Photosynthesis In Higher Plants

Statement I: Correct. RuBisCO exhibits oxygenase activity under low concentrations, leading to photorespiration. This is a well-documented property of the enzyme.

Statement II: Correct. In plants, the Calvin cycle is specifically localized in the bundle sheath cells' chloroplasts, while initial carbon fixation occurs in mesophyll cells.

Statement III: Incorrect. Yeast fermentation produces ethanol, and when concentrations reach approximately 7%, it becomes toxic to the yeast cells, inhibiting their growth.

Statement IV: Correct. In aerobic respiration's electron transport chain, oxygen serves as the terminal electron acceptor, combining with electrons and protons to form water.

(B) Statements I & IV are correct, III is wrong -

In plants, the cycle (Calvin cycle) occurs specifically in the bundle sheath cells. These cells are adapted to maintain high concentrations of due to the spatial separation of carbon fixation (which happens in mesophyll cells) and the Calvin cycle. The pathway initially fixes carbon in mesophyll cells as oxaloacetate (a 4-carbon compound), which is then transported to bundle sheath cells where is released for use in the cycle.

Thus, the correct answer is (B) Bundle sheath cells, as they are the site of the cycle in plants.

The photolysis of water during photosynthesis is a critical step in the light-dependent reactions, occurring in the oxygen-evolving complex (OEC) of Photosystem II. This process requires specific elements as cofactors. Manganese (Mn) is essential for the OEC's structure and function, while Chlorine (Cl) helps stabilize the manganese cluster and maintains ionic balance.

Thus, the correct answer is (A) Mn and Cl, as these elements are directly involved in the water-splitting reaction. Deficiencies in either Mn or Cl would disrupt the photolysis of water.

Photosynthetically Active Radiation (PAR) refers to the range of wavelengths of light that are used by plants for photosynthesis. It includes primarily the visible light spectrum (400-700 nm). When light strikes a plant, only a portion of it is absorbed by the chlorophyll pigments in the plant's cells for the process of photosynthesis.

On average, plants are capable of capturing and utilizing around 2 to 10 percent of the incoming PAR for photosynthesis. The remaining percentage of light is either reflected or transmitted through the plant. The efficiency of light capture and utilization can vary depending on various factors such as plant species, environmental conditions, and the availability of other resources like water and nutrients.

Matching photosynthetic pigments with their chromatographic colors:

1. Chlorophyll 'b' - t. Yellow green: This accessory pigment appears yellow-green in chromatography.

2. Carotenoids - p. Yellow orange: These accessory pigments (including β-carotene) show bright yellow-orange hues.

3. Chlorophyll 'a' - s. Blue green: The primary photosynthetic pigment appears blue-green on chromatograms.

4. Xanthophylls - r. Yellow: These oxygenated carotenoids (e.g., lutein) appear distinctly yellow.

The correct matching is: (B) 1-t, 2-p, 3-s, 4-r

Other options are incorrect because: - (A) Mismatches all pigment colors - (B) Incorrectly assigns colors to chlorophylls - (D) Reverses chlorophyll 'a' and xanthophyll colors