3 free questions from this chapter (the full set has 30). Marking: +4 for correct · −1 for incorrect · 0 for unattempted.
Question 1Level 3 · AdvancedSingle correct
Consider the following statements on the development of the cell theory.
(i) Matthias Schleiden, a German botanist, observed that all plants are composed of different kinds of cells which form the tissues of the plant.
(ii) Theodore Schwann (1839) reported that animal cells have a thin outer layer, today known as the plasma membrane.
(iii) Based on his studies of plant tissues, Schwann concluded that the presence of a cell wall is a unique character of plant cells.
(iv) The cell theory as formulated by Schleiden and Schwann explained how new cells are formed.
(v) Rudolf Virchow (1855) explained that cells divide and new cells are formed from pre-existing cells.
How many of the above statements are correct?
Show answer and solution
Answer: D
Key insight: NCERT explicitly says the Schleiden-Schwann cell theory did NOT explain how new cells were formed. (i) Correct: Schleiden (1838), German botanist, noted plants are made of different kinds of cells forming tissues. (ii) Correct: Schwann (1839) reported the thin outer layer now called the plasma membrane. (iii) Correct: Schwann concluded, from plant tissue studies, that the cell wall is unique to plant cells. (iv) Incorrect: this was the gap in their theory; it is the trap statement because students attribute the whole modern theory to them. (v) Correct: Virchow (1855) gave Omnis cellula-e cellula and gave the cell theory its final shape. Hence 4 statements are correct.
Exam pattern: NEET – statement counting on history of cell theoryQuestion 2Level 2 · ExamSingle correct
Arrange the following in increasing order of their size as given in NCERT: P. a cell of Mycoplasma; Q. the average diameter of a mitochondrion; R. the diameter of a human red blood cell; S. a prokaryotic ribosome (about 15 nm by 20 nm).
AS < Q < P < R
BP < Q < S < R
CP < S < Q < R
DS < P < Q < R
Show answer and solution
Answer: D
Convert everything to micrometres first: S, the 70S ribosome, is 15-20 nm, i.e. 0.015-0.02 µm, the smallest. P, Mycoplasma, the smallest cell, is about 0.3 µm. Q, the mitochondrion, has a diameter of 0.2-1.0 µm with an average of 0.5 µm, just above Mycoplasma. R, the human RBC, is about 7.0 µm in diameter. So S < P < Q < R. Options C and B both misjudge nanometres against micrometres, placing the 15-20 nm ribosome above the 0.3 µm Mycoplasma (C) or even above the mitochondrion (B); option A reverses Mycoplasma and the mitochondrion (a common trap, since a 'whole cell' is assumed to be larger than an organelle).
Exam pattern: NEET – size comparison of cells and organelles (NCERT dimensions)Question 3Level 3 · AdvancedSingle correct
Match List I (prokaryotic structure) with List II (description as per NCERT).
List I: (a) Plasmid (b) Chromatophores (c) Fimbriae (d) Capsule
List II: (i) Thick and tough form of glycocalyx (ii) Membranous extensions into the cytoplasm containing pigments in cyanobacteria (iii) Small circular DNA outside the genomic DNA that may confer resistance to antibiotics (iv) Small bristle-like fibres that help bacteria attach to rocks in streams and to host tissues
Choose the correct option.
Aa-ii, b-iii, c-iv, d-i
Ba-iii, b-ii, c-i, d-iv
Ca-iii, b-iv, c-ii, d-i
Da-iii, b-ii, c-iv, d-i
Show answer and solution
Answer: D
Plasmids are small circular DNA outside the genomic DNA, conferring unique phenotypic characters such as antibiotic resistance; they are also used to monitor bacterial transformation, so a-iii. Chromatophores are membranous extensions into the cytoplasm of cyanobacteria containing pigments, so b-ii. Fimbriae are small bristle-like fibres sprouting out of the cell that help attachment to rocks in streams and host tissues, so c-iv. A glycocalyx that is thick and tough is called a capsule (a loose sheath is a slime layer), so d-i. Option C swaps fimbriae with chromatophores; option A wrongly calls the plasmid a pigment-bearing structure; option B swaps fimbriae and capsule.
Exam pattern: NEET – match the following on prokaryotic cell structures