Q20. Which statements correctly describe differences between plant and animal cells?
1. Plant cells have cellulose walls, animal cells do not.
2. Plant cells lack plasma membranes.
3. Mature plant cells generally have one large vacuole, animal cells may have small vacuoles.
[UPSC Civil Services Preliminary Examination 2020]
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c) 1 and 3 only
Explanation: Plant cells possess both a cellulose-rich cell wall and an underlying plasma membrane. Their large central vacuole commonly maintains turgor. Animal cells lack cellulose walls and may have small vacuoles. Therefore statements one and three are correct, but two is false.
Q19. Which is the energy currency for cellular processes?
[UPSC CDS (I), General Knowledge 2020]
(a) Glucose
(b) ATP
(c) ADP
(d) Pyruvic acid
Answer: (b) ATP
Explanation: ATP stores readily transferable energy in phosphoanhydride bonds and couples energy-releasing reactions to cellular work. Hydrolysis to ADP and inorganic phosphate powers many biological processes. Glucose is a metabolic fuel, whereas ATP is the immediate energy-transfer molecule.
Q18. Which one of the following best defines active transport?
[UPSC CDS (II), General Knowledge 2019]
(a) Movement against a diffusion gradient using energy from respiration
(b) Movement against a diffusion gradient without energy
(c) Movement against a diffusion gradient using energy from photosynthesis only
(d) Movement along a diffusion gradient using energy from respiration
Answer: (a) Movement against a diffusion gradient using energy from respiration
Explanation: Active transport moves substances against their concentration or electrochemical gradients and therefore requires energy. ATP made during cellular respiration commonly powers membrane transporters either directly or indirectly. Simple diffusion and facilitated diffusion ordinarily proceed down a gradient.
Q17. In photosynthetic prokaryotic bacteria, chlorophyll is associated with:
[UPSC CDS (II), General Knowledge 2019]
(a) Plastids
(b) Membranous vesicles
(c) Nucleoids
(d) Chromosomes
Answer: (b) Membranous vesicles
Explanation: Photosynthetic bacteria do not possess the membrane-bound chloroplasts of plants. Their photosynthetic pigments occur in internal or specialized membranes. These membranes carry the systems that capture light energy; the nucleoid instead stores chromosomal DNA and does not act as a chloroplast.
Q16. Which function is NOT carried out by smooth endoplasmic reticulum?
[UPSC CDS (I), General Knowledge 2019]
(a) Transport of materials
(b) Synthesis of lipids
(c) Synthesis of proteins
(d) Synthesis of steroid hormones
Answer: (c) Synthesis of proteins
Explanation: Smooth ER contributes to lipid and steroid synthesis and other metabolic tasks. Because it lacks attached ribosomes, it is not the main site of protein translation. Proteins intended for secretion are commonly made by ribosomes on rough endoplasmic reticulum.
Q15. Which organelle is NOT found in prokaryotic cells?
[UPSC NDA (I), General Ability Test, 22 April 2018]
(a) Cell wall
(b) Mitochondria
(c) Plasma membrane
(d) Ribosome
Answer: (b) Mitochondria
Explanation: Prokaryotes such as bacteria have plasma membranes, cytoplasmic ribosomes and often cell walls. They do not possess membrane-bound mitochondria. Cellular respiration can occur through their cytoplasmic membrane and associated enzyme systems instead of a separate mitochondrial organelle.
Q14. The cell walls of many fungi are composed of which tough complex sugar?
[SSC CHSL, 14 March 2018, Shift 2]
(a) Pectin
(b) Suberin
(c) Cellulose
(d) Chitin
Answer: (d) Chitin
Explanation: Chitin is a strong nitrogen-containing polysaccharide that reinforces fungal cell walls. Plant walls are primarily cellulose-based, whereas pectin forms part of their wall matrix. Chitin also appears in arthropod exoskeletons and gives mechanical strength to biological structures.
Q13. Which of the following is NOT a feature found in almost every cell?
[SSC CHSL, 16 March 2018, Shift 2]
(a) Cell wall
(b) Plasma membrane
(c) Nucleus
(d) Cytoplasm
Answer: (a) Cell wall
Explanation: Cell walls occur in plants, fungi and many prokaryotes but are absent from animal cells. A plasma membrane and cytoplasm are basic cellular features. The nucleus is not universal either, because prokaryotes lack one; the intended contrast here concerns walls.
Q12. Which process does NOT occur inside mitochondria?
[RPSC Senior Teacher Grade II (Science), 1 November 2018]
(a) Krebs cycle
(b) Glycolysis
(c) ATP synthesis
(d) Electron transport chain
Answer: (b) Glycolysis
Explanation: Glycolysis occurs in the cytosol, where glucose is converted to pyruvate. The mitochondrial matrix supports the Krebs cycle, while the inner membrane contains the electron-transport system and ATP synthase. Mitochondria therefore perform later stages of aerobic respiration.
Q11. Which among the following does not have a cell wall?
[SSC CGL Tier I, 11 August 2017, Shift 3]
(a) Euglena
(b) Paramecium
(c) Gonyaulax
(d) Mycoplasma
Answer: (d) Mycoplasma
Explanation: The official key identifies Mycoplasma, a bacterium without a peptidoglycan wall. However, the wording is scientifically ambiguous: Euglena and Paramecium also lack conventional cell walls. The keyed response should therefore be understood as the examination answer, not a unique biological distinction.
