CBSE Class 11 Biology – Mineral Nutrition | MCQs with Answers & Explanations (NCERT Based)

Course & Examination Details

Course: CBSE Class 11 Biology
Unit: Unit IV – Plant Physiology
Chapter: Chapter 12 – Mineral Nutrition
Prescribed Textbook: NCERT
Board: CBSE

CBSE Board Examination Relevance

• MCQs test conceptual clarity, application, and NCERT terminology
• Widely used in school exams, unit tests, and internal assessments
• All questions are framed strictly as per NCERT content

Section A: Essential Elements (MCQs 1–15)

Q1. Which of the following best defines an essential element?

A. An element required in large quantity
B. An element present in soil
C. An element indispensable for completion of plant life cycle
D. An element enhancing plant growth

Correct Answer: C
Explanation: An essential element is indispensable for completion of the life cycle and cannot be replaced by another element.

Q2. The criteria of essentiality were proposed by:

A. Dixon and Joly
B. Sachs
C. Arnon and Stout
D. Calvin

Correct Answer: C
Explanation: Arnon and Stout proposed the criteria to identify essential mineral elements in plants.

Q3. Which of the following is a macronutrient?

A. Iron
B. Zinc
C. Nitrogen
D. Copper

Correct Answer: C
Explanation: Nitrogen is required in large amounts and is classified as a macronutrient.

Q4. Which element is a constituent of chlorophyll?

A. Iron
B. Magnesium
C. Nitrogen
D. Calcium

Correct Answer: B
Explanation: Magnesium forms the central atom of the chlorophyll molecule.

Q5. Which macronutrient is essential for ATP formation?

A. Potassium
B. Phosphorus
C. Sulphur
D. Calcium

Correct Answer: B
Explanation: Phosphorus is a component of ATP and is essential for energy transfer reactions.

Q6. Potassium plays a major role in:

A. Cell wall formation
B. Enzyme activation and stomatal regulation
C. Chlorophyll synthesis
D. Nitrogen fixation

Correct Answer: B
Explanation: Potassium activates enzymes and regulates osmotic balance and stomatal movement.

Q7. Which element is required for cell wall stability?

A. Magnesium
B. Nitrogen
C. Calcium
D. Iron

Correct Answer: C
Explanation: Calcium is essential for cell wall formation and membrane integrity.

Q8. Sulphur is a component of:

A. Chlorophyll
B. ATP
C. Sulphur-containing amino acids
D. Cellulose

Correct Answer: C
Explanation: Sulphur is part of amino acids like cysteine and methionine.

Q9. Which of the following is a micronutrient?

A. Potassium
B. Phosphorus
C. Magnesium
D. Zinc

Correct Answer: D
Explanation: Zinc is required in trace amounts and acts as an enzyme activator.

Q10. Which micronutrient is involved in nitrogen metabolism?

A. Boron
B. Iron
C. Molybdenum
D. Chlorine

Correct Answer: C
Explanation: Molybdenum is a component of nitrate reductase and nitrogenase enzymes.

Q11. Functional classification of nutrients includes all EXCEPT:

A. Structural components
B. Enzyme activators
C. Energy carriers
D. Ionic balance maintainers

Correct Answer: C
Explanation: Energy carriers are not a separate functional category in NCERT classification.

Q12. Which element activates enzymes of respiration?

A. Magnesium
B. Iron
C. Chlorine
D. Sulphur

Correct Answer: A
Explanation: Magnesium acts as an activator of many respiratory enzymes.

Q13. Which element maintains osmotic balance in cells?

A. Calcium
B. Potassium
C. Sulphur
D. Iron

Correct Answer: B
Explanation: Potassium helps maintain osmotic balance and turgidity.

Q14. Beneficial elements are those that:

A. Are essential for all plants
B. Replace essential elements
C. Improve growth in some plants
D. Are toxic at low concentration

Correct Answer: C
Explanation: Beneficial elements are not essential but improve growth in some species.

