Q60. In which of the following processes is active transport NOT used?
[UPSC CDS (II), General Knowledge 2026]
(a) Reabsorption of amino acids and glucose from kidney into blood
(b) Loading sugar from photosynthesizing leaf cells into phloem tissue for transportation
(c) Passage of Na⁺ and Cl⁻ through hydrophilic channels formed by protein molecules
(d) Absorption of glucose and electrolytes into the bloodstream
Answer: (c) Passage of Na⁺ and Cl⁻ through hydrophilic channels formed by protein molecules
Explanation: Ion passage through an open channel can occur by facilitated diffusion, following the electrochemical gradient without direct ATP consumption. By contrast, active transport moves substances against a gradient and needs energy, either directly or through coupling to another gradient.
Q59. Which one of the following is NOT true of mitotic cell division?
[UPSC CDS (II), General Knowledge 2026]
(a) The two daughter nuclei have the same number of chromosomes
(b) Mitosis enables replacement of cells and tissue repair
(c) Asexual reproduction in eukaryotes can occur through mitosis
(d) Cells become haploid as a result of mitosis
Answer: (d) Cells become haploid as a result of mitosis
Explanation: Mitosis ordinarily maintains the chromosome number of the parent cell, generating genetically similar daughter nuclei. Haploid cells arise through reduction division in meiosis instead. Mitosis supports growth, tissue repair and several forms of asexual reproduction in eukaryotes.
Q58. Which one of the following is NOT found in a prokaryotic cell?
[UPSC CDS (II), General Knowledge 2026]
(a) Cell wall
(b) Ribosome
(c) Nuclear membrane
(d) Plasmid DNA
Answer: (c) Nuclear membrane
Explanation: Prokaryotes lack a membrane-enclosed nucleus. Their principal chromosome occupies a nucleoid region, and extra circular DNA may occur as plasmids. They possess ribosomes for protein synthesis; many also have a cell wall, although some groups lack one.
Q57. Which material did Robert Hooke use to first discover “cells”?
[RRB Group D, 19 August 2026, Shift 2]
(a) Cork slice
(b) Human cheek
(c) Onion peel
(d) Leaf surface
Answer: (a) Cork slice
Explanation: Robert Hooke examined thin slices of cork using a microscope in 1665. He observed tiny boxlike compartments and named them cells. The compartments were dead plant cell walls; the discovery was later described in his influential book Micrographia.
Q56. Identify the correctly matched cell–structure pair.
[RRB Group D, 19 August 2026, Shift 3]
(a) Eukaryotic cell — membrane-bound endoplasmic reticulum
(b) Prokaryotic cell — mitochondria
(c) Animal cell — cell wall
(d) Bacterial cell — well-defined nucleus
Answer: (a) Eukaryotic cell — membrane-bound endoplasmic reticulum
Explanation: Eukaryotic cells possess internal membrane-bound organelles including the endoplasmic reticulum. Prokaryotes lack mitochondria and a true nucleus. Most animal cells lack cell walls; bacteria generally contain a cell wall but their chromosomal DNA lies in a nucleoid.
Q55. Which organelle is physically continuous with the nuclear envelope?
[RRB Group D, 20 August 2026, Shift 1]
(a) Endoplasmic reticulum
(b) Mitochondria
(c) Golgi body
(d) Lysosome
Answer: (a) Endoplasmic reticulum
Explanation: The outer nuclear membrane continues into the membrane of the endoplasmic reticulum, and the perinuclear space joins its lumen. This continuity connects nuclear organization with cellular production and processing of proteins and lipids, although other organelles remain separate structures.
Q54. The central cytoplasmic region of a prokaryotic cell containing nucleic acids is called:
[UPSC CDS (I), General Knowledge 2026]
(a) Nucleus
(b) Nucleoid
(c) Nucleolus
(d) Plastid
Answer: (b) Nucleoid
Explanation: The nucleoid is the DNA-containing area of bacterial and archaeal cells, without a surrounding nuclear envelope. Unlike the true nucleus of a eukaryotic cell, it is not membrane bound. The nucleolus is a subnuclear region associated with ribosome production.
Q53. The antibiotic penicillin can kill invading bacteria without harming human cells because it targets the bacterial:
[UPSC CDS (I), General Knowledge 2026]
(a) Cell wall
(b) Plasma membrane
(c) Ribosome
(d) Chromosome
Answer: (a) Cell wall
Explanation: Penicillin inhibits enzymes involved in cross-linking peptidoglycan, a vital component of many bacterial cell walls. Human cells have plasma membranes but no peptidoglycan walls. This difference explains penicillin’s selective action, especially against susceptible actively growing bacteria.
Q52. In which cell type is the highest number of lysosomes likely to occur?
[UPSC CDS (I), General Knowledge 2026]
(a) Pancreatic cell
(b) Ovarian cell
(c) Thigh muscle cell of a runner
(d) White blood cell
Answer: (d) White blood cell
Explanation: Phagocytic white blood cells ingest microorganisms and cellular debris, then fuse phagosomes with enzyme-containing lysosomes for destruction. Their intensive digestive activity explains their abundant lysosomal machinery. Muscle cells, by comparison, often have numerous mitochondria to meet energy demand.
Q51. A cell is damaged and its lysosomes burst, releasing digestive enzymes into the cytoplasm. What is most likely to happen?
[RRB Group D, 30 December 2025, Shift 2]
(a) The mitochondria produce more energy
(b) The cell grows in size
(c) The cell destroys itself and dies
(d) The nucleus divides rapidly
Answer: (c) The cell destroys itself and dies
Explanation: Lysosomes carry acid hydrolases that digest biological macromolecules. Severe lysosomal rupture can contribute to cellular self-digestion and injury. The term suicidal bags refers to this destructive potential, although ordinary programmed cell death involves more elaborate regulatory pathways.