Q40. Which of the following possesses the largest isolated single cell?
[SSC MTS, 14 November 2024, Shift 2]
(a) Ostrich egg
(b) Human brain
(c) Amoeba
(d) Blue whale
Answer: (a) Ostrich egg
Explanation: The ostrich ovum is generally cited in school biology as the largest single cell visible without a microscope. A brain and a whale are multicellular organisms or structures, whereas an amoeba is a microscopic unicellular organism.
Q39. Which organelle in animal cells can digest foreign materials?
[UPSC CDS (II), General Knowledge 2024]
(a) Endoplasmic reticulum
(b) Lysosome
(c) Golgi body
(d) Mitochondria
Answer: (b) Lysosome
Explanation: Lysosomes receive foreign particles after uptake and digest them with hydrolytic enzymes. They also help recycle aged cellular components. The Golgi apparatus processes and sorts materials; mitochondria generate ATP; and endoplasmic reticulum participates in protein and lipid metabolism.
Q38. Which of the following causes enlargement and extension growth of plant cells?
[SSC CHSL Tier I, 8 July 2024, Shift 1]
(a) Turgor pressure
(b) Imbibition
(c) Pressure potential
(d) Osmotic pressure
Answer: (a) Turgor pressure
Explanation: As water enters a plant cell, the expanding vacuole raises turgor pressure against the cell wall. When the wall can loosen and extend, this pressure drives cell enlargement. Turgor also supports herbaceous tissues and reduces wilting.
Q37. In which year did Rudolf Virchow formulate the aphorism “Omnis cellula e cellula”?
[SSC CHSL Tier I, 17 August 2023, Shift 4]
(a) 1855
(b) 1869
(c) 1840
(d) 1835
Answer: (a) 1855
Explanation: In 1855, Rudolf Virchow advanced the concept that cells arise from pre-existing cells. This concept became a major principle of cell theory and clarified continuity between generations of cells through cell division instead of spontaneous formation.
Q36. Which cell organelle is known as the cell’s post office?
[SSC CHSL Tier I, 14 August 2023, Shift 1]
(a) Nucleus
(b) Golgi apparatus
(c) Ribosome
(d) Plastid
Answer: (b) Golgi apparatus
Explanation: The Golgi apparatus modifies, sorts and packages proteins and lipids into transport vesicles. Because it directs cellular products to their destinations, it is compared to a post office. Its stacks of flattened membrane sacs are called cisternae.
Q35. Which part of a cell converts nutrients into energy?
[SSC CHSL Tier I, 3 August 2023, Shift 2]
(a) Cell membrane
(b) Lysosomes
(c) Mitochondria
(d) Chromosome
Answer: (c) Mitochondria
Explanation: Mitochondria convert energy released by nutrient oxidation into ATP during aerobic respiration. The Krebs cycle occurs in the matrix, and the electron-transport system functions in the inner membrane. This energy-producing role explains the expression powerhouse of the cell.
Q34. Which is the primary structural component responsible for most mechanical strength of a plant cell wall?
[SSC MTS, 8 September 2023, Shift 1]
(a) Heparin
(b) Glycogen
(c) Chitin
(d) Cellulose
Answer: (d) Cellulose
Explanation: Cellulose chains aggregate into strong microfibrils that provide tensile strength to plant cell walls. Hemicelluloses and pectins contribute to the surrounding matrix. Chitin instead reinforces fungal walls, while glycogen serves mainly as an energy-storage polysaccharide.
Q33. In which year did Robert Hooke introduce the term “cell”?
[SSC MTS, 1 September 2023, Shift 2]
(a) 1875
(b) 1675
(c) 1665
(d) 1765
Answer: (c) 1665
Explanation: Hooke used the word cell in 1665 after observing cork tissue. Its small compartments reminded him of little rooms. He presented the observation in Micrographia, establishing an important historical starting point for the microscopic study of living structures.
Q32. Cell wall is absent in which one of the following organisms?
[UPSC CDS (II), General Knowledge 2023]
(a) Bacteria
(b) Diatom
(c) Mushroom
(d) Tapeworm
Answer: (d) Tapeworm
Explanation: Tapeworms are animals, and animal cells do not have rigid walls outside their plasma membranes. Bacteria generally possess peptidoglycan walls, mushrooms have fungal walls rich in chitin, and diatoms have silica-rich protective coverings called frustules.
Q31. If human red blood cells are placed in normal saline isotonic to blood, what happens?
[UPSC CDS (I), General Knowledge 2023]
(a) They swell
(b) They swell and burst
(c) They shrink
(d) Their diameter remains unchanged
Answer: (d) Their diameter remains unchanged
Explanation: An isotonic medium has approximately the same effective osmotic concentration as the red-cell interior. Water continues to cross the membrane in both directions, but there is no net movement. The cells therefore retain their normal size.
