Botany 2023 Paper II 50 marks Explain

Q8

(a) (i) How do the three stages in fatty acid oxidation converge to conserve energy as ATP ? 5 (ii) What is β-oxidation ? Describe various steps in fatty acid oxidation pathway involving saturated fatty acids. 15 (b) Explain the transfer of energy between different trophic levels of an ecosystem. 15 (c) What are the major gaseous pollutants and their sources ? Explain the effects of air pollutants on human health. 15

हिंदी में प्रश्न पढ़ें

(a) (i) ए.टी.पी. (ATP) के रूप में ऊर्जा के संरक्षण के लिए वसा अम्ल ऑक्सीकरण में तीन चरण कैसे अभिसरण करते हैं ? 5 (ii) बीटा-ऑक्सीकरण क्या है ? संतृप्त वसा अम्लों से युक्त वसा अम्ल ऑक्सीकरण मार्ग के विभिन्न चरणों का वर्णन कीजिए । 15 (b) पारिस्थितिकी तंत्र में विभिन्न पोषी स्तरों के मध्य ऊर्जा के स्थानांतरण को समझाइए । 15 (c) प्रमुख गैसीय प्रदूषक एवं उनके स्रोत क्या हैं ? मानव स्वास्थ्य पर वायु प्रदूषकों के प्रभावों की व्याख्या कीजिए । 15

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Directive word: Explain

This question asks you to explain. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

See our UPSC directive words guide for a full breakdown of how to respond to each command word.

How this answer will be evaluated

Approach

The directive 'explain' demands clear, logical exposition with cause-effect linkages. Structure: brief introduction linking metabolic efficiency to ecosystem function and environmental health; for (a)(i) allocate ~80 words on convergence of β-oxidation, Krebs cycle and ETC to ATP yield; for (a)(ii) allocate ~250 words with diagram on β-oxidation steps; for (b) allocate ~250 words on energy transfer with 10% law and ecological pyramids; for (c) allocate ~250 words on gaseous pollutants with Indian examples like Delhi smog, Bhopal disaster context; conclude with integrated remark on metabolic-ecosystem-human health nexus.

Key points expected

  • (a)(i) Three stages: β-oxidation producing NADH/FADH₂, Krebs cycle oxidation, ETC phosphorylation; stoichiometry showing ~106 ATP per palmitate (or corrected modern value ~80-90 ATP)
  • (a)(ii) Definition of β-oxidation as mitochondrial process; four steps: oxidation by FAD-dependent acyl-CoA dehydrogenase, hydration by enoyl-CoA hydratase, oxidation by NAD⁺-dependent β-hydroxyacyl-CoA dehydrogenase, thiolysis by β-ketothiolase; acetyl-CoA entry into Krebs cycle
  • (b) Trophic levels: producers, primary consumers, secondary consumers, tertiary consumers; 10% energy transfer law (Lindeman); ecological pyramids (number, biomass, energy); energy loss via respiration, heat, undigested matter, decomposition
  • (c) Major gaseous pollutants: SO₂ (thermal power plants, smelters), NOₓ (vehicles, combustion), CO (incomplete combustion), O₃ (photochemical smog), CO₂ (fossil fuels), NH₃ (agriculture); Indian sources: Delhi-NCR vehicular emissions, coal-based NTPC plants, stubble burning in Punjab-Haryana
  • (c) Health effects: SO₂/NOₓ → respiratory irritation, bronchitis, asthma; CO → carboxyhaemoglobin, hypoxia; O₃ → lung damage, reduced immunity; particulate matter association with cardiovascular disease; reference to WHO guidelines and Indian NAAQS

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Precise biochemical stoichiometry for (a) including correct ATP yield calculations; accurate 10% law with Lindeman's trophic efficiency concept for (b); correct chemical formulae and mechanism-based health effects for (c); no confusion between β-oxidation and ω-oxidationGenerally correct concepts but muddled ATP arithmetic or vague on trophic efficiency percentages; minor errors in pollutant chemistry (e.g., confusing NO with NO₂) or generic health effects without mechanismFundamental errors: states β-oxidation occurs in cytoplasm; reverses energy pyramid direction; confuses primary and secondary pollutants; attributes CO₂ toxicity directly rather than asphyxiation
Diagram / labelling15%7.5Clear hand-drawn style diagram for β-oxidation spiral showing fatty acid activation, carnitine shuttle, four enzymatic steps with cofactors; OR energy pyramid diagram with correct trophic level proportions; OR pollution source-pathway-receptor diagram; all structures labelled with proper nomenclatureDiagram present but incomplete labelling, missing key enzymes (e.g., thiolase) or cofactors; pyramid drawn without quantitative scale; pollution diagram lacks directional arrowsNo diagram despite clear visual demand; or diagram with major errors (e.g., showing β-oxidation in peroxisome without distinction, inverted pyramid for energy)
Examples & nomenclature20%10Specific Indian ecosystem examples: Sundarbans mangrove energy flow, Gir forest trophic structure; specific pollution episodes: 1984 Bhopal (methyl isocyanate though not gaseous, shows awareness), Delhi 2019 smog, Chennai thermal plant emissions; correct IUPAC names for fatty acids and enzymesGeneric ecosystem examples (grassland, pond) without Indian specificity; standard pollutants listed without source attribution to Indian cities; common names used instead of systematic nomenclatureNo Indian examples; invented or incorrect episode references; confusion between common and scientific names; misspelled enzyme names (e.g., 'dehydrogenaze')
Process explanation25%12.5Stepwise mechanistic clarity: for (a)(ii) details substrate channeling, carnitine shuttle regulation, and stoichiometric coupling to ETC; for (b) explains why energy transfer is inefficient (thermodynamic, ecological, metabolic losses); for (c) describes photochemical smog formation mechanism (NO₂ photolysis, radical chain reactions)Lists steps without mechanistic linkage; states 'energy is lost' without explaining respiratory quotient or heat dissipation; describes pollution effects without formation chemistryDescriptive only, no process logic; confuses activation energy with energy yield; attributes smog solely to SO₂ ignoring NOₓ-photochemistry; no mention of regulatory mechanisms (e.g., malonyl-CoA inhibition of CPT-I)
Application / ecology15%7.5Integrative conclusion linking fatty acid metabolism efficiency to ecosystem productivity constraints and human metabolic disease (obesity, diabetes); connects air pollution to crop yield reduction (O₃ damage to C₃ plants like wheat/rice) and food security; mentions bioremediation or policy (BS-VI norms, National Clean Air Programme)Separate treatment of parts without synthesis; brief mention of environmental impact without specific crop or health policy linkageNo application dimension; treats biochemistry, ecology and pollution as isolated silos; no mention of relevance to agriculture, health policy, or environmental management

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