CSIR NET Life Sciences System Physiology - Plant Syllabus

System Physiology - Plant syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for System Physiology - Plant in CSIR NET Life Sciences, not a summary of it.

1. 1

   Photosynthesis

   4 topics

   • Light Harvesting Complexes
   • Electron Transport Mechanisms
   • Photoprotective Mechanisms
   • CO2 Fixation - C3, C4 and CAM Pathways
2. 2

   Respiration and Photorespiration

   4 topics

   • Citric Acid Cycle
   • Plant Mitochondrial Electron Transport and ATP Synthesis
   • Alternate Oxidase
   • Photorespiratory Pathway
3. 3

   Nitrogen Metabolism

   2 topics

   • Nitrate and Ammonium Assimilation
   • Amino Acid Biosynthesis
4. 4

   Plant Hormones

   4 topics

   • Biosynthesis
   • Storage
   • Breakdown and Transport
   • Physiological Effects and Mechanisms of Action
5. 5

   Sensory Photobiology

   4 topics

   • Structure, Function and Mechanisms of Action of Phytochromes
   • Cryptochromes and Phototropins
   • Stomatal Movement
   • Photoperiodism and Biological Clocks
6. 6

   Solute Transport and Photoassimilate Translocation

   3 topics

   • Uptake, Transport and Translocation of Water, Ions, Solutes and Macromolecules
   • Transpiration
   • Mechanisms of Loading and Unloading of Photoassimilates
7. 7

   Secondary Metabolites

   3 topics

   • Biosynthesis of Terpenes
   • Phenols and Nitrogenous Compounds
   • Roles of Secondary Metabolites
8. 8

   Stress Physiology

   2 topics

   • Responses of Plants to Biotic Stresses (Pathogen and Insects)
   • Responses of Plants to Abiotic Stresses (Water, Temperature and Salt)

System Physiology - Plant flashcards for CSIR NET Life Sciences

24 of 65 cards from the System Physiology - Plant deck — real questions with worked answers.

1. What are the two main types of light-harvesting complexes (LHC) in plants and which photosystems do they serve?

   LHC-I (associated with Photosystem I) and LHC-II (associated with Photosystem II). LHC-II is the most abundant membrane protein on Earth and binds chlorophyll a, chlorophyll b, and carotenoids.

2. In photosynthesis, what is the function of antenna (light-harvesting) pigments versus the reaction center?

   Antenna pigments absorb light and transfer excitation energy by resonance (Forster) transfer to the reaction center, where the special chlorophyll pair performs the actual photochemical charge separation (electron donation).

3. Name the reaction center chlorophyll pairs of Photosystem I and Photosystem II and their absorption maxima.

   PSI reaction center is P700 (absorbs ~700 nm); PSII reaction center is P680 (absorbs ~680 nm).

4. Describe the Z-scheme of photosynthetic electron transport (overall path).

   Electrons flow: H2O → PSII (P680) → pheophytin → plastoquinone (QA, QB) → cytochrome b6f → plastocyanin → PSI (P700) → A0 → A1 → Fe-S clusters → ferredoxin → FNR → NADP+ → NADPH.

5. What is the role of the oxygen-evolving complex (OEC), and what metal cluster does it contain?

   The OEC on the lumenal side of PSII oxidizes water to O2, releasing electrons, protons, and oxygen. It contains a Mn4CaO5 cluster and cycles through S0–S4 oxidation states (Kok cycle).

6. How does cyclic electron flow around PSI differ from linear electron flow in its products?

   Cyclic electron flow involves only PSI; electrons cycle from ferredoxin back to the cytochrome b6f complex and plastocyanin, generating a proton gradient (ATP) but no NADPH and no O2 evolution.

7. What is non-photochemical quenching (NPQ) and its main rapid component?

   NPQ is the dissipation of excess absorbed light energy as heat to protect the photosynthetic apparatus. Its major rapid component is qE (energy-dependent quenching), triggered by low lumen pH (high ΔpH).

8. Describe the xanthophyll cycle and its role in photoprotection.

   Under high light and low lumen pH, violaxanthin is converted (de-epoxidized) to antheraxanthin and then zeaxanthin by violaxanthin de-epoxidase. Zeaxanthin promotes thermal dissipation (qE). In low light, zeaxanthin is epoxidized back to violaxanthin.