Q15. Sodium is considered a:

A. Macronutrient
B. Micronutrient
C. Essential element
D. Beneficial element

Correct Answer: D
Explanation: Sodium is beneficial for some plants but not universally essential.

Section B: Deficiency Symptoms (MCQs 16–30)

Q16. Deficiency symptoms appear first in older leaves for:

A. Calcium
B. Iron
C. Nitrogen
D. Sulphur

Correct Answer: C
Explanation: Nitrogen is mobile and moves from older to younger leaves.

Q17. Chlorosis is caused due to deficiency of:

A. Nitrogen
B. Magnesium
C. Iron
D. All of the above

Correct Answer: D
Explanation: All listed elements are involved in chlorophyll synthesis or function.

Q18. Interveinal chlorosis is characteristic of deficiency of:

A. Nitrogen
B. Magnesium
C. Calcium
D. Sulphur

Correct Answer: B
Explanation: Magnesium deficiency causes interveinal chlorosis, especially in older leaves.

Q19. Necrosis refers to:

A. Yellowing of leaves
B. Reduced growth
C. Death of tissues
D. Delayed flowering

Correct Answer: C
Explanation: Necrosis is the death of plant tissues forming brown patches.

Q20. Which element deficiency causes death of root tips?

A. Nitrogen
B. Potassium
C. Calcium
D. Iron

Correct Answer: C
Explanation: Calcium is essential for meristematic tissue growth.

Q21. Iron deficiency symptoms appear in:

A. Older leaves
B. Young leaves
C. Roots
D. Stems

Correct Answer: B
Explanation: Iron is immobile; hence deficiency appears in young leaves.

Q22. Potassium deficiency results in:

A. Interveinal chlorosis
B. Marginal leaf necrosis
C. Death of meristems
D. Purple leaves

Correct Answer: B
Explanation: Potassium deficiency causes marginal necrosis of leaves.

Q23. Which deficiency delays flowering?

A. Phosphorus
B. Nitrogen
C. Calcium
D. Iron

Correct Answer: B
Explanation: Nitrogen deficiency reduces vegetative growth and delays flowering.

Q24. Mineral toxicity refers to:

A. Lack of minerals
B. Excess accumulation of minerals
C. Balanced nutrition
D. Deficiency of micronutrients

Correct Answer: B
Explanation: Excess of certain minerals can interfere with plant metabolism.

Q25. Excess manganese causes deficiency of:

A. Nitrogen
B. Iron
C. Calcium
D. Sulphur

Correct Answer: B
Explanation: Manganese toxicity inhibits iron absorption.

Q26. Which symptom is reversible in early deficiency?

A. Necrosis
B. Tissue death
C. Chlorosis
D. Meristem death

Correct Answer: C
Explanation: Chlorosis can be reversed if nutrients are supplied early.

Q27. Why are deficiency symptoms specific?

A. Elements act randomly
B. Each element has unique role
C. Soil type varies
D. Climate varies

Correct Answer: B
Explanation: Each nutrient performs specific metabolic functions.

Q28. Which element deficiency causes poor root development?

A. Phosphorus
B. Iron
C. Magnesium
D. Chlorine

Correct Answer: A
Explanation: Phosphorus is essential for root growth and energy transfer.

Q29. Toxicity usually occurs due to excess of:

A. Macronutrients
B. Micronutrients
C. Carbon
D. Hydrogen

Correct Answer: B
Explanation: Micronutrients are required in trace amounts and easily become toxic.

Q30. Nutrient mobility affects:

A. Rate of photosynthesis
B. Site of deficiency symptoms
C. Soil fertility
D. Root absorption

Correct Answer: B
Explanation: Mobility determines whether symptoms appear in old or young leaves.

Section C: Nitrogen Cycle & Biological Nitrogen Fixation (MCQs 31–50)

Q31. Atmospheric nitrogen is unavailable to plants because it is:

A. Scarce
B. Inert
C. Soluble
D. Toxic

Correct Answer: B
Explanation: Nitrogen exists as inert N₂ gas and must be fixed.

