Assertion (A): Xylem vessels are dead at maturity. Reason (R): Lignin deposition provides strength but blocks cytoplasm, leading to cell death. MCQ with Answer and Explanation
Assertion (A): Xylem vessels are dead at maturity.
Reason (R): Lignin deposition provides strength but blocks cytoplasm, leading to cell death.
A. Both A and R are true, but R is not the correct explanation.
B. Both A and R are true, and R is the correct explanation.
C. A true, R false.
D. A false, R true.
Answer: Option B
Solution (By JKExamLibrary)
Xylem tracheids and vessels develop lignified secondary walls and lose protoplasm, becoming dead tubes efficient for water conduction. R correctly explains A.
Explanation:
Sulfur is present in the amino acids methionine and cysteine (which forms disulfide bonds in proteins). Nitrogen is in all amino acids, phosphorus in nucleic acids and ATP, iron in heme. Sulfur is also in vitamins biotin and thiamine. Disulfide bonds are crucial for protein tertiary structure.
Explanation:
Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis, spreading through airborne droplets. Cancer, diabetes, and hypertension are non-communicable.
Explanation:
Actin (thin) and myosin (thick) filaments slide past each other during contraction, powered by ATP. Collagen is structural, hemoglobin transports oxygen.
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