Cell: The Unit of Life — NEET 2027 | 39 PYQs, Free Bilingual Practice

Which of the following is not a feature of the plasmids?

1. A. Independent replication
2. B. Circular structure
3. C. Transferable
4. D. Single – stranded

Explanation: Answer: (D) Single – stranded Solution: Plasmids are small circular DNA molecules present outside the genomic DNA in many bacteria; like all DNA they are double-stranded, not single-stranded, so this is not a feature. Plasmids replicate independently, are circular, and can be transferred (used to monitor bacterial transformation with foreign DNA), making options 1, 2 and 3 valid features. Hence the odd one out is "single-stranded." NCERT Reference: Ch 8, p.90, lines 10–16: "many bacteria have small circular DNA outside the genomic DNA. These smaller DNA are called plasmids. The plasmid DNA confers certain unique phenotypic characters to such bacteria."

Select the wrong statement

1. A. Bacteria cell wall is made up of peptidoglycan
2. B. Pili and fimbriae are mainly involved in motility of bacterial cells
3. C. Cyanobacteria lack flagellated cells
4. D. Mycoplasma is a wall – less microorganism

Explanation: Answer: (B) Pili and fimbriae are mainly involved in motility of bacterial cells Solution: This is the wrong statement. NCERT explicitly states that besides flagella, pili and fimbriae are surface structures of bacteria but do not play a role in motility; motility is due to flagella. The other statements are correct: bacterial cell wall is peptidoglycan-based, cyanobacteria lack flagellated cells, and Mycoplasma is the wall-less prokaryote. NCERT Reference: Ch 8, p.91, lines 13-14: "Pili and Fimbriae are also surface structures of the bacteria but do not play a role in motility."

A cell organelle containing hydrolytic enzymes is

1. A. Lysosome
2. B. Microsome
3. C. Ribosome
4. D. Mesosome

Explanation: Answer: (A) Lysosome Solution: Lysosomes are membrane-bound vesicular structures very rich in almost all types of hydrolytic enzymes (hydrolases) that are optimally active at acidic pH. Microsomes and mesosomes are not defined by hydrolytic enzymes, and ribosomes are the site of protein synthesis. Therefore the organelle containing hydrolytic enzymes is the lysosome. NCERT Reference: Ch 8, p.96, lines 25–29: "These are membrane bound vesicular structures formed by the process of packaging in the golgi apparatus. The isolated lysosomal vesicles have been found to be very rich in almost all types of hydrolytic enzymes (hydrolases – lipases, proteases, carbohydrases) optimally active at the acidic pH."

Mitochondria and chloroplast are: (i) Semi – autonomous organelles (ii) Formed by division of pre – existing organelles and they contain DNA but lack protein synthesizing machinery Which one of the following options is correct?

1. A. Both (i) and (ii) are correct
2. B. (ii) is true but (i) is false
3. C. (i) is true but (ii) is false
4. D. Both (i) and (ii) are false

Explanation: Answer: (C) (i) is true but (ii) is false Solution: Mitochondria and chloroplasts are semi-autonomous organelles because both are double-membrane bound, contain their own circular DNA and 70S ribosomes, and divide by fission, so statement (i) is true. Statement (ii) is false: although they do contain DNA, they are NOT lacking protein-synthesising machinery — the mitochondrial matrix (and chloroplast stroma) possess ribosomes and the components required for protein synthesis. Hence only (i) is correct. NCERT Reference: Ch 8, p.97, lines 13–16: "The matrix also possesses single circular DNA molecule, a few RNA molecules, ribosomes (70S) and the components required for the synthesis of proteins. The mitochondria divide by fission."