Chapter 11 of Class 11 Biology is Photosynthesis in Higher Plants. It covers the light and dark reactions of photosynthesis, photosynthetic pigments, and factors affecting the rate of photosynthesis. These Class 11 Biology Chapter 11 solutions are also useful as quick revision notes before exams.
Overview of Photosynthesis
The process by which green plants convert light energy into chemical energy, synthesizing glucose from CO₂ and H₂O, releasing O₂: 6CO₂+12H₂O → C₆H₁₂O₆+6O₂+6H₂O (light). Occurs in chloroplasts.
Photosynthetic Pigments
Chlorophyll a (primary pigment), chlorophyll b, xanthophylls, and carotenoids (accessory pigments) absorb light at different wavelengths, studied via absorption and action spectra.
Light Reactions
Occur in the thylakoid membrane. Involves two photosystems: PSII (absorbs at 680nm, splits water — photolysis, releasing O₂) and PSI (absorbs at 700nm). Produces ATP and NADPH (assimilatory power) via the electron transport chain.
Dark Reactions (Calvin Cycle / C3 Cycle)
Occurs in the stroma, does not directly require light but uses ATP+NADPH from light reactions. Three phases: carboxylation (CO₂ fixation by RuBisCO onto RuBP, forming 3-PGA), reduction (3-PGA → G3P, using ATP+NADPH), regeneration (RuBP regenerated to continue the cycle).
C4 Pathway
Found in plants like maize, sugarcane (adapted to hot, dry climates). CO₂ is first fixed into a 4-carbon compound (oxaloacetate) in mesophyll cells via PEP carboxylase, then transported to bundle sheath cells for the Calvin cycle, minimizing photorespiration.
Factors Affecting Photosynthesis
Light intensity, CO₂ concentration, temperature, and water availability act as limiting factors (Blackman’s Law of Limiting Factors: the rate is limited by whichever factor is in shortest supply).
Class 11 Biology Chapter 11 – Notes and Extra Questions
Along with these NCERT Solutions, students can also use the Class 11 Biology Chapter 11 Extra Questions and Class 11 Biology Chapter 11 Revision Notes for quick revision and extra practice.
