATP —→ 2NH₃ + H₂ + 16ADP + 16Pi

Question 21. (i) What are essential mineral elements? How many elements are essential for plants? Make a list of them.
(ii) Also describe the mechanism of absorption of these elements.

Answer:

(i) Essential mineral elements are the elements which have a specific structural or physiological role and without which plants cannot complete their life cycle. 17 elements have been found to be essential for plants. These are C, H, O, N, P, K, Ca, Mg, S, B, Mo, Mn, Ni, Cl, Fe, Cu and Zn.
(ii) Plants absorb the essential mineral nutrients from the soil through their roots. The most active areas of the root for mineral absorption are the zones of elongation and root hairs. The minerals are actively absorbed as ions and get accumulated by the plants against their concentration in the soil. Studies have revealed that the process of mineral absorption can be demarcated into two main phases
– initial and metabolic. These phases are discussed below :
(1) In the initial phase, there is a rapid uptake of ions into the outer or free space of the cells (i.e., the area of apoplast). Outer or free space comprises intercellular spaces and cell walls. In this phase, the ions are absorbed passively, i.e., energy is not spent. The passive movement of ions into the apoplast usually occurs through ion channels.
(2) Metabolic phase : In the metabolic phase, the ions pass into inner space (i.e., the symplast area of the cells). The inner space comprises cytoplasm and vacuole. In this phase, the movement of ions is an active process, i.e., the entry or exit of ions to and from the inner space requires the expenditure of metabolic energy.