Q10. Which of the following is NOT a part of the breathing mechanism?
[UPSC NDA-I (22 April 2018)]
(a) Bronchi
(b) Bowman’s capsule
(c) Diaphragm
(d) Trachea
Answer: (B) Bowman’s capsule
Explanation: Bowman’s capsule is part of a kidney nephron, surrounding the glomerulus where blood filtration begins. Bronchi and trachea conduct air, and the diaphragm is the primary inspiratory muscle. Thus only Bowman’s capsule belongs to the urinary rather than respiratory system.
Q9. What are the overall end-products of aerobic respiration?
[RPSC (1 July 2017)]
(a) Carbon dioxide, water and energy
(b) Carbon dioxide and energy only
(c) Sugar, energy and water
(d) Oxygen, carbon dioxide and water
Answer: (A) Carbon dioxide, water and energy
Explanation: Complete aerobic oxidation of glucose produces carbon dioxide and water and releases energy, much of which cells capture as ATP. Carbon dioxide arises primarily during pyruvate oxidation and the citric acid cycle; oxygen is consumed at the electron transport chain.
Q8. Which pathway is common to aerobic respiration and alcoholic fermentation?
[RPSC (1 July 2017)]
(a) Fermentation itself
(b) Oxidative phosphorylation
(c) Glycolysis
(d) Citric acid cycle
Answer: (C) Glycolysis
Explanation: Glycolysis is the shared cytosolic pathway that converts glucose into pyruvate. With oxygen, pyruvate undergoes further oxidation and the respiratory electron transport chain can produce additional ATP. Under alcoholic fermentation, pyruvate is converted into ethanol and carbon dioxide.
Q7. Which organelle is chiefly associated with aerobic cellular respiration?
[UPPSC Staff Nurse Examination (December 2017)]
(a) Glyoxysomes
(b) Ribosomes
(c) Lysosomes
(d) Mitochondria
Answer: (D) Mitochondria
Explanation: Mitochondria perform pyruvate oxidation, the Krebs cycle and oxidative phosphorylation in aerobic eukaryotic cells. Glycolysis nevertheless occurs in the cytoplasm, so not every respiratory reaction is mitochondrial. Ribosomes synthesise proteins, while lysosomes chiefly participate in intracellular digestion.
Q6. Mammals respire by which principal organs?
[MPPSC Preliminary Examination (2016)]
(a) Gills
(b) Trachea alone
(c) Skin
(d) Lungs
Answer: (D) Lungs
Explanation: Mammals exchange respiratory gases in their lungs, where extensive alveolar surfaces support diffusion between air and blood. They ventilate the lungs using breathing muscles, notably the diaphragm. Gills are typical of fish and some aquatic invertebrates, not mammals.
Q5. Bacteria that can survive and grow both in the presence and absence of free oxygen are known as what?
[RPSC Assistant Engineer Examination (2016)]
(a) Facultative anaerobes
(b) Obligate aerobes
(c) Obligate anaerobes
(d) Non-pathogenic bacteria
Answer: (A) Facultative anaerobes
Explanation: Facultative anaerobes can use oxygen-dependent respiration when oxygen is available but switch to anaerobic energy pathways when it is absent. Obligate aerobes require oxygen, while obligate anaerobes grow without it and may be harmed by exposure to oxygen.
Q4. Which processes add carbon dioxide to Earth’s carbon cycle?
1. Volcanic action
2. Respiration
3. Photosynthesis
4. Decay of organic matter.
[UPSC Civil Services Preliminary Examination (2014)]
(a) 1 and 3 only
(b) 2 only
(c) 1, 2 and 4 only
(d) 1, 2, 3 and 4
Answer: (C) 1, 2 and 4 only
Explanation: Respiration releases carbon dioxide as organic carbon is oxidised; decomposers also release it during breakdown of dead material, and volcanic activity emits geological carbon dioxide. Photosynthesis instead usually removes carbon dioxide from the atmosphere by fixing it into organic compounds.
Q3. Birds differ from bats in the absence of which structure?
[WBCS Preliminary Examination (2013)]
(a) Warm blood
(b) Four-chambered heart
(c) Trachea
(d) Diaphragm
Answer: (D) Diaphragm
Explanation: Birds lack a muscular diaphragm and ventilate relatively rigid lungs using movements of the rib cage and air sacs. Bats are mammals and use a diaphragm for breathing. Both groups are warm-blooded vertebrates with a trachea and four-chambered heart.
Q2. Consider: 1. Photosynthesis 2. Respiration 3. Decay of organic matter 4. Volcanic action. Which add carbon dioxide to Earth’s carbon cycle?
[UPSC Civil Services Preliminary Examination (2011)]
(a) 1 and 4 only
(b) 2 and 3 only
(c) 2, 3 and 4 only
(d) 1, 2, 3 and 4
Answer: (C) 2, 3 and 4 only
Explanation: Carbon dioxide enters the atmosphere through cellular respiration, biological decomposition and volcanic emissions. Green plant photosynthesis fixes atmospheric carbon dioxide into carbohydrates instead. The question tests the direction of carbon transfer, not whether a process involves carbon molecules.
Q1. The proportion of which air component remains almost unchanged between inhalation and exhalation during ordinary human respiration?
[RAS/RTS Preliminary Examination (2003)]
(a) Carbon dioxide
(b) Oxygen
(c) Water vapour
(d) Nitrogen
Answer: (D) Nitrogen
Explanation: Inhaled and exhaled air differ mainly in oxygen, carbon dioxide and moisture. Nitrogen is largely physiologically inert under normal breathing conditions and undergoes negligible net exchange, so its proportion stays nearly the same. Small percentage variations may reflect changes in other gases.
