Which scientist is credited with the discovery of the cell nucleus?
A. Antonie van Leeuwenhoek
B. Robert Brown
C. Robert Hooke
D. Rudolf Virchow
Answer: Option B
Solution (By JKSSB Mock Tests)
Robert Brown, a Scottish botanist, first described the nucleus in 1831 while studying epidermal cells of orchids. Hooke discovered cells, Leeuwenhoek observed living cells, Virchow proposed that cells arise from pre-existing cells. Brown's discovery was pivotal for understanding cellular organization.
Explanation:
Translation is the ribosome-mediated synthesis of a polypeptide chain according to the mRNA template. tRNA molecules bring amino acids, and peptide bonds form. Replication duplicates DNA, transcription synthesizes RNA from DNA, transformation is genetic uptake by bacteria.
Assertion (A): The bacterial cell wall is composed of peptidoglycan.
Reason (R): Peptidoglycan provides structural strength and prevents osmotic lysis.
A.Both A and R are true, but R is not the correct explanation.
B.A false, R true.
C.A true, R false.
D.Both A and R are true, and R is the correct explanation.
Explanation:
Bacterial cell walls contain peptidoglycan (murein), a unique polymer that maintains cell shape and protects against osmotic pressure. The reason correctly explains why peptidoglycan is essential.
No comments yet. Be the first to start the discussion!