Q32. Conversion of N₂ into ammonia is called:

A. Nitrification
B. Ammonification
C. Nitrogen fixation
D. Denitrification

Correct Answer: C
Explanation: Nitrogen fixation makes nitrogen usable for plants.

Q33. Which organism fixes nitrogen symbiotically?

A. Azotobacter
B. Nostoc
C. Rhizobium
D. Nitrosomonas

Correct Answer: C
Explanation: Rhizobium forms root nodules in legumes.

Q34. Nitrification converts ammonia into:

A. Nitrogen gas
B. Nitrate
C. Amino acids
D. Proteins

Correct Answer: B
Explanation: Nitrification produces nitrites and nitrates.

Q35. Nitrosomonas converts ammonia into:

A. Nitrate
B. Nitrogen
C. Nitrite
D. Urea

Correct Answer: C

Q36. Denitrification results in:

A. Increase in soil nitrogen
B. Loss of nitrogen from soil
C. Nitrogen fixation
D. Protein synthesis

Correct Answer: B

Q37. Which bacteria perform denitrification?

A. Rhizobium
B. Azotobacter
C. Pseudomonas
D. Nitrobacter

Correct Answer: C

Q38. Decomposition of organic nitrogen into ammonia is:

A. Nitrification
B. Ammonification
C. Assimilation
D. Fixation

Correct Answer: B

Q39. Nitrogenase enzyme is sensitive to:

A. Light
B. Carbon dioxide
C. Oxygen
D. Water

Correct Answer: C

Q40. Leghaemoglobin is found in:

A. Leaves
B. Roots
C. Root nodules
D. Stems

Correct Answer: C

Q41. Function of leghaemoglobin is to:

A. Fix nitrogen
B. Transport oxygen
C. Maintain low oxygen level
D. Absorb nitrates

Correct Answer: C

Q42. Which free-living organism fixes nitrogen?

A. Rhizobium
B. Azotobacter
C. Nitrobacter
D. Pseudomonas

Correct Answer: B

Q43. Which form of nitrogen is absorbed by plants?

A. N₂
B. NH₃ only
C. Nitrate and ammonium
D. Urea

Correct Answer: C

Q44. Nitrogen assimilation results in formation of:

A. Nitrates
B. Nitrites
C. Amino acids
D. Nitrogen gas

Correct Answer: C

Q45. Which enzyme converts nitrate to nitrite in plants?

A. Nitrogenase
B. Nitrate reductase
C. Nitrite reductase
D. Dehydrogenase

Correct Answer: B

Q46. Biological nitrogen fixation requires:

A. Oxygen
B. ATP and reducing power
C. Carbon dioxide
D. Chlorophyll

Correct Answer: B

Q47. Which practice improves soil fertility naturally?

A. Monocropping
B. Heavy fertilizer use
C. Growing legumes
D. Over-irrigation

Correct Answer: C

Q48. Nitrogen cycle maintains:

A. Soil pH
B. Water balance
C. Nitrogen balance in nature
D. Temperature

Correct Answer: C

Q49. Excessive fertilizer use causes:

A. Improved fertility only
B. Nutrient imbalance and pollution
C. Increased nitrogen fixation
D. Reduced crop yield always

Correct Answer: B

Q50. Which process returns nitrogen to atmosphere?

A. Nitrification
B. Assimilation
C. Denitrification
D. Ammonification

Correct Answer: C

Best Suited For

• CBSE Class 11 Annual Examinations
• NCERT-based MCQ practice
• Concept clarification & revision

Targeting Exams

• CBSE Class 11 Biology Annual Examination

• CBSE School Unit Tests & Term Exams

• NCERT Chapter-wise MCQ Assessments

• Internal Assessments & Practice Tests

• Foundation preparation for Class 12 Biology

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