9. What is the PsbS protein's role in photoprotection?

   PsbS is a PSII subunit that senses lumen acidification (via protonation of glutamate residues) and is essential for triggering qE-type non-photochemical quenching.

10. Write the overall equation of the Calvin cycle's carboxylation step and name the enzyme.

    RuBP (5C) + CO2 → 2 molecules of 3-phosphoglycerate (3-PGA, 3C each), catalyzed by Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase).

11. How many ATP and NADPH are required to fix one CO2 (net) in the Calvin cycle, and to make one glucose?

    Per CO2: 3 ATP and 2 NADPH. To make one glucose (6 CO2 fixed): 18 ATP and 12 NADPH.

12. What is the first stable product and CO2-fixing enzyme of the C4 pathway?

    The first stable product is oxaloacetate (4C); the CO2-fixing enzyme in mesophyll cells is PEP carboxylase (PEPcase), which fixes HCO3- onto phosphoenolpyruvate.

13. Compare the leaf anatomy and CO2 fixation site of C3 versus C4 plants.

    C3: Calvin cycle in mesophyll cells, no special anatomy. C4: Kranz anatomy with PEP carboxylase fixing CO2 in mesophyll, then Calvin cycle (Rubisco) confined to bundle sheath cells, concentrating CO2 there.

14. How does CAM photosynthesis separate carbon fixation temporally?

    CAM plants open stomata at night, fixing CO2 via PEP carboxylase into malate stored in vacuoles; during the day stomata close and malate is decarboxylated to release CO2 for the Calvin cycle (Rubisco).

15. Why do C4 and CAM plants minimize photorespiration?

    Both concentrate CO2 around Rubisco (spatially in C4, temporally in CAM), raising the CO2:O2 ratio so Rubisco favors carboxylation over oxygenation, suppressing photorespiration.

16. What is the net ATP/NADH/FADH2 yield of one turn of the citric acid cycle (per acetyl-CoA)?

    3 NADH, 1 FADH2, 1 GTP (or ATP), and 2 CO2 released per acetyl-CoA oxidized.

17. Name the enzyme and reaction that commits acetyl-CoA into the citric acid cycle.

    Citrate synthase condenses acetyl-CoA (2C) with oxaloacetate (4C) to form citrate (6C).

18. Which three citric acid cycle enzymes catalyze the regulated/irreversible steps?

    Citrate synthase, isocitrate dehydrogenase, and the α-ketoglutarate dehydrogenase complex are the key regulatory (rate-controlling) enzymes.

19. List the four complexes and mobile carriers of the plant mitochondrial electron transport chain.

    Complex I (NADH dehydrogenase), Complex II (succinate dehydrogenase), Complex III (cytochrome bc1), Complex IV (cytochrome c oxidase); mobile carriers are ubiquinone (Q) and cytochrome c. ATP is made by Complex V (ATP synthase).

20. What unique 'external' and 'rotenone-insensitive' NAD(P)H dehydrogenases exist in plant mitochondria?

    Plant mitochondria have alternative (type II) NAD(P)H dehydrogenases on both the matrix (internal, rotenone-insensitive) and cytosolic (external) faces of the inner membrane that bypass Complex I and do not pump protons.

21. State the chemiosmotic basis of mitochondrial ATP synthesis.

    Electron transport pumps protons across the inner membrane creating a proton-motive force (ΔpH + membrane potential); protons flow back through ATP synthase (F0F1), driving ATP synthesis (Mitchell's chemiosmotic theory).

22. What is the alternative oxidase (AOX) and where does it branch from the chain?

    AOX is a cyanide-resistant terminal oxidase in plant mitochondria that accepts electrons directly from ubiquinol and reduces O2 to water, bypassing Complexes III and IV (no proton pumping, energy released as heat).

23. What is the physiological significance of the alternative oxidase pathway?

    It allows continued carbon flux/respiration when the cytochrome path is restricted, prevents over-reduction of the ubiquinone pool and ROS formation, and generates heat (thermogenesis, e.g., in Arum spadix).

24. What triggers the oxygenase activity of Rubisco that initiates photorespiration?

    When O2 competes with CO2 at Rubisco's active site (high O2/CO2 ratio, e.g., closed stomata, high temperature), Rubisco adds O2 to RuBP, producing one 3-PGA and one 2-phosphoglycolate (2C).